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Author SHA1 Message Date
Kairui Song
d3852f9692 mm, swap: drop the SWAP_HAS_CACHE flag 
Now, the swap cache is managed by the swap table.  All swap cache users
are checking the swap table directly to check the swap cache state. 
SWAP_HAS_CACHE is now just a temporary pin before the first increase from
0 to 1 of a slot's swap count (swap_dup_entries) after swap allocation
(folio_alloc_swap), or before the final free of slots pinned by folio in
swap cache (put_swap_folio).

Drop these two usages.  For the first dup, SWAP_HAS_CACHE pinning was hard
to kill because it used to have multiple meanings, more than just "a slot
is cached".  We have just simplified that and defined that the first dup
is always done with folio locked in swap cache (folio_dup_swap), so stop
checking the SWAP_HAS_CACHE bit and just check the swap cache (swap table)
directly, and add a WARN if a swap entry's count is being increased for
the first time while the folio is not in swap cache.

As for freeing, just let the swap cache free all swap entries of a folio
that have a swap count of zero directly upon folio removal.  We have also
just cleaned up batch freeing to check the swap cache usage using the swap
table: a slot with swap cache in the swap table will not be freed until
its cache is gone, and no SWAP_HAS_CACHE bit is involved anymore.  And
besides, the removal of a folio and freeing of the slots are being done in
the same critical section now, which should improve the performance.

After these two changes, SWAP_HAS_CACHE no longer has any users.  Swap
cache synchronization is also done by the swap table directly, so using
SWAP_HAS_CACHE to pin a slot before adding the cache is also no longer
needed.  Remove all related logic and helpers.  swap_map is now only used
for tracking the count, so all swap_map users can just read it directly,
ignoring the swap_count helper, which was previously used to filter out
the SWAP_HAS_CACHE bit.

The idea of dropping SWAP_HAS_CACHE and using the swap table directly was
initially from Chris's idea of merging all the metadata usage of all swaps
into one place.

Link: https://lkml.kernel.org/r/20251220-swap-table-p2-v5-18-8862a265a033@tencent.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Suggested-by: Chris Li <chrisl@kernel.org>
Reviewed-by: Baoquan He <bhe@redhat.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Rafael J. Wysocki (Intel) <rafael@kernel.org>
Cc: Yosry Ahmed <yosry.ahmed@linux.dev>
Cc: Deepanshu Kartikey <kartikey406@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kairui Song <ryncsn@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-01-31 14:22:57 -08:00
Kairui Song
4984d746c8 mm, swap: check swap table directly for checking cache 
Instead of looking at the swap map, check swap table directly to tell if a
swap slot is cached.  Prepares for the removal of SWAP_HAS_CACHE.

Link: https://lkml.kernel.org/r/20251220-swap-table-p2-v5-16-8862a265a033@tencent.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Reviewed-by: Baoquan He <bhe@redhat.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Chris Li <chrisl@kernel.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Rafael J. Wysocki (Intel) <rafael@kernel.org>
Cc: Yosry Ahmed <yosry.ahmed@linux.dev>
Cc: Deepanshu Kartikey <kartikey406@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kairui Song <ryncsn@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-01-31 14:22:57 -08:00
Kairui Song
270f095179 mm, swap: add folio to swap cache directly on allocation 
The allocator uses SWAP_HAS_CACHE to pin a swap slot upon allocation. 
SWAP_HAS_CACHE is being deprecated as it caused a lot of confusion.  This
pinning usage here can be dropped by adding the folio to swap cache
directly on allocation.

All swap allocations are folio-based now (except for hibernation), so the
swap allocator can always take the folio as the parameter.  And now both
swap cache (swap table) and swap map are protected by the cluster lock,
scanning the map and inserting the folio can be done in the same critical
section.  This eliminates the time window that a slot is pinned by
SWAP_HAS_CACHE, but it has no cache, and avoids touching the lock multiple
times.

This is both a cleanup and an optimization.

Link: https://lkml.kernel.org/r/20251220-swap-table-p2-v5-15-8862a265a033@tencent.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Reviewed-by: Baoquan He <bhe@redhat.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Chris Li <chrisl@kernel.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Rafael J. Wysocki (Intel) <rafael@kernel.org>
Cc: Yosry Ahmed <yosry.ahmed@linux.dev>
Cc: Deepanshu Kartikey <kartikey406@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kairui Song <ryncsn@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-01-31 14:22:57 -08:00
Kairui Song
3697615914 mm, swap: cleanup swap entry management workflow 
The current swap entry allocation/freeing workflow has never had a clear
definition.  This makes it hard to debug or add new optimizations.

This commit introduces a proper definition of how swap entries would be
allocated and freed.  Now, most operations are folio based, so they will
never exceed one swap cluster, and we now have a cleaner border between
swap and the rest of mm, making it much easier to follow and debug,
especially with new added sanity checks.  Also making more optimization
possible.

Swap entry will be mostly freed and free with a folio bound.  The folio
lock will be useful for resolving many swap related races.

Now swap allocation (except hibernation) always starts with a folio in the
swap cache, and gets duped/freed protected by the folio lock:

- folio_alloc_swap() - The only allocation entry point now.
  Context: The folio must be locked.
  This allocates one or a set of continuous swap slots for a folio and
  binds them to the folio by adding the folio to the swap cache. The
  swap slots' swap count start with zero value.

- folio_dup_swap() - Increase the swap count of one or more entries.
  Context: The folio must be locked and in the swap cache. For now, the
  caller still has to lock the new swap entry owner (e.g., PTL).
  This increases the ref count of swap entries allocated to a folio.
  Newly allocated swap slots' count has to be increased by this helper
  as the folio got unmapped (and swap entries got installed).

- folio_put_swap() - Decrease the swap count of one or more entries.
  Context: The folio must be locked and in the swap cache. For now, the
  caller still has to lock the new swap entry owner (e.g., PTL).
  This decreases the ref count of swap entries allocated to a folio.
  Typically, swapin will decrease the swap count as the folio got
  installed back and the swap entry got uninstalled

  This won't remove the folio from the swap cache and free the
  slot. Lazy freeing of swap cache is helpful for reducing IO.
  There is already a folio_free_swap() for immediate cache reclaim.
  This part could be further optimized later.

The above locking constraints could be further relaxed when the swap table
is fully implemented.  Currently dup still needs the caller to lock the
swap entry container (e.g.  PTL), or a concurrent zap may underflow the
swap count.

Some swap users need to interact with swap count without involving folio
(e.g.  forking/zapping the page table or mapping truncate without swapin).
In such cases, the caller has to ensure there is no race condition on
whatever owns the swap count and use the below helpers:

- swap_put_entries_direct() - Decrease the swap count directly.
  Context: The caller must lock whatever is referencing the slots to
  avoid a race.

  Typically the page table zapping or shmem mapping truncate will need
  to free swap slots directly. If a slot is cached (has a folio bound),
  this will also try to release the swap cache.

- swap_dup_entry_direct() - Increase the swap count directly.
  Context: The caller must lock whatever is referencing the entries to
  avoid race, and the entries must already have a swap count > 1.

  Typically, forking will need to copy the page table and hence needs to
  increase the swap count of the entries in the table. The page table is
  locked while referencing the swap entries, so the entries all have a
  swap count > 1 and can't be freed.

Hibernation subsystem is a bit different, so two special wrappers are here:

- swap_alloc_hibernation_slot() - Allocate one entry from one device.
- swap_free_hibernation_slot() - Free one entry allocated by the above
  helper.

All hibernation entries are exclusive to the hibernation subsystem and
should not interact with ordinary swap routines.

By separating the workflows, it will be possible to bind folio more
tightly with swap cache and get rid of the SWAP_HAS_CACHE as a temporary
pin.

This commit should not introduce any behavior change

[kasong@tencent.com: fix leak, per Chris Mason.  Remove WARN_ON, per Lai Yi]
  Link: https://lkml.kernel.org/r/CAMgjq7AUz10uETVm8ozDWcB3XohkOqf0i33KGrAquvEVvfp5cg@mail.gmail.com
[ryncsn@gmail.com: fix KSM copy pages for swapoff, per Chris]
  Link: https://lkml.kernel.org/r/aXxkANcET3l2Xu6J@KASONG-MC4
Link: https://lkml.kernel.org/r/20251220-swap-table-p2-v5-14-8862a265a033@tencent.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Signed-off-by: Kairui Song <ryncsn@gmail.com>
Acked-by: Rafael J. Wysocki (Intel) <rafael@kernel.org>
Reviewed-by: Baoquan He <bhe@redhat.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Chris Li <chrisl@kernel.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Yosry Ahmed <yosry.ahmed@linux.dev>
Cc: Deepanshu Kartikey <kartikey406@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kairui Song <ryncsn@gmail.com>
Cc: Chris Mason <clm@fb.com>
Cc: Chris Mason <clm@meta.com>
Cc: Lai Yi <yi1.lai@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-01-31 14:22:56 -08:00
Kairui Song
de85024b34 mm, swap: remove workaround for unsynchronized swap map cache state 
Remove the "skip if exists" check from commit a65b0e7607 ("zswap: make
shrinking memcg-aware").  It was needed because there is a tiny time
window between setting the SWAP_HAS_CACHE bit and actually adding the
folio to the swap cache.  If a user is trying to add the folio into the
swap cache but another user was interrupted after setting SWAP_HAS_CACHE
but hasn't added the folio to the swap cache yet, it might lead to a
deadlock.

We have moved the bit setting to the same critical section as adding the
folio, so this is no longer needed.  Remove it and clean it up.

Link: https://lkml.kernel.org/r/20251220-swap-table-p2-v5-13-8862a265a033@tencent.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Reviewed-by: Baoquan He <bhe@redhat.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Chris Li <chrisl@kernel.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Rafael J. Wysocki (Intel) <rafael@kernel.org>
Cc: Yosry Ahmed <yosry.ahmed@linux.dev>
Cc: Deepanshu Kartikey <kartikey406@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kairui Song <ryncsn@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-01-31 14:22:56 -08:00
Kairui Song
2732acda82 mm, swap: use swap cache as the swap in synchronize layer 
Current swap in synchronization mostly uses the swap_map's SWAP_HAS_CACHE
bit.  Whoever sets the bit first does the actual work to swap in a folio.

This has been causing many issues as it's just a poor implementation of a
bit lock.  Raced users have no idea what is pinning a slot, so it has to
loop with a schedule_timeout_uninterruptible(1), which is ugly and causes
long-tailing or other performance issues.  Besides, the abuse of
SWAP_HAS_CACHE has been causing many other troubles for synchronization or
maintenance.

This is the first step to remove this bit completely.

Now all swap in paths are using the swap cache, and both the swap cache
and swap map are protected by the cluster lock.  So we can just resolve
the swap synchronization with the swap cache layer directly using the
cluster lock and folio lock.  Whoever inserts a folio in the swap cache
first does the swap in work.  And because folios are locked during swap
operations, other raced swap operations will just wait on the folio lock.

The SWAP_HAS_CACHE will be removed in later commit.  For now, we still set
it for some remaining users.  But now we do the bit setting and swap cache
folio adding in the same critical section, after swap cache is ready.  No
one will have to spin on the SWAP_HAS_CACHE bit anymore.

This both simplifies the logic and should improve the performance,
eliminating issues like the one solved in commit 01626a1823 ("mm: avoid
unconditional one-tick sleep when swapcache_prepare fails"), or the
"skip_if_exists" from commit a65b0e7607 ("zswap: make shrinking
memcg-aware"), which will be removed very soon.

[kasong@tencent.com: fix cgroup v1 accounting issue]
 Link: https://lkml.kernel.org/r/CAMgjq7CGUnzOVG7uSaYjzw9wD7w2dSKOHprJfaEp4CcGLgE3iw@mail.gmail.com
Link: https://lkml.kernel.org/r/20251220-swap-table-p2-v5-12-8862a265a033@tencent.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Reviewed-by: Baoquan He <bhe@redhat.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Chris Li <chrisl@kernel.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Rafael J. Wysocki (Intel) <rafael@kernel.org>
Cc: Yosry Ahmed <yosry.ahmed@linux.dev>
Cc: Deepanshu Kartikey <kartikey406@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kairui Song <ryncsn@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-01-31 14:22:56 -08:00
Kairui Song
c246d236b1 mm/shmem: never bypass the swap cache for SWP_SYNCHRONOUS_IO 
Now the overhead of the swap cache is trivial to none, bypassing the swap
cache is no longer a good optimization.

We have removed the cache bypass swapin for anon memory, now do the same
for shmem.  Many helpers and functions can be dropped now.

The performance may slightly drop because of the co-existence and double
update of swap_map and swap table, and this problem will be improved very
soon in later commits by dropping the swap_map update partially:

Swapin of 24 GB file with tmpfs with
transparent_hugepage_tmpfs=within_size and ZRAM, 3 test runs on my
machine:

Before:  After this commit:  After this series:
5.99s    6.29s               6.08s

And later swap table phases will drop the swap_map completely to avoid
overhead and reduce memory usage.

Link: https://lkml.kernel.org/r/20251219195751.61328-1-ryncsn@gmail.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Tested-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Chris Li <chrisl@kernel.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Rafael J. Wysocki (Intel) <rafael@kernel.org>
Cc: Yosry Ahmed <yosry.ahmed@linux.dev>
Cc: Deepanshu Kartikey <kartikey406@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-01-31 14:22:54 -08:00
Kairui Song
f1879e8a0c mm, swap: never bypass the swap cache even for SWP_SYNCHRONOUS_IO 
Now the overhead of the swap cache is trivial.  Bypassing the swap cache
is no longer a valid optimization.  So unify the swapin path using the
swap cache.  This changes the swap in behavior in two observable ways.

Readahead is now always disabled for SWP_SYNCHRONOUS_IO devices, which is
a huge win for some workloads: We used to rely on `SWP_SYNCHRONOUS_IO &&
__swap_count(entry) == 1` as the indicator to bypass both the swap cache
and readahead, the swap count check made bypassing ineffective in many
cases, and it's not a good indicator.  The limitation existed because the
current swap design made it hard to decouple readahead bypassing and swap
cache bypassing.  We do want to always bypass readahead for
SWP_SYNCHRONOUS_IO devices, but bypassing swap cache at the same time will
cause repeated IO and memory overhead.  Now that swap cache bypassing is
gone, this swap count check can be dropped.

The second thing here is that this enabled large swapin for all swap
entries on SWP_SYNCHRONOUS_IO devices.  Previously, the large swap in is
also coupled with swap cache bypassing, and so the swap count checking
also makes large swapin less effective.  Now this is also improved.  We
will always have large swapin supported for all SWP_SYNCHRONOUS_IO cases.

And to catch potential issues with large swapin, especially with page
exclusiveness and swap cache, more debug sanity checks and comments are
added.  But overall, the code is simpler.  And new helper and routines
will be used by other components in later commits too.  And now it's
possible to rely on the swap cache layer for resolving synchronization
issues, which will also be done by a later commit.

Worth mentioning that for a large folio workload, this may cause more
serious thrashing.  This isn't a problem with this commit, but a generic
large folio issue.  For a 4K workload, this commit increases the
performance.

Link: https://lkml.kernel.org/r/20251220-swap-table-p2-v5-3-8862a265a033@tencent.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Reviewed-by: Baoquan He <bhe@redhat.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Chris Li <chrisl@kernel.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Rafael J. Wysocki (Intel) <rafael@kernel.org>
Cc: Yosry Ahmed <yosry.ahmed@linux.dev>
Cc: Deepanshu Kartikey <kartikey406@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kairui Song <ryncsn@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-01-31 14:22:53 -08:00
Kairui Song
d7cf0d54f2 mm, swap: rename __read_swap_cache_async to swap_cache_alloc_folio 
Patch series "mm, swap: swap table phase II: unify swapin use", v5.

This series removes the SWP_SYNCHRONOUS_IO swap cache bypass swapin code
and special swap flag bits including SWAP_HAS_CACHE, along with many
historical issues.  The performance is about ~20% better for some
workloads, like Redis with persistence.  This also cleans up the code to
prepare for later phases, some patches are from a previously posted
series.

Swap cache bypassing and swap synchronization in general had many issues. 
Some are solved as workarounds, and some are still there [1].  To resolve
them in a clean way, one good solution is to always use swap cache as the
synchronization layer [2].  So we have to remove the swap cache bypass
swap-in path first.  It wasn't very doable due to performance issues, but
now combined with the swap table, removing the swap cache bypass path will
instead improve the performance, there is no reason to keep it.

Now we can rework the swap entry and cache synchronization following the
new design.  Swap cache synchronization was heavily relying on
SWAP_HAS_CACHE, which is the cause of many issues.  By dropping the usage
of special swap map bits and related workarounds, we get a cleaner code
base and prepare for merging the swap count into the swap table in the
next step.

And swap_map is now only used for swap count, so in the next phase,
swap_map can be merged into the swap table, which will clean up more
things and start to reduce the static memory usage.  Removal of
swap_cgroup_ctrl is also doable, but needs to be done after we also
simplify the allocation of swapin folios: always use the new
swap_cache_alloc_folio helper so the accounting will also be managed by
the swap layer by then.

Test results:

Redis / Valkey bench:
=====================

Testing on a ARM64 VM 1.5G memory:
Server: valkey-server --maxmemory 2560M
Client: redis-benchmark -r 3000000 -n 3000000 -d 1024 -c 12 -P 32 -t get

        no persistence              with BGSAVE
Before: 460475.84 RPS               311591.19 RPS
After:  451943.34 RPS (-1.9%)       371379.06 RPS (+19.2%)

Testing on a x86_64 VM with 4G memory (system components takes about 2G):
Server:
Client: redis-benchmark -r 3000000 -n 3000000 -d 1024 -c 12 -P 32 -t get

        no persistence              with BGSAVE
Before: 306044.38 RPS               102745.88 RPS
After:  309645.44 RPS (+1.2%)       125313.28 RPS (+22.0%)

The performance is a lot better when persistence is applied.  This should
apply to many other workloads that involve sharing memory and COW.  A
slight performance drop was observed for the ARM64 Redis test: We are
still using swap_map to track the swap count, which is causing redundant
cache and CPU overhead and is not very performance-friendly for some
arches.  This will be improved once we merge the swap map into the swap
table (as already demonstrated previously [3]).

vm-scabiity
===========
usemem --init-time -O -y -x -n 32 1536M (16G memory, global pressure,
simulated PMEM as swap), average result of 6 test run:

                           Before:         After:
System time:               282.22s         283.47s
Sum Throughput:            5677.35 MB/s    5688.78 MB/s
Single process Throughput: 176.41 MB/s     176.23 MB/s
Free latency:              518477.96 us    521488.06 us

Which is almost identical.

Build kernel test:
==================
Test using ZRAM as SWAP, make -j48, defconfig, on a x86_64 VM
with 4G RAM, under global pressure, avg of 32 test run:

                Before            After:
System time:    1379.91s          1364.22s (-0.11%)

Test using ZSWAP with NVME SWAP, make -j48, defconfig, on a x86_64 VM
with 4G RAM, under global pressure, avg of 32 test run:

                Before            After:
System time:    1822.52s          1803.33s (-0.11%)

Which is almost identical.

MySQL:
======
sysbench /usr/share/sysbench/oltp_read_only.lua --tables=16
--table-size=1000000 --threads=96 --time=600 (using ZRAM as SWAP, in a
512M memory cgroup, buffer pool set to 3G, 3 test run and 180s warm up).

Before: 318162.18 qps
After:  318512.01 qps (+0.01%)

In conclusion, the result is looking better or identical for most cases,
and it's especially better for workloads with swap count > 1 on SYNC_IO
devices, about ~20% gain in above test.  Next phases will start to merge
swap count into swap table and reduce memory usage.

One more gain here is that we now have better support for THP swapin. 
Previously, the THP swapin was bound with swap cache bypassing, which only
works for single-mapped folios.  Removing the bypassing path also enabled
THP swapin for all folios.  The THP swapin is still limited to SYNC_IO
devices, the limitation can be removed later.

This may cause more serious THP thrashing for certain workloads, but
that's not an issue caused by this series, it's a common THP issue we
should resolve separately.


This patch (of 19):

__read_swap_cache_async is widely used to allocate and ensure a folio is
in swapcache, or get the folio if a folio is already there.

It's not async, and it's not doing any read.  Rename it to better present
its usage, and prepare to be reworked as part of new swap cache APIs.

Also, add some comments for the function.  Worth noting that the
skip_if_exists argument is an long existing workaround that will be
dropped soon.

Link: https://lkml.kernel.org/r/20251220-swap-table-p2-v5-0-8862a265a033@tencent.com
Link: https://lkml.kernel.org/r/20251220-swap-table-p2-v5-1-8862a265a033@tencent.com
Link: https://lore.kernel.org/linux-mm/CAMgjq7D5qoFEK9Omvd5_Zqs6M+TEoG03+2i_mhuP5CQPSOPrmQ@mail.gmail.com/ [1]
Link: https://lore.kernel.org/linux-mm/20240326185032.72159-1-ryncsn@gmail.com/ [2]
Link: https://lore.kernel.org/linux-mm/20250514201729.48420-1-ryncsn@gmail.com/ [3]
Signed-off-by: Kairui Song <kasong@tencent.com>
Reviewed-by: Yosry Ahmed <yosry.ahmed@linux.dev>
Acked-by: Chris Li <chrisl@kernel.org>
Reviewed-by: Barry Song <baohua@kernel.org>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Reviewed-by: Baoquan He <bhe@redhat.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Rafael J. Wysocki (Intel) <rafael@kernel.org>
Cc: Deepanshu Kartikey <kartikey406@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-01-31 14:22:53 -08:00
Andrew Morton
f84b65b045 Merge branch 'mm-hotfixes-stable' into mm-stable to pick up "mm/shmem, 
swap: fix race of truncate and swap entry split", needed for merging "mm,
swap: cleanup swap entry management workflow".
 2026-01-31 14:20:03 -08:00
robin.kuo
a0f3c0845a mm, swap: restore swap_space attr aviod kernel panic 
commit 8b47299a41 ("mm, swap: mark swap address space ro and add context
debug check") made the swap address space read-only.  It may lead to
kernel panic if arch_prepare_to_swap returns a failure under heavy memory
pressure as follows,

el1_abort+0x40/0x64
el1h_64_sync_handler+0x48/0xcc
el1h_64_sync+0x84/0x88
errseq_set+0x4c/0xb8 (P)
__filemap_set_wb_err+0x20/0xd0
shrink_folio_list+0xc20/0x11cc
evict_folios+0x1520/0x1be4
try_to_shrink_lruvec+0x27c/0x3dc
shrink_one+0x9c/0x228
shrink_node+0xb3c/0xeac
do_try_to_free_pages+0x170/0x4f0
try_to_free_pages+0x334/0x534
__alloc_pages_direct_reclaim+0x90/0x158
__alloc_pages_slowpath+0x334/0x588
__alloc_frozen_pages_noprof+0x224/0x2fc
__folio_alloc_noprof+0x14/0x64
vma_alloc_zeroed_movable_folio+0x34/0x44
do_pte_missing+0xad4/0x1040
handle_mm_fault+0x4a4/0x790
do_page_fault+0x288/0x5f8
do_translation_fault+0x38/0x54
do_mem_abort+0x54/0xa8

Restore swap address space as not ro to avoid the panic.

Link: https://lkml.kernel.org/r/20260116062535.306453-2-robin.kuo@mediatek.com
Fixes: 8b47299a41 ("mm, swap: mark swap address space ro and add context debug check")
Signed-off-by: robin.kuo <robin.kuo@mediatek.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: andrew.yang <andrew.yang@mediatek.com>
Cc: AngeloGiaocchino Del Regno <angelogioacchino.delregno@collabora.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Chinwen Chang <chinwen.chang@mediatek.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: Kairui Song <kasong@tencent.com>
Cc: Kairui Song <ryncsn@gmail.com>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: Mathias Brugger <matthias.bgg@gmail.com>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Qun-wei Lin <Qun-wei.Lin@mediatek.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-01-26 19:03:45 -08:00
Kevin Lourenco
62451ae347 mm: fix minor spelling mistakes in comments 
Correct several typos in comments across files in mm/

[akpm@linux-foundation.org: also fix comment grammar, per SeongJae]
Link: https://lkml.kernel.org/r/20251218150906.25042-1-klourencodev@gmail.com
Signed-off-by: Kevin Lourenco <klourencodev@gmail.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Acked-by: David Hildenbrand (Red Hat) <david@kernel.org>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-01-20 19:24:48 -08:00
Kairui Song
ab61de9b78 mm/migrate, swap: drop usage of folio_index 
This helper was used when swap cache was mixed with page cache.  Now they
are completely separate from each other, access to the swap cache is all
wrapped by the swap_cache_* helpers, which expect the folio's swap entry
as a parameter.

This helper is no longer used, remove the last redundant user and drop it.

Link: https://lkml.kernel.org/r/20251024-swap-clean-after-swap-table-p1-v2-4-a709469052e7@tencent.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Acked-by: Chris Li <chrisl@kernel.org>
Acked-by: Nhat Pham <nphamcs@gmail.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Barry Song <baohua@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2025-11-16 17:28:20 -08:00
Kairui Song
07adc4cf1e mm, swap: implement dynamic allocation of swap table 
Now swap table is cluster based, which means free clusters can free its
table since no one should modify it.

There could be speculative readers, like swap cache look up, protect them
by making them RCU protected.  All swap table should be filled with null
entries before free, so such readers will either see a NULL pointer or a
null filled table being lazy freed.

On allocation, allocate the table when a cluster is used by any order.

This way, we can reduce the memory usage of large swap device
significantly.

This idea to dynamically release unused swap cluster data was initially
suggested by Chris Li while proposing the cluster swap allocator and it
suits the swap table idea very well.

Link: https://lkml.kernel.org/r/20250916160100.31545-15-ryncsn@gmail.com
Co-developed-by: Chris Li <chrisl@kernel.org>
Signed-off-by: Chris Li <chrisl@kernel.org>
Signed-off-by: Kairui Song <kasong@tencent.com>
Suggested-by: Chris Li <chrisl@kernel.org>
Reviewed-by: Barry Song <baohua@kernel.org>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: kernel test robot <oliver.sang@intel.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2025-09-21 14:22:25 -07:00
Kairui Song
685a17fbd3 mm, swap: remove contention workaround for swap cache 
Swap cluster setup will try to shuffle the clusters on initialization.  It
was helpful to avoid contention for the swap cache space.  The cluster
size (2M) was much smaller than each swap cache space (64M), so shuffling
the cluster means the allocator will try to allocate swap slots that are
in different swap cache spaces for each CPU, reducing the chance of two
CPUs using the same swap cache space, and hence reducing the contention.

Now, swap cache is managed by swap clusters, this shuffle is pointless. 
Just remove it, and clean up related macros.

This also improves the HDD swap performance as shuffling IO is a bad idea
for HDD, and now the shuffling is gone.  Test have shown a ~40%
performance gain for HDD [1]:

Doing sequential swap in of 8G data using 8 processes with usemem, average
of 3 test runs:

Before: 1270.91 KB/s per process
After:  1849.54 KB/s per process

Link: https://lore.kernel.org/linux-mm/CAMgjq7AdauQ8=X0zeih2r21QoV=-WWj1hyBxLWRzq74n-C=-Ng@mail.gmail.com/ [1]
Link: https://lkml.kernel.org/r/20250916160100.31545-14-ryncsn@gmail.com
Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202504241621.f27743ec-lkp@intel.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Acked-by: Chris Li <chrisl@kernel.org>
Reviewed-by: Barry Song <baohua@kernel.org>
Acked-by: David Hildenbrand <david@redhat.com>
Suggested-by: Chris Li <chrisl@kernel.org>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2025-09-21 14:22:25 -07:00
Kairui Song
8b47299a41 mm, swap: mark swap address space ro and add context debug check 
Swap cache is now backed by swap table, and the address space is not
holding any mutable data anymore.  And swap cache is now protected by the
swap cluster lock, instead of the XArray lock.  All access to swap cache
are wrapped by swap cache helpers.  Locking is mostly handled internally
by swap cache helpers, only a few __swap_cache_* helpers require the
caller to lock the cluster by themselves.

Worth noting that, unlike XArray, the cluster lock is not IRQ safe.  The
swap cache was very different compared to filemap, and now it's completely
separated from filemap.  Nothing wants to mark or change anything or do a
writeback callback in IRQ.

So explicitly document this and add a debug check to avoid further
potential misuse.  And mark the swap cache space as read-only to avoid any
user wrongly mixing unexpected filemap helpers with swap cache.

Link: https://lkml.kernel.org/r/20250916160100.31545-13-ryncsn@gmail.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Acked-by: Chris Li <chrisl@kernel.org>
Acked-by: David Hildenbrand <david@redhat.com>
Suggested-by: Chris Li <chrisl@kernel.org>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Barry Song <baohua@kernel.org>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: kernel test robot <oliver.sang@intel.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2025-09-21 14:22:25 -07:00
Kairui Song
8578e0c00d mm, swap: use the swap table for the swap cache and switch API 
Introduce basic swap table infrastructures, which are now just a
fixed-sized flat array inside each swap cluster, with access wrappers.

Each cluster contains a swap table of 512 entries.  Each table entry is an
opaque atomic long.  It could be in 3 types: a shadow type (XA_VALUE), a
folio type (pointer), or NULL.

In this first step, it only supports storing a folio or shadow, and it is
a drop-in replacement for the current swap cache.  Convert all swap cache
users to use the new sets of APIs.  Chris Li has been suggesting using a
new infrastructure for swap cache for better performance, and that idea
combined well with the swap table as the new backing structure.  Now the
lock contention range is reduced to 2M clusters, which is much smaller
than the 64M address_space.  And we can also drop the multiple
address_space design.

All the internal works are done with swap_cache_get_* helpers.  Swap cache
lookup is still lock-less like before, and the helper's contexts are same
with original swap cache helpers.  They still require a pin on the swap
device to prevent the backing data from being freed.

Swap cache updates are now protected by the swap cluster lock instead of
the XArray lock.  This is mostly handled internally, but new
__swap_cache_* helpers require the caller to lock the cluster.  So, a few
new cluster access and locking helpers are also introduced.

A fully cluster-based unified swap table can be implemented on top of this
to take care of all count tracking and synchronization work, with dynamic
allocation.  It should reduce the memory usage while making the
performance even better.

Link: https://lkml.kernel.org/r/20250916160100.31545-12-ryncsn@gmail.com
Co-developed-by: Chris Li <chrisl@kernel.org>
Signed-off-by: Chris Li <chrisl@kernel.org>
Signed-off-by: Kairui Song <kasong@tencent.com>
Acked-by: Chris Li <chrisl@kernel.org>
Suggested-by: Chris Li <chrisl@kernel.org>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Barry Song <baohua@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: kernel test robot <oliver.sang@intel.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2025-09-21 14:22:24 -07:00
Kairui Song
094dc8b059 mm, swap: wrap swap cache replacement with a helper 
There are currently three swap cache users that are trying to replace an
existing folio with a new one: huge memory splitting, migration, and shmem
replacement.  What they are doing is quite similar.

Introduce a common helper for this.  In later commits, this can be easily
switched to use the swap table by updating this helper.

The newly added helper also makes the swap cache API better defined, and
make debugging easier by adding a few more debug checks.

Migration and shmem replace are meant to clone the folio, including
content, swap entry value, and flags.  And splitting will adjust each sub
folio's swap entry according to order, which could be non-uniform in the
future.  So document it clearly that it's the caller's responsibility to
set up the new folio's swap entries and flags before calling the helper. 
The helper will just follow the new folio's entry value.

This also prepares for replacing high-order folios in the swap cache. 
Currently, only splitting to order 0 is allowed for swap cache folios. 
Using the new helper, we can handle high-order folio splitting better.

Link: https://lkml.kernel.org/r/20250916160100.31545-11-ryncsn@gmail.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Chris Li <chrisl@kernel.org>
Suggested-by: Chris Li <chrisl@kernel.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: Barry Song <baohua@kernel.org>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: kernel test robot <oliver.sang@intel.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2025-09-21 14:22:24 -07:00
Kairui Song
fd8d4f862f mm, swap: cleanup swap cache API and add kerneldoc 
In preparation for replacing the swap cache backend with the swap table,
clean up and add proper kernel doc for all swap cache APIs.  Now all swap
cache APIs are well-defined with consistent names.

No feature change, only renaming and documenting.

Link: https://lkml.kernel.org/r/20250916160100.31545-9-ryncsn@gmail.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Acked-by: Chris Li <chrisl@kernel.org>
Reviewed-by: Barry Song <baohua@kernel.org>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Acked-by: David Hildenbrand <david@redhat.com>
Suggested-by: Chris Li <chrisl@kernel.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: kernel test robot <oliver.sang@intel.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2025-09-21 14:22:23 -07:00
Kairui Song
0fcf8ef4fd mm, swap: tidy up swap device and cluster info helpers 
swp_swap_info is the most commonly used helper for retrieving swap info. 
It has an internal check that may lead to a NULL return value, but almost
none of its caller checks the return value, making the internal check
pointless.  In fact, most of these callers already ensured the entry is
valid and never expect a NULL value.

Tidy this up and improve the function names.  If the caller can make sure
the swap entry/type is valid and the device is pinned, use the new
introduced __swap_entry_to_info/__swap_type_to_info instead.  They have
more debug sanity checks and lower overhead as they are inlined.

Callers that may expect a NULL value should use
swap_entry_to_info/swap_type_to_info instead.

No feature change.  The rearranged codes should have had no effect, or
they should have been hitting NULL de-ref bugs already.  Only some new
sanity checks are added so potential issues may show up in debug build.

The new helpers will be frequently used with swap table later when working
with swap cache folios.  A locked swap cache folio ensures the entries are
valid and stable so these helpers are very helpful.

Link: https://lkml.kernel.org/r/20250916160100.31545-8-ryncsn@gmail.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Acked-by: Chris Li <chrisl@kernel.org>
Reviewed-by: Barry Song <baohua@kernel.org>
Acked-by: David Hildenbrand <david@redhat.com>
Suggested-by: Chris Li <chrisl@kernel.org>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: kernel test robot <oliver.sang@intel.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2025-09-21 14:22:23 -07:00
Kairui Song
4522aed4ff mm, swap: rename and move some swap cluster definition and helpers 
No feature change, move cluster related definitions and helpers to
mm/swap.h, also tidy up and add a "swap_" prefix for cluster lock/unlock
helpers, so they can be used outside of swap files.  And while at it, add
kerneldoc.

Link: https://lkml.kernel.org/r/20250916160100.31545-7-ryncsn@gmail.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Barry Song <baohua@kernel.org>
Acked-by: Chris Li <chrisl@kernel.org>
Acked-by: David Hildenbrand <david@redhat.com>
Suggested-by: Chris Li <chrisl@kernel.org>
Acked-by: Nhat Pham <nphamcs@gmail.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: kernel test robot <oliver.sang@intel.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Yosry Ahmed <yosryahmed@google.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2025-09-21 14:22:23 -07:00
Kairui Song
ae38eb2105 mm, swap: always lock and check the swap cache folio before use 
Swap cache lookup only increases the reference count of the returned
folio.  That's not enough to ensure a folio is stable in the swap cache,
so the folio could be removed from the swap cache at any time.  The caller
should always lock and check the folio before using it.

We have just documented this in kerneldoc, now introduce a helper for swap
cache folio verification with proper sanity checks.

Also, sanitize a few current users to use this convention and the new
helper for easier debugging.  They were not having observable problems
yet, only trivial issues like wasted CPU cycles on swapoff or reclaiming. 
They would fail in some other way, but it is still better to always follow
this convention to make things robust and make later commits easier to do.

Link: https://lkml.kernel.org/r/20250916160100.31545-6-ryncsn@gmail.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Chris Li <chrisl@kernel.org>
Acked-by: Nhat Pham <nphamcs@gmail.com>
Suggested-by: Chris Li <chrisl@kernel.org>
Reviewed-by: Barry Song <baohua@kernel.org>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: kernel test robot <oliver.sang@intel.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Yosry Ahmed <yosryahmed@google.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2025-09-21 14:22:23 -07:00
Kairui Song
f28124617f mm, swap: use unified helper for swap cache look up 
The swap cache lookup helper swap_cache_get_folio currently does readahead
updates as well, so callers that are not doing swapin from any VMA or
mapping are forced to reuse filemap helpers instead, and have to access
the swap cache space directly.

So decouple readahead update with swap cache lookup.  Move the readahead
update part into a standalone helper.  Let the caller call the readahead
update helper if they do readahead.  And convert all swap cache lookups to
use swap_cache_get_folio.

After this commit, there are only three special cases for accessing swap
cache space now: huge memory splitting, migration, and shmem replacing,
because they need to lock the XArray.  The following commits will wrap
their accesses to the swap cache too, with special helpers.

And worth noting, currently dropbehind is not supported for anon folio,
and we will never see a dropbehind folio in swap cache.  The unified
helper can be updated later to handle that.

While at it, add proper kernedoc for touched helpers.

No functional change.

Link: https://lkml.kernel.org/r/20250916160100.31545-3-ryncsn@gmail.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Barry Song <baohua@kernel.org>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Chris Li <chrisl@kernel.org>
Acked-by: Nhat Pham <nphamcs@gmail.com>
Suggested-by: Chris Li <chrisl@kernel.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: kernel test robot <oliver.sang@intel.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Yosry Ahmed <yosryahmed@google.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2025-09-21 14:22:22 -07:00
Kairui Song
27763edac9 mm/mincore, swap: consolidate swap cache checking for mincore 
Patch series "mm/mincore: minor clean up for swap cache checking".

This series cleans up a swap cache helper only used by mincore, move it
back into mincore code.  Also separate the swap cache related logics out
of shmem / page cache logics in mincore.

With this series we have less lines of code and better performance.

Before this series:
mincore on a swaped out 16G anon mmap range:
Took 488220 us
mincore on 16G shmem mmap range:
Took 530272 us.

After this series:
mincore on a swaped out 16G anon mmap range:
Took 446763 us
mincore on 16G shmem mmap range:
Took 460496 us.

About ~10% faster.


This patch (of 2):

The filemap_get_incore_folio (previously find_get_incore_page) helper was
introduced by commit 61ef186557 ("mm: factor find_get_incore_page out of
mincore_page") to be used by later commit f5df8635c5 ("mm: use
find_get_incore_page in memcontrol"), so memory cgroup charge move code
can be simplified.

But commit 6b611388b6 ("memcg-v1: remove charge move code") removed that
user completely, it's only used by mincore now.

So this commit basically reverts commit 61ef186557 ("mm: factor
find_get_incore_page out of mincore_page").  Move it back to mincore side
to simplify the code.

Link: https://lkml.kernel.org/r/20250811172018.48901-1-ryncsn@gmail.com
Link: https://lkml.kernel.org/r/20250811172018.48901-2-ryncsn@gmail.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Acked-by: Nhat Pham <nphamcs@gmail.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Chris Li <chrisl@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2025-09-13 16:54:49 -07:00
Christoph Hellwig
624043dbd5 mm: stop passing a writeback_control structure to swap_writeout 
swap_writeout only needs the swap_iocb cookie from the writeback_control
structure, so pass it explicitly.

Link: https://lkml.kernel.org/r/20250610054959.2057526-6-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2025-07-09 22:41:58 -07:00
Christoph Hellwig
2ba8ffcefe mm: stop passing a writeback_control structure to __swap_writepage 
__swap_writepage only needs the swap_iocb cookie from the
writeback_control structure, so pass it explicitly and remove the now
unused swap_iocb member from struct writeback_control.

Link: https://lkml.kernel.org/r/20250610054959.2057526-5-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Nhat Pham <nphamcs@gmail.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2025-07-09 22:41:57 -07:00
Kairui Song
a05dd8ae5c mm/shmem, swap: fix softlockup with mTHP swapin 
Following softlockup can be easily reproduced on my test machine with:

echo always > /sys/kernel/mm/transparent_hugepage/hugepages-64kB/enabled
swapon /dev/zram0 # zram0 is a 48G swap device
mkdir -p /sys/fs/cgroup/memory/test
echo 1G > /sys/fs/cgroup/test/memory.max
echo $BASHPID > /sys/fs/cgroup/test/cgroup.procs
while true; do
    dd if=/dev/zero of=/tmp/test.img bs=1M count=5120
    cat /tmp/test.img > /dev/null
    rm /tmp/test.img
done

Then after a while:
watchdog: BUG: soft lockup - CPU#0 stuck for 763s! [cat:5787]
Modules linked in: zram virtiofs
CPU: 0 UID: 0 PID: 5787 Comm: cat Kdump: loaded Tainted: G             L      6.15.0.orig-gf3021d9246bc-dirty #118 PREEMPT(voluntary)·
Tainted: [L]=SOFTLOCKUP
Hardware name: Red Hat KVM/RHEL-AV, BIOS 0.0.0 02/06/2015
RIP: 0010:mpol_shared_policy_lookup+0xd/0x70
Code: e9 b8 b4 ff ff 31 c0 c3 cc cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 66 0f 1f 00 0f 1f 44 00 00 41 54 55 53 <48> 8b 1f 48 85 db 74 41 4c 8d 67 08 48 89 fb 48 89 f5 4c 89 e7 e8
RSP: 0018:ffffc90002b1fc28 EFLAGS: 00000202
RAX: 00000000001c20ca RBX: 0000000000724e1e RCX: 0000000000000001
RDX: ffff888118e214c8 RSI: 0000000000057d42 RDI: ffff888118e21518
RBP: 000000000002bec8 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000bf4 R11: 0000000000000000 R12: 0000000000000001
R13: 00000000001c20ca R14: 00000000001c20ca R15: 0000000000000000
FS:  00007f03f995c740(0000) GS:ffff88a07ad9a000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f03f98f1000 CR3: 0000000144626004 CR4: 0000000000770eb0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
PKRU: 55555554
Call Trace:
 <TASK>
 shmem_alloc_folio+0x31/0xc0
 shmem_swapin_folio+0x309/0xcf0
 ? filemap_get_entry+0x117/0x1e0
 ? xas_load+0xd/0xb0
 ? filemap_get_entry+0x101/0x1e0
 shmem_get_folio_gfp+0x2ed/0x5b0
 shmem_file_read_iter+0x7f/0x2e0
 vfs_read+0x252/0x330
 ksys_read+0x68/0xf0
 do_syscall_64+0x4c/0x1c0
 entry_SYSCALL_64_after_hwframe+0x76/0x7e
RIP: 0033:0x7f03f9a46991
Code: 00 48 8b 15 81 14 10 00 f7 d8 64 89 02 b8 ff ff ff ff eb bd e8 20 ad 01 00 f3 0f 1e fa 80 3d 35 97 10 00 00 74 13 31 c0 0f 05 <48> 3d 00 f0 ff ff 77 4f c3 66 0f 1f 44 00 00 55 48 89 e5 48 83 ec
RSP: 002b:00007fff3c52bd28 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 0000000000040000 RCX: 00007f03f9a46991
RDX: 0000000000040000 RSI: 00007f03f98ba000 RDI: 0000000000000003
RBP: 00007fff3c52bd50 R08: 0000000000000000 R09: 00007f03f9b9a380
R10: 0000000000000022 R11: 0000000000000246 R12: 0000000000040000
R13: 00007f03f98ba000 R14: 0000000000000003 R15: 0000000000000000
 </TASK>

The reason is simple, readahead brought some order 0 folio in swap cache,
and the swapin mTHP folio being allocated is in conflict with it, so
swapcache_prepare fails and causes shmem_swap_alloc_folio to return
-EEXIST, and shmem simply retries again and again causing this loop.

Fix it by applying a similar fix for anon mTHP swapin.

The performance change is very slight, time of swapin 10g zero folios
with shmem (test for 12 times):
Before:  2.47s
After:   2.48s

[kasong@tencent.com: add comment]
  Link: https://lkml.kernel.org/r/20250610181645.45922-1-ryncsn@gmail.com
Link: https://lkml.kernel.org/r/20250610181645.45922-1-ryncsn@gmail.com
Link: https://lkml.kernel.org/r/20250609171751.36305-1-ryncsn@gmail.com
Fixes: 1dd44c0af4 ("mm: shmem: skip swapcache for swapin of synchronous swap device")
Signed-off-by: Kairui Song <kasong@tencent.com>
Reviewed-by: Barry Song <baohua@kernel.org>
Acked-by: Nhat Pham <nphamcs@gmail.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: Usama Arif <usamaarif642@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2025-06-19 20:48:01 -07:00
Linus Torvalds
00c010e130 - The 11 patch series "Add folio_mk_pte()" from Matthew Wilcox 
simplifies the act of creating a pte which addresses the first page in a
   folio and reduces the amount of plumbing which architecture must
   implement to provide this.
 
 - The 8 patch series "Misc folio patches for 6.16" from Matthew Wilcox
   is a shower of largely unrelated folio infrastructure changes which
   clean things up and better prepare us for future work.
 
 - The 3 patch series "memory,x86,acpi: hotplug memory alignment
   advisement" from Gregory Price adds early-init code to prevent x86 from
   leaving physical memory unused when physical address regions are not
   aligned to memory block size.
 
 - The 2 patch series "mm/compaction: allow more aggressive proactive
   compaction" from Michal Clapinski provides some tuning of the (sadly,
   hard-coded (more sadly, not auto-tuned)) thresholds for our invokation
   of proactive compaction.  In a simple test case, the reduction of a guest
   VM's memory consumption was dramatic.
 
 - The 8 patch series "Minor cleanups and improvements to swap freeing
   code" from Kemeng Shi provides some code cleaups and a small efficiency
   improvement to this part of our swap handling code.
 
 - The 6 patch series "ptrace: introduce PTRACE_SET_SYSCALL_INFO API"
   from Dmitry Levin adds the ability for a ptracer to modify syscalls
   arguments.  At this time we can alter only "system call information that
   are used by strace system call tampering, namely, syscall number,
   syscall arguments, and syscall return value.
 
   This series should have been incorporated into mm.git's "non-MM"
   branch, but I goofed.
 
 - The 3 patch series "fs/proc: extend the PAGEMAP_SCAN ioctl to report
   guard regions" from Andrei Vagin extends the info returned by the
   PAGEMAP_SCAN ioctl against /proc/pid/pagemap.  This permits CRIU to more
   efficiently get at the info about guard regions.
 
 - The 2 patch series "Fix parameter passed to page_mapcount_is_type()"
   from Gavin Shan implements that fix.  No runtime effect is expected
   because validate_page_before_insert() happens to fix up this error.
 
 - The 3 patch series "kernel/events/uprobes: uprobe_write_opcode()
   rewrite" from David Hildenbrand basically brings uprobe text poking into
   the current decade.  Remove a bunch of hand-rolled implementation in
   favor of using more current facilities.
 
 - The 3 patch series "mm/ptdump: Drop assumption that pxd_val() is u64"
   from Anshuman Khandual provides enhancements and generalizations to the
   pte dumping code.  This might be needed when 128-bit Page Table
   Descriptors are enabled for ARM.
 
 - The 12 patch series "Always call constructor for kernel page tables"
   from Kevin Brodsky "ensures that the ctor/dtor is always called for
   kernel pgtables, as it already is for user pgtables".  This permits the
   addition of more functionality such as "insert hooks to protect page
   tables".  This change does result in various architectures performing
   unnecesary work, but this is fixed up where it is anticipated to occur.
 
 - The 9 patch series "Rust support for mm_struct, vm_area_struct, and
   mmap" from Alice Ryhl adds plumbing to permit Rust access to core MM
   structures.
 
 - The 3 patch series "fix incorrectly disallowed anonymous VMA merges"
   from Lorenzo Stoakes takes advantage of some VMA merging opportunities
   which we've been missing for 15 years.
 
 - The 4 patch series "mm/madvise: batch tlb flushes for MADV_DONTNEED
   and MADV_FREE" from SeongJae Park optimizes process_madvise()'s TLB
   flushing.  Instead of flushing each address range in the provided iovec,
   we batch the flushing across all the iovec entries.  The syscall's cost
   was approximately halved with a microbenchmark which was designed to
   load this particular operation.
 
 - The 6 patch series "Track node vacancy to reduce worst case allocation
   counts" from Sidhartha Kumar makes the maple tree smarter about its node
   preallocation.  stress-ng mmap performance increased by single-digit
   percentages and the amount of unnecessarily preallocated memory was
   dramaticelly reduced.
 
 - The 3 patch series "mm/gup: Minor fix, cleanup and improvements" from
   Baoquan He removes a few unnecessary things which Baoquan noted when
   reading the code.
 
 - The 3 patch series ""Enhance sysfs handling for memory hotplug in
   weighted interleave" from Rakie Kim "enhances the weighted interleave
   policy in the memory management subsystem by improving sysfs handling,
   fixing memory leaks, and introducing dynamic sysfs updates for memory
   hotplug support".  Fixes things on error paths which we are unlikely to
   hit.
 
 - The 7 patch series "mm/damon: auto-tune DAMOS for NUMA setups
   including tiered memory" from SeongJae Park introduces new DAMOS quota
   goal metrics which eliminate the manual tuning which is required when
   utilizing DAMON for memory tiering.
 
 - The 5 patch series "mm/vmalloc.c: code cleanup and improvements" from
   Baoquan He provides cleanups and small efficiency improvements which
   Baoquan found via code inspection.
 
 - The 2 patch series "vmscan: enforce mems_effective during demotion"
   from Gregory Price "changes reclaim to respect cpuset.mems_effective
   during demotion when possible".  because "presently, reclaim explicitly
   ignores cpuset.mems_effective when demoting, which may cause the cpuset
   settings to violated." "This is useful for isolating workloads on a
   multi-tenant system from certain classes of memory more consistently."
 
 - The 2 patch series ""Clean up split_huge_pmd_locked() and remove
   unnecessary folio pointers" from Gavin Guo provides minor cleanups and
   efficiency gains in in the huge page splitting and migrating code.
 
 - The 3 patch series "Use kmem_cache for memcg alloc" from Huan Yang
   creates a slab cache for `struct mem_cgroup', yielding improved memory
   utilization.
 
 - The 4 patch series "add max arg to swappiness in memory.reclaim and
   lru_gen" from Zhongkun He adds a new "max" argument to the "swappiness="
   argument for memory.reclaim MGLRU's lru_gen.  This directs proactive
   reclaim to reclaim from only anon folios rather than file-backed folios.
 
 - The 17 patch series "kexec: introduce Kexec HandOver (KHO)" from Mike
   Rapoport is the first step on the path to permitting the kernel to
   maintain existing VMs while replacing the host kernel via file-based
   kexec.  At this time only memblock's reserve_mem is preserved.
 
 - The 7 patch series "mm: Introduce for_each_valid_pfn()" from David
   Woodhouse provides and uses a smarter way of looping over a pfn range.
   By skipping ranges of invalid pfns.
 
 - The 2 patch series "sched/numa: Skip VMA scanning on memory pinned to
   one NUMA node via cpuset.mems" from Libo Chen removes a lot of pointless
   VMA scanning when a task is pinned a single NUMA mode.  Dramatic
   performance benefits were seen in some real world cases.
 
 - The 2 patch series "JFS: Implement migrate_folio for
   jfs_metapage_aops" from Shivank Garg addresses a warning which occurs
   during memory compaction when using JFS.
 
 - The 4 patch series "move all VMA allocation, freeing and duplication
   logic to mm" from Lorenzo Stoakes moves some VMA code from kernel/fork.c
   into the more appropriate mm/vma.c.
 
 - The 6 patch series "mm, swap: clean up swap cache mapping helper" from
   Kairui Song provides code consolidation and cleanups related to the
   folio_index() function.
 
 - The 2 patch series "mm/gup: Cleanup memfd_pin_folios()" from Vishal
   Moola does that.
 
 - The 8 patch series "memcg: Fix test_memcg_min/low test failures" from
   Waiman Long addresses some bogus failures which are being reported by
   the test_memcontrol selftest.
 
 - The 3 patch series "eliminate mmap() retry merge, add .mmap_prepare
   hook" from Lorenzo Stoakes commences the deprecation of
   file_operations.mmap() in favor of the new
   file_operations.mmap_prepare().  The latter is more restrictive and
   prevents drivers from messing with things in ways which, amongst other
   problems, may defeat VMA merging.
 
 - The 4 patch series "memcg: decouple memcg and objcg stocks"" from
   Shakeel Butt decouples the per-cpu memcg charge cache from the objcg's
   one.  This is a step along the way to making memcg and objcg charging
   NMI-safe, which is a BPF requirement.
 
 - The 6 patch series "mm/damon: minor fixups and improvements for code,
   tests, and documents" from SeongJae Park is "yet another batch of
   miscellaneous DAMON changes.  Fix and improve minor problems in code,
   tests and documents."
 
 - The 7 patch series "memcg: make memcg stats irq safe" from Shakeel
   Butt converts memcg stats to be irq safe.  Another step along the way to
   making memcg charging and stats updates NMI-safe, a BPF requirement.
 
 - The 4 patch series "Let unmap_hugepage_range() and several related
   functions take folio instead of page" from Fan Ni provides folio
   conversions in the hugetlb code.
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Merge tag 'mm-stable-2025-05-31-14-50' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Pull MM updates from Andrew Morton:

 - "Add folio_mk_pte()" from Matthew Wilcox simplifies the act of
   creating a pte which addresses the first page in a folio and reduces
   the amount of plumbing which architecture must implement to provide
   this.

 - "Misc folio patches for 6.16" from Matthew Wilcox is a shower of
   largely unrelated folio infrastructure changes which clean things up
   and better prepare us for future work.

 - "memory,x86,acpi: hotplug memory alignment advisement" from Gregory
   Price adds early-init code to prevent x86 from leaving physical
   memory unused when physical address regions are not aligned to memory
   block size.

 - "mm/compaction: allow more aggressive proactive compaction" from
   Michal Clapinski provides some tuning of the (sadly, hard-coded (more
   sadly, not auto-tuned)) thresholds for our invokation of proactive
   compaction. In a simple test case, the reduction of a guest VM's
   memory consumption was dramatic.

 - "Minor cleanups and improvements to swap freeing code" from Kemeng
   Shi provides some code cleaups and a small efficiency improvement to
   this part of our swap handling code.

 - "ptrace: introduce PTRACE_SET_SYSCALL_INFO API" from Dmitry Levin
   adds the ability for a ptracer to modify syscalls arguments. At this
   time we can alter only "system call information that are used by
   strace system call tampering, namely, syscall number, syscall
   arguments, and syscall return value.

   This series should have been incorporated into mm.git's "non-MM"
   branch, but I goofed.

 - "fs/proc: extend the PAGEMAP_SCAN ioctl to report guard regions" from
   Andrei Vagin extends the info returned by the PAGEMAP_SCAN ioctl
   against /proc/pid/pagemap. This permits CRIU to more efficiently get
   at the info about guard regions.

 - "Fix parameter passed to page_mapcount_is_type()" from Gavin Shan
   implements that fix. No runtime effect is expected because
   validate_page_before_insert() happens to fix up this error.

 - "kernel/events/uprobes: uprobe_write_opcode() rewrite" from David
   Hildenbrand basically brings uprobe text poking into the current
   decade. Remove a bunch of hand-rolled implementation in favor of
   using more current facilities.

 - "mm/ptdump: Drop assumption that pxd_val() is u64" from Anshuman
   Khandual provides enhancements and generalizations to the pte dumping
   code. This might be needed when 128-bit Page Table Descriptors are
   enabled for ARM.

 - "Always call constructor for kernel page tables" from Kevin Brodsky
   ensures that the ctor/dtor is always called for kernel pgtables, as
   it already is for user pgtables.

   This permits the addition of more functionality such as "insert hooks
   to protect page tables". This change does result in various
   architectures performing unnecesary work, but this is fixed up where
   it is anticipated to occur.

 - "Rust support for mm_struct, vm_area_struct, and mmap" from Alice
   Ryhl adds plumbing to permit Rust access to core MM structures.

 - "fix incorrectly disallowed anonymous VMA merges" from Lorenzo
   Stoakes takes advantage of some VMA merging opportunities which we've
   been missing for 15 years.

 - "mm/madvise: batch tlb flushes for MADV_DONTNEED and MADV_FREE" from
   SeongJae Park optimizes process_madvise()'s TLB flushing.

   Instead of flushing each address range in the provided iovec, we
   batch the flushing across all the iovec entries. The syscall's cost
   was approximately halved with a microbenchmark which was designed to
   load this particular operation.

 - "Track node vacancy to reduce worst case allocation counts" from
   Sidhartha Kumar makes the maple tree smarter about its node
   preallocation.

   stress-ng mmap performance increased by single-digit percentages and
   the amount of unnecessarily preallocated memory was dramaticelly
   reduced.

 - "mm/gup: Minor fix, cleanup and improvements" from Baoquan He removes
   a few unnecessary things which Baoquan noted when reading the code.

 - ""Enhance sysfs handling for memory hotplug in weighted interleave"
   from Rakie Kim "enhances the weighted interleave policy in the memory
   management subsystem by improving sysfs handling, fixing memory
   leaks, and introducing dynamic sysfs updates for memory hotplug
   support". Fixes things on error paths which we are unlikely to hit.

 - "mm/damon: auto-tune DAMOS for NUMA setups including tiered memory"
   from SeongJae Park introduces new DAMOS quota goal metrics which
   eliminate the manual tuning which is required when utilizing DAMON
   for memory tiering.

 - "mm/vmalloc.c: code cleanup and improvements" from Baoquan He
   provides cleanups and small efficiency improvements which Baoquan
   found via code inspection.

 - "vmscan: enforce mems_effective during demotion" from Gregory Price
   changes reclaim to respect cpuset.mems_effective during demotion when
   possible. because presently, reclaim explicitly ignores
   cpuset.mems_effective when demoting, which may cause the cpuset
   settings to violated.

   This is useful for isolating workloads on a multi-tenant system from
   certain classes of memory more consistently.

 - "Clean up split_huge_pmd_locked() and remove unnecessary folio
   pointers" from Gavin Guo provides minor cleanups and efficiency gains
   in in the huge page splitting and migrating code.

 - "Use kmem_cache for memcg alloc" from Huan Yang creates a slab cache
   for `struct mem_cgroup', yielding improved memory utilization.

 - "add max arg to swappiness in memory.reclaim and lru_gen" from
   Zhongkun He adds a new "max" argument to the "swappiness=" argument
   for memory.reclaim MGLRU's lru_gen.

   This directs proactive reclaim to reclaim from only anon folios
   rather than file-backed folios.

 - "kexec: introduce Kexec HandOver (KHO)" from Mike Rapoport is the
   first step on the path to permitting the kernel to maintain existing
   VMs while replacing the host kernel via file-based kexec. At this
   time only memblock's reserve_mem is preserved.

 - "mm: Introduce for_each_valid_pfn()" from David Woodhouse provides
   and uses a smarter way of looping over a pfn range. By skipping
   ranges of invalid pfns.

 - "sched/numa: Skip VMA scanning on memory pinned to one NUMA node via
   cpuset.mems" from Libo Chen removes a lot of pointless VMA scanning
   when a task is pinned a single NUMA mode.

   Dramatic performance benefits were seen in some real world cases.

 - "JFS: Implement migrate_folio for jfs_metapage_aops" from Shivank
   Garg addresses a warning which occurs during memory compaction when
   using JFS.

 - "move all VMA allocation, freeing and duplication logic to mm" from
   Lorenzo Stoakes moves some VMA code from kernel/fork.c into the more
   appropriate mm/vma.c.

 - "mm, swap: clean up swap cache mapping helper" from Kairui Song
   provides code consolidation and cleanups related to the folio_index()
   function.

 - "mm/gup: Cleanup memfd_pin_folios()" from Vishal Moola does that.

 - "memcg: Fix test_memcg_min/low test failures" from Waiman Long
   addresses some bogus failures which are being reported by the
   test_memcontrol selftest.

 - "eliminate mmap() retry merge, add .mmap_prepare hook" from Lorenzo
   Stoakes commences the deprecation of file_operations.mmap() in favor
   of the new file_operations.mmap_prepare().

   The latter is more restrictive and prevents drivers from messing with
   things in ways which, amongst other problems, may defeat VMA merging.

 - "memcg: decouple memcg and objcg stocks"" from Shakeel Butt decouples
   the per-cpu memcg charge cache from the objcg's one.

   This is a step along the way to making memcg and objcg charging
   NMI-safe, which is a BPF requirement.

 - "mm/damon: minor fixups and improvements for code, tests, and
   documents" from SeongJae Park is yet another batch of miscellaneous
   DAMON changes. Fix and improve minor problems in code, tests and
   documents.

 - "memcg: make memcg stats irq safe" from Shakeel Butt converts memcg
   stats to be irq safe. Another step along the way to making memcg
   charging and stats updates NMI-safe, a BPF requirement.

 - "Let unmap_hugepage_range() and several related functions take folio
   instead of page" from Fan Ni provides folio conversions in the
   hugetlb code.

* tag 'mm-stable-2025-05-31-14-50' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (285 commits)
  mm: pcp: increase pcp->free_count threshold to trigger free_high
  mm/hugetlb: convert use of struct page to folio in __unmap_hugepage_range()
  mm/hugetlb: refactor __unmap_hugepage_range() to take folio instead of page
  mm/hugetlb: refactor unmap_hugepage_range() to take folio instead of page
  mm/hugetlb: pass folio instead of page to unmap_ref_private()
  memcg: objcg stock trylock without irq disabling
  memcg: no stock lock for cpu hot-unplug
  memcg: make __mod_memcg_lruvec_state re-entrant safe against irqs
  memcg: make count_memcg_events re-entrant safe against irqs
  memcg: make mod_memcg_state re-entrant safe against irqs
  memcg: move preempt disable to callers of memcg_rstat_updated
  memcg: memcg_rstat_updated re-entrant safe against irqs
  mm: khugepaged: decouple SHMEM and file folios' collapse
  selftests/eventfd: correct test name and improve messages
  alloc_tag: check mem_profiling_support in alloc_tag_init
  Docs/damon: update titles and brief introductions to explain DAMOS
  selftests/damon/_damon_sysfs: read tried regions directories in order
  mm/damon/tests/core-kunit: add a test for damos_set_filters_default_reject()
  mm/damon/paddr: remove unused variable, folio_list, in damon_pa_stat()
  mm/damon/sysfs-schemes: fix wrong comment on damons_sysfs_quota_goal_metric_strs
  ...
 2025-05-31 15:44:16 -07:00
Kairui Song
7d0f0f0615 mm: move folio_index to mm/swap.h and remove no longer needed helper 
There are no remaining users of folio_index() outside the mm subsystem. 
Move it to mm/swap.h to co-locate it with swap_cache_index(), eliminating
a forward declaration, and a function call overhead.

Also remove the helper that was used to fix circular header dependency
issue.

Link: https://lkml.kernel.org/r/20250430181052.55698-6-ryncsn@gmail.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Chao Yu <chao@kernel.org>
Cc: Chris Li <chrisl@kernel.org>
Cc: Chris Mason <clm@fb.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Sterba <dsterba@suse.com>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: Joanne Koong <joannelkoong@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Qu Wenruo <wqu@suse.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2025-05-12 23:50:50 -07:00
Matthew Wilcox (Oracle)
84798514db
mm: Remove swap_writepage() and shmem_writepage() 
Call swap_writeout() and shmem_writeout() from pageout() instead.

Signed-off-by: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Link: https://lore.kernel.org/r/20250402150005.2309458-9-willy@infradead.org
Tested-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
 2025-04-07 09:36:50 +02:00
Linus Torvalds
eb0ece1602 - The 6 patch series "Enable strict percpu address space checks" from 
Uros Bizjak uses x86 named address space qualifiers to provide
   compile-time checking of percpu area accesses.
 
   This has caused a small amount of fallout - two or three issues were
   reported.  In all cases the calling code was founf to be incorrect.
 
 - The 4 patch series "Some cleanup for memcg" from Chen Ridong
   implements some relatively monir cleanups for the memcontrol code.
 
 - The 17 patch series "mm: fixes for device-exclusive entries (hmm)"
   from David Hildenbrand fixes a boatload of issues which David found then
   using device-exclusive PTE entries when THP is enabled.  More work is
   needed, but this makes thins better - our own HMM selftests now succeed.
 
 - The 2 patch series "mm: zswap: remove z3fold and zbud" from Yosry
   Ahmed remove the z3fold and zbud implementations.  They have been
   deprecated for half a year and nobody has complained.
 
 - The 5 patch series "mm: further simplify VMA merge operation" from
   Lorenzo Stoakes implements numerous simplifications in this area.  No
   runtime effects are anticipated.
 
 - The 4 patch series "mm/madvise: remove redundant mmap_lock operations
   from process_madvise()" from SeongJae Park rationalizes the locking in
   the madvise() implementation.  Performance gains of 20-25% were observed
   in one MADV_DONTNEED microbenchmark.
 
 - The 12 patch series "Tiny cleanup and improvements about SWAP code"
   from Baoquan He contains a number of touchups to issues which Baoquan
   noticed when working on the swap code.
 
 - The 2 patch series "mm: kmemleak: Usability improvements" from Catalin
   Marinas implements a couple of improvements to the kmemleak user-visible
   output.
 
 - The 2 patch series "mm/damon/paddr: fix large folios access and
   schemes handling" from Usama Arif provides a couple of fixes for DAMON's
   handling of large folios.
 
 - The 3 patch series "mm/damon/core: fix wrong and/or useless
   damos_walk() behaviors" from SeongJae Park fixes a few issues with the
   accuracy of kdamond's walking of DAMON regions.
 
 - The 3 patch series "expose mapping wrprotect, fix fb_defio use" from
   Lorenzo Stoakes changes the interaction between framebuffer deferred-io
   and core MM.  No functional changes are anticipated - this is
   preparatory work for the future removal of page structure fields.
 
 - The 4 patch series "mm/damon: add support for hugepage_size DAMOS
   filter" from Usama Arif adds a DAMOS filter which permits the filtering
   by huge page sizes.
 
 - The 4 patch series "mm: permit guard regions for file-backed/shmem
   mappings" from Lorenzo Stoakes extends the guard region feature from its
   present "anon mappings only" state.  The feature now covers shmem and
   file-backed mappings.
 
 - The 4 patch series "mm: batched unmap lazyfree large folios during
   reclamation" from Barry Song cleans up and speeds up the unmapping for
   pte-mapped large folios.
 
 - The 18 patch series "reimplement per-vma lock as a refcount" from
   Suren Baghdasaryan puts the vm_lock back into the vma.  Our reasons for
   pulling it out were largely bogus and that change made the code more
   messy.  This patchset provides small (0-10%) improvements on one
   microbenchmark.
 
 - The 5 patch series "Docs/mm/damon: misc DAMOS filters documentation
   fixes and improves" from SeongJae Park does some maintenance work on the
   DAMON docs.
 
 - The 27 patch series "hugetlb/CMA improvements for large systems" from
   Frank van der Linden addresses a pile of issues which have been observed
   when using CMA on large machines.
 
 - The 2 patch series "mm/damon: introduce DAMOS filter type for unmapped
   pages" from SeongJae Park enables users of DMAON/DAMOS to filter my the
   page's mapped/unmapped status.
 
 - The 19 patch series "zsmalloc/zram: there be preemption" from Sergey
   Senozhatsky teaches zram to run its compression and decompression
   operations preemptibly.
 
 - The 12 patch series "selftests/mm: Some cleanups from trying to run
   them" from Brendan Jackman fixes a pile of unrelated issues which
   Brendan encountered while runnimg our selftests.
 
 - The 2 patch series "fs/proc/task_mmu: add guard region bit to pagemap"
   from Lorenzo Stoakes permits userspace to use /proc/pid/pagemap to
   determine whether a particular page is a guard page.
 
 - The 7 patch series "mm, swap: remove swap slot cache" from Kairui Song
   removes the swap slot cache from the allocation path - it simply wasn't
   being effective.
 
 - The 5 patch series "mm: cleanups for device-exclusive entries (hmm)"
   from David Hildenbrand implements a number of unrelated cleanups in this
   code.
 
 - The 5 patch series "mm: Rework generic PTDUMP configs" from Anshuman
   Khandual implements a number of preparatoty cleanups to the
   GENERIC_PTDUMP Kconfig logic.
 
 - The 8 patch series "mm/damon: auto-tune aggregation interval" from
   SeongJae Park implements a feedback-driven automatic tuning feature for
   DAMON's aggregation interval tuning.
 
 - The 5 patch series "Fix lazy mmu mode" from Ryan Roberts fixes some
   issues in powerpc, sparc and x86 lazy MMU implementations.  Ryan did
   this in preparation for implementing lazy mmu mode for arm64 to optimize
   vmalloc.
 
 - The 2 patch series "mm/page_alloc: Some clarifications for migratetype
   fallback" from Brendan Jackman reworks some commentary to make the code
   easier to follow.
 
 - The 3 patch series "page_counter cleanup and size reduction" from
   Shakeel Butt cleans up the page_counter code and fixes a size increase
   which we accidentally added late last year.
 
 - The 3 patch series "Add a command line option that enables control of
   how many threads should be used to allocate huge pages" from Thomas
   Prescher does that.  It allows the careful operator to significantly
   reduce boot time by tuning the parallalization of huge page
   initialization.
 
 - The 3 patch series "Fix calculations in trace_balance_dirty_pages()
   for cgwb" from Tang Yizhou fixes the tracing output from the dirty page
   balancing code.
 
 - The 9 patch series "mm/damon: make allow filters after reject filters
   useful and intuitive" from SeongJae Park improves the handling of allow
   and reject filters.  Behaviour is made more consistent and the
   documention is updated accordingly.
 
 - The 5 patch series "Switch zswap to object read/write APIs" from Yosry
   Ahmed updates zswap to the new object read/write APIs and thus permits
   the removal of some legacy code from zpool and zsmalloc.
 
 - The 6 patch series "Some trivial cleanups for shmem" from Baolin Wang
   does as it claims.
 
 - The 20 patch series "fs/dax: Fix ZONE_DEVICE page reference counts"
   from Alistair Popple regularizes the weird ZONE_DEVICE page refcount
   handling in DAX, permittig the removal of a number of special-case
   checks.
 
 - The 4 patch series "refactor mremap and fix bug" from Lorenzo Stoakes
   is a preparatoty refactoring and cleanup of the mremap() code.
 
 - The 20 patch series "mm: MM owner tracking for large folios (!hugetlb)
   + CONFIG_NO_PAGE_MAPCOUNT" from David Hildenbrand reworks the manner in
   which we determine whether a large folio is known to be mapped
   exclusively into a single MM.
 
 - The 8 patch series "mm/damon: add sysfs dirs for managing DAMOS
   filters based on handling layers" from SeongJae Park adds a couple of
   new sysfs directories to ease the management of DAMON/DAMOS filters.
 
 - The 13 patch series "arch, mm: reduce code duplication in mem_init()"
   from Mike Rapoport consolidates many per-arch implementations of
   mem_init() into code generic code, where that is practical.
 
 - The 13 patch series "mm/damon/sysfs: commit parameters online via
   damon_call()" from SeongJae Park continues the cleaning up of sysfs
   access to DAMON internal data.
 
 - The 3 patch series "mm: page_ext: Introduce new iteration API" from
   Luiz Capitulino reworks the page_ext initialization to fix a boot-time
   crash which was observed with an unusual combination of compile and
   cmdline options.
 
 - The 8 patch series "Buddy allocator like (or non-uniform) folio split"
   from Zi Yan reworks the code to split a folio into smaller folios.  The
   main benefit is lessened memory consumption: fewer post-split folios are
   generated.
 
 - The 2 patch series "Minimize xa_node allocation during xarry split"
   from Zi Yan reduces the number of xarray xa_nodes which are generated
   during an xarray split.
 
 - The 2 patch series "drivers/base/memory: Two cleanups" from Gavin Shan
   performs some maintenance work on the drivers/base/memory code.
 
 - The 3 patch series "Add tracepoints for lowmem reserves, watermarks
   and totalreserve_pages" from Martin Liu adds some more tracepoints to
   the page allocator code.
 
 - The 4 patch series "mm/madvise: cleanup requests validations and
   classifications" from SeongJae Park cleans up some warts which SeongJae
   observed during his earlier madvise work.
 
 - The 3 patch series "mm/hwpoison: Fix regressions in memory failure
   handling" from Shuai Xue addresses two quite serious regressions which
   Shuai has observed in the memory-failure implementation.
 
 - The 5 patch series "mm: reliable huge page allocator" from Johannes
   Weiner makes huge page allocations cheaper and more reliable by reducing
   fragmentation.
 
 - The 5 patch series "Minor memcg cleanups & prep for memdescs" from
   Matthew Wilcox is preparatory work for the future implementation of
   memdescs.
 
 - The 4 patch series "track memory used by balloon drivers" from Nico
   Pache introduces a way to track memory used by our various balloon
   drivers.
 
 - The 2 patch series "mm/damon: introduce DAMOS filter type for active
   pages" from Nhat Pham permits users to filter for active/inactive pages,
   separately for file and anon pages.
 
 - The 2 patch series "Adding Proactive Memory Reclaim Statistics" from
   Hao Jia separates the proactive reclaim statistics from the direct
   reclaim statistics.
 
 - The 2 patch series "mm/vmscan: don't try to reclaim hwpoison folio"
   from Jinjiang Tu fixes our handling of hwpoisoned pages within the
   reclaim code.
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Merge tag 'mm-stable-2025-03-30-16-52' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Pull MM updates from Andrew Morton:

 - The series "Enable strict percpu address space checks" from Uros
   Bizjak uses x86 named address space qualifiers to provide
   compile-time checking of percpu area accesses.

   This has caused a small amount of fallout - two or three issues were
   reported. In all cases the calling code was found to be incorrect.

 - The series "Some cleanup for memcg" from Chen Ridong implements some
   relatively monir cleanups for the memcontrol code.

 - The series "mm: fixes for device-exclusive entries (hmm)" from David
   Hildenbrand fixes a boatload of issues which David found then using
   device-exclusive PTE entries when THP is enabled. More work is
   needed, but this makes thins better - our own HMM selftests now
   succeed.

 - The series "mm: zswap: remove z3fold and zbud" from Yosry Ahmed
   remove the z3fold and zbud implementations. They have been deprecated
   for half a year and nobody has complained.

 - The series "mm: further simplify VMA merge operation" from Lorenzo
   Stoakes implements numerous simplifications in this area. No runtime
   effects are anticipated.

 - The series "mm/madvise: remove redundant mmap_lock operations from
   process_madvise()" from SeongJae Park rationalizes the locking in the
   madvise() implementation. Performance gains of 20-25% were observed
   in one MADV_DONTNEED microbenchmark.

 - The series "Tiny cleanup and improvements about SWAP code" from
   Baoquan He contains a number of touchups to issues which Baoquan
   noticed when working on the swap code.

 - The series "mm: kmemleak: Usability improvements" from Catalin
   Marinas implements a couple of improvements to the kmemleak
   user-visible output.

 - The series "mm/damon/paddr: fix large folios access and schemes
   handling" from Usama Arif provides a couple of fixes for DAMON's
   handling of large folios.

 - The series "mm/damon/core: fix wrong and/or useless damos_walk()
   behaviors" from SeongJae Park fixes a few issues with the accuracy of
   kdamond's walking of DAMON regions.

 - The series "expose mapping wrprotect, fix fb_defio use" from Lorenzo
   Stoakes changes the interaction between framebuffer deferred-io and
   core MM. No functional changes are anticipated - this is preparatory
   work for the future removal of page structure fields.

 - The series "mm/damon: add support for hugepage_size DAMOS filter"
   from Usama Arif adds a DAMOS filter which permits the filtering by
   huge page sizes.

 - The series "mm: permit guard regions for file-backed/shmem mappings"
   from Lorenzo Stoakes extends the guard region feature from its
   present "anon mappings only" state. The feature now covers shmem and
   file-backed mappings.

 - The series "mm: batched unmap lazyfree large folios during
   reclamation" from Barry Song cleans up and speeds up the unmapping
   for pte-mapped large folios.

 - The series "reimplement per-vma lock as a refcount" from Suren
   Baghdasaryan puts the vm_lock back into the vma. Our reasons for
   pulling it out were largely bogus and that change made the code more
   messy. This patchset provides small (0-10%) improvements on one
   microbenchmark.

 - The series "Docs/mm/damon: misc DAMOS filters documentation fixes and
   improves" from SeongJae Park does some maintenance work on the DAMON
   docs.

 - The series "hugetlb/CMA improvements for large systems" from Frank
   van der Linden addresses a pile of issues which have been observed
   when using CMA on large machines.

 - The series "mm/damon: introduce DAMOS filter type for unmapped pages"
   from SeongJae Park enables users of DMAON/DAMOS to filter my the
   page's mapped/unmapped status.

 - The series "zsmalloc/zram: there be preemption" from Sergey
   Senozhatsky teaches zram to run its compression and decompression
   operations preemptibly.

 - The series "selftests/mm: Some cleanups from trying to run them" from
   Brendan Jackman fixes a pile of unrelated issues which Brendan
   encountered while runnimg our selftests.

 - The series "fs/proc/task_mmu: add guard region bit to pagemap" from
   Lorenzo Stoakes permits userspace to use /proc/pid/pagemap to
   determine whether a particular page is a guard page.

 - The series "mm, swap: remove swap slot cache" from Kairui Song
   removes the swap slot cache from the allocation path - it simply
   wasn't being effective.

 - The series "mm: cleanups for device-exclusive entries (hmm)" from
   David Hildenbrand implements a number of unrelated cleanups in this
   code.

 - The series "mm: Rework generic PTDUMP configs" from Anshuman Khandual
   implements a number of preparatoty cleanups to the GENERIC_PTDUMP
   Kconfig logic.

 - The series "mm/damon: auto-tune aggregation interval" from SeongJae
   Park implements a feedback-driven automatic tuning feature for
   DAMON's aggregation interval tuning.

 - The series "Fix lazy mmu mode" from Ryan Roberts fixes some issues in
   powerpc, sparc and x86 lazy MMU implementations. Ryan did this in
   preparation for implementing lazy mmu mode for arm64 to optimize
   vmalloc.

 - The series "mm/page_alloc: Some clarifications for migratetype
   fallback" from Brendan Jackman reworks some commentary to make the
   code easier to follow.

 - The series "page_counter cleanup and size reduction" from Shakeel
   Butt cleans up the page_counter code and fixes a size increase which
   we accidentally added late last year.

 - The series "Add a command line option that enables control of how
   many threads should be used to allocate huge pages" from Thomas
   Prescher does that. It allows the careful operator to significantly
   reduce boot time by tuning the parallalization of huge page
   initialization.

 - The series "Fix calculations in trace_balance_dirty_pages() for cgwb"
   from Tang Yizhou fixes the tracing output from the dirty page
   balancing code.

 - The series "mm/damon: make allow filters after reject filters useful
   and intuitive" from SeongJae Park improves the handling of allow and
   reject filters. Behaviour is made more consistent and the documention
   is updated accordingly.

 - The series "Switch zswap to object read/write APIs" from Yosry Ahmed
   updates zswap to the new object read/write APIs and thus permits the
   removal of some legacy code from zpool and zsmalloc.

 - The series "Some trivial cleanups for shmem" from Baolin Wang does as
   it claims.

 - The series "fs/dax: Fix ZONE_DEVICE page reference counts" from
   Alistair Popple regularizes the weird ZONE_DEVICE page refcount
   handling in DAX, permittig the removal of a number of special-case
   checks.

 - The series "refactor mremap and fix bug" from Lorenzo Stoakes is a
   preparatoty refactoring and cleanup of the mremap() code.

 - The series "mm: MM owner tracking for large folios (!hugetlb) +
   CONFIG_NO_PAGE_MAPCOUNT" from David Hildenbrand reworks the manner in
   which we determine whether a large folio is known to be mapped
   exclusively into a single MM.

 - The series "mm/damon: add sysfs dirs for managing DAMOS filters based
   on handling layers" from SeongJae Park adds a couple of new sysfs
   directories to ease the management of DAMON/DAMOS filters.

 - The series "arch, mm: reduce code duplication in mem_init()" from
   Mike Rapoport consolidates many per-arch implementations of
   mem_init() into code generic code, where that is practical.

 - The series "mm/damon/sysfs: commit parameters online via
   damon_call()" from SeongJae Park continues the cleaning up of sysfs
   access to DAMON internal data.

 - The series "mm: page_ext: Introduce new iteration API" from Luiz
   Capitulino reworks the page_ext initialization to fix a boot-time
   crash which was observed with an unusual combination of compile and
   cmdline options.

 - The series "Buddy allocator like (or non-uniform) folio split" from
   Zi Yan reworks the code to split a folio into smaller folios. The
   main benefit is lessened memory consumption: fewer post-split folios
   are generated.

 - The series "Minimize xa_node allocation during xarry split" from Zi
   Yan reduces the number of xarray xa_nodes which are generated during
   an xarray split.

 - The series "drivers/base/memory: Two cleanups" from Gavin Shan
   performs some maintenance work on the drivers/base/memory code.

 - The series "Add tracepoints for lowmem reserves, watermarks and
   totalreserve_pages" from Martin Liu adds some more tracepoints to the
   page allocator code.

 - The series "mm/madvise: cleanup requests validations and
   classifications" from SeongJae Park cleans up some warts which
   SeongJae observed during his earlier madvise work.

 - The series "mm/hwpoison: Fix regressions in memory failure handling"
   from Shuai Xue addresses two quite serious regressions which Shuai
   has observed in the memory-failure implementation.

 - The series "mm: reliable huge page allocator" from Johannes Weiner
   makes huge page allocations cheaper and more reliable by reducing
   fragmentation.

 - The series "Minor memcg cleanups & prep for memdescs" from Matthew
   Wilcox is preparatory work for the future implementation of memdescs.

 - The series "track memory used by balloon drivers" from Nico Pache
   introduces a way to track memory used by our various balloon drivers.

 - The series "mm/damon: introduce DAMOS filter type for active pages"
   from Nhat Pham permits users to filter for active/inactive pages,
   separately for file and anon pages.

 - The series "Adding Proactive Memory Reclaim Statistics" from Hao Jia
   separates the proactive reclaim statistics from the direct reclaim
   statistics.

 - The series "mm/vmscan: don't try to reclaim hwpoison folio" from
   Jinjiang Tu fixes our handling of hwpoisoned pages within the reclaim
   code.

* tag 'mm-stable-2025-03-30-16-52' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (431 commits)
  mm/page_alloc: remove unnecessary __maybe_unused in order_to_pindex()
  x86/mm: restore early initialization of high_memory for 32-bits
  mm/vmscan: don't try to reclaim hwpoison folio
  mm/hwpoison: introduce folio_contain_hwpoisoned_page() helper
  cgroup: docs: add pswpin and pswpout items in cgroup v2 doc
  mm: vmscan: split proactive reclaim statistics from direct reclaim statistics
  selftests/mm: speed up split_huge_page_test
  selftests/mm: uffd-unit-tests support for hugepages > 2M
  docs/mm/damon/design: document active DAMOS filter type
  mm/damon: implement a new DAMOS filter type for active pages
  fs/dax: don't disassociate zero page entries
  MM documentation: add "Unaccepted" meminfo entry
  selftests/mm: add commentary about 9pfs bugs
  fork: use __vmalloc_node() for stack allocation
  docs/mm: Physical Memory: Populate the "Zones" section
  xen: balloon: update the NR_BALLOON_PAGES state
  hv_balloon: update the NR_BALLOON_PAGES state
  balloon_compaction: update the NR_BALLOON_PAGES state
  meminfo: add a per node counter for balloon drivers
  mm: remove references to folio in __memcg_kmem_uncharge_page()
  ...
 2025-04-01 09:29:18 -07:00
Kairui Song
b487a2da35 mm, swap: simplify folio swap allocation 
With slot cache gone, clean up the allocation helpers even more. 
folio_alloc_swap will be the only entry for allocation and adding the
folio to swap cache (except suspend), making it opposite of
folio_free_swap.

Link: https://lkml.kernel.org/r/20250313165935.63303-8-ryncsn@gmail.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Barry Song <v-songbaohua@oppo.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kalesh Singh <kaleshsingh@google.com>
Cc: Matthew Wilcow (Oracle) <willy@infradead.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2025-03-16 22:06:44 -07:00
Kaixiong Yu
7e05627ee1 mm: swap: move sysctl to mm/swap.c 
The page-cluster belongs to mm/swap.c, move it to mm/swap.c .
Removes the redundant external variable declaration and unneeded
include(linux/swap.h).

Signed-off-by: Kaixiong Yu <yukaixiong@huawei.com>
Reviewed-by: Kees Cook <kees@kernel.org>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Joel Granados <joel.granados@kernel.org>
 2025-02-07 16:53:04 +01:00
Barry Song
9d57090e73 mm: fix swap_read_folio_zeromap() for large folios with partial zeromap 
Patch series "mm: enable large folios swap-in support", v9.

Currently, we support mTHP swapout but not swapin.  This means that once
mTHP is swapped out, it will come back as small folios when swapped in. 
This is particularly detrimental for devices like Android, where more than
half of the memory is in swap.

The lack of mTHP swapin functionality makes mTHP a showstopper in
scenarios that heavily rely on swap.  This patchset introduces mTHP
swap-in support.  It starts with synchronous devices similar to zRAM,
aiming to benefit as many users as possible with minimal changes.


This patch (of 3):

There could be a corner case where the first entry is non-zeromap, but a
subsequent entry is zeromap.  In this case, we should not let
swap_read_folio_zeromap() return false since we will still read corrupted
data.

Additionally, the iteration of test_bit() is unnecessary and can be
replaced with bitmap operations, which are more efficient.

We can adopt the style of swap_pte_batch() and folio_pte_batch() to
introduce swap_zeromap_batch() which seems to provide the greatest
flexibility for the caller.  This approach allows the caller to either
check if the zeromap status of all entries is consistent or determine the
number of contiguous entries with the same status.

Since swap_read_folio() can't handle reading a large folio that's
partially zeromap and partially non-zeromap, we've moved the code to
mm/swap.h so that others, like those working on swap-in, can access it.

Link: https://lkml.kernel.org/r/20240908232119.2157-1-21cnbao@gmail.com
Link: https://lkml.kernel.org/r/20240908232119.2157-2-21cnbao@gmail.com
Fixes: 0ca0c24e32 ("mm: store zero pages to be swapped out in a bitmap")
Signed-off-by: Barry Song <v-songbaohua@oppo.com>
Reviewed-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Usama Arif <usamaarif642@gmail.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Chuanhua Han <hanchuanhua@oppo.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Gao Xiang <xiang@kernel.org>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kairui Song <kasong@tencent.com>
Cc: Kairui Song <ryncsn@gmail.com>
Cc: Kalesh Singh <kaleshsingh@google.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Kanchana P Sridhar <kanchana.p.sridhar@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2024-09-17 01:07:01 -07:00
Matthew Wilcox (Oracle)
94dc8bffd8 mm: return the folio from swapin_readahead 
The unuse_pte_range() caller only wants the folio while do_swap_page()
wants both the page and the folio.  Since do_swap_page() already has logic
for handling both the folio and the page, move the folio-to-page logic
there.  This also lets us allocate larger folios in the SWP_SYNCHRONOUS_IO
path in future.

Link: https://lkml.kernel.org/r/20240807193734.1865400-1-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2024-09-01 20:26:05 -07:00
Barry Song
9f101bef40 mm: swap: add nr argument in swapcache_prepare and swapcache_clear to support large folios 
Right now, swapcache_prepare() and swapcache_clear() supports one entry
only, to support large folios, we need to handle multiple swap entries.

To optimize stack usage, we iterate twice in __swap_duplicate(): the first
time to verify that all entries are valid, and the second time to apply
the modifications to the entries.

Currently, we're using nr=1 for the existing users.

[v-songbaohua@oppo.com: clarify swap_count_continued and improve readability for  __swap_duplicate]
  Link: https://lkml.kernel.org/r/20240802071817.47081-1-21cnbao@gmail.com
Link: https://lkml.kernel.org/r/20240730071339.107447-2-21cnbao@gmail.com
Signed-off-by: Barry Song <v-songbaohua@oppo.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Acked-by: David Hildenbrand <david@redhat.com>
Tested-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: Gao Xiang <xiang@kernel.org>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kairui Song <kasong@tencent.com>
Cc: Kalesh Singh <kaleshsingh@google.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2024-09-01 20:25:56 -07:00
Yosry Ahmed
b2d1f38b52 mm: swap: remove 'synchronous' argument to swap_read_folio() 
Commit [1] introduced IO polling support duding swapin to reduce swap read
latency for block devices that can be polled.  However later commit [2]
removed polling support.  Commit [3] removed the remnants of polling
support from read_swap_cache_async() and __read_swap_cache_async(). 
However, it left behind some remnants in swap_read_folio(), the
'synchronous' argument.

swap_read_folio() reads the folio synchronously if synchronous=true or if
SWP_SYNCHRONOUS_IO is set in swap_info_struct.  The only caller that
passes synchronous=true is in do_swap_page() in the SWP_SYNCHRONOUS_IO
case.

Hence, the argument is redundant, it is only set to true when the swap
read would have been synchronous anyway. Remove it.

[1] Commit 23955622ff ("swap: add block io poll in swapin path")
[2] Commit 9650b453a3 ("block: ignore RWF_HIPRI hint for sync dio")
[3] Commit b243dcbf2f ("swap: remove remnants of polling from read_swap_cache_async")

Link: https://lkml.kernel.org/r/20240607045515.1836558-1-yosryahmed@google.com
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2024-07-03 19:30:06 -07:00
Kairui Song
7aad25b4b4 mm/swap: reduce swap cache search space 
Currently we use one swap_address_space for every 64M chunk to reduce lock
contention, this is like having a set of smaller swap files inside one
swap device.  But when doing swap cache look up or insert, we are still
using the offset of the whole large swap device.  This is OK for
correctness, as the offset (key) is unique.

But Xarray is specially optimized for small indexes, it creates the radix
tree levels lazily to be just enough to fit the largest key stored in one
Xarray.  So we are wasting tree nodes unnecessarily.

For 64M chunk it should only take at most 3 levels to contain everything. 
But if we are using the offset from the whole swap device, the offset
(key) value will be way beyond 64M, and so will the tree level.

Optimize this by using a new helper swap_cache_index to get a swap entry's
unique offset in its own 64M swap_address_space.

I see a ~1% performance gain in benchmark and actual workload with high
memory pressure.

Test with `time memhog 128G` inside a 8G memcg using 128G swap (ramdisk
with SWP_SYNCHRONOUS_IO dropped, tested 3 times, results are stable.  The
test result is similar but the improvement is smaller if
SWP_SYNCHRONOUS_IO is enabled, as swap out path can never skip swap
cache):

Before:
6.07user 250.74system 4:17.26elapsed 99%CPU (0avgtext+0avgdata 8373376maxresident)k
0inputs+0outputs (55major+33555018minor)pagefaults 0swaps

After (1.8% faster):
6.08user 246.09system 4:12.58elapsed 99%CPU (0avgtext+0avgdata 8373248maxresident)k
0inputs+0outputs (54major+33555027minor)pagefaults 0swaps

Similar result with MySQL and sysbench using swap:
Before:
94055.61 qps

After (0.8% faster):
94834.91 qps

Radix tree slab usage is also very slightly lower.

Link: https://lkml.kernel.org/r/20240521175854.96038-12-ryncsn@gmail.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
Cc: Anna Schumaker <anna@kernel.org>
Cc: Barry Song <v-songbaohua@oppo.com>
Cc: Chao Yu <chao@kernel.org>
Cc: Chris Li <chrisl@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Ilya Dryomov <idryomov@gmail.com>
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: Jeff Layton <jlayton@kernel.org>
Cc: Marc Dionne <marc.dionne@auristor.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: NeilBrown <neilb@suse.de>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: Xiubo Li <xiubli@redhat.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2024-07-03 19:29:56 -07:00
Kairui Song
545ebe71d3 mm/swap: get the swap device offset directly 
folio_file_pos and page_file_offset are for mixed usage of swap cache and
page cache, it can't be page cache here, so introduce a new helper to get
the swap offset in swap device directly.

Need to include swapops.h in mm/swap.h to ensure swp_offset is always
defined before use.

Link: https://lkml.kernel.org/r/20240521175854.96038-9-ryncsn@gmail.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
Cc: Anna Schumaker <anna@kernel.org>
Cc: Barry Song <v-songbaohua@oppo.com>
Cc: Chao Yu <chao@kernel.org>
Cc: Chris Li <chrisl@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Ilya Dryomov <idryomov@gmail.com>
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: Jeff Layton <jlayton@kernel.org>
Cc: Marc Dionne <marc.dionne@auristor.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: NeilBrown <neilb@suse.de>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: Xiubo Li <xiubli@redhat.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2024-07-03 19:29:55 -07:00
Kairui Song
13ddaf26be mm/swap: fix race when skipping swapcache 
When skipping swapcache for SWP_SYNCHRONOUS_IO, if two or more threads
swapin the same entry at the same time, they get different pages (A, B). 
Before one thread (T0) finishes the swapin and installs page (A) to the
PTE, another thread (T1) could finish swapin of page (B), swap_free the
entry, then swap out the possibly modified page reusing the same entry. 
It breaks the pte_same check in (T0) because PTE value is unchanged,
causing ABA problem.  Thread (T0) will install a stalled page (A) into the
PTE and cause data corruption.

One possible callstack is like this:

CPU0                                 CPU1
----                                 ----
do_swap_page()                       do_swap_page() with same entry
<direct swapin path>                 <direct swapin path>
<alloc page A>                       <alloc page B>
swap_read_folio() <- read to page A  swap_read_folio() <- read to page B
<slow on later locks or interrupt>   <finished swapin first>
...                                  set_pte_at()
                                     swap_free() <- entry is free
                                     <write to page B, now page A stalled>
                                     <swap out page B to same swap entry>
pte_same() <- Check pass, PTE seems
              unchanged, but page A
              is stalled!
swap_free() <- page B content lost!
set_pte_at() <- staled page A installed!

And besides, for ZRAM, swap_free() allows the swap device to discard the
entry content, so even if page (B) is not modified, if swap_read_folio()
on CPU0 happens later than swap_free() on CPU1, it may also cause data
loss.

To fix this, reuse swapcache_prepare which will pin the swap entry using
the cache flag, and allow only one thread to swap it in, also prevent any
parallel code from putting the entry in the cache.  Release the pin after
PT unlocked.

Racers just loop and wait since it's a rare and very short event.  A
schedule_timeout_uninterruptible(1) call is added to avoid repeated page
faults wasting too much CPU, causing livelock or adding too much noise to
perf statistics.  A similar livelock issue was described in commit
029c4628b2 ("mm: swap: get rid of livelock in swapin readahead")

Reproducer:

This race issue can be triggered easily using a well constructed
reproducer and patched brd (with a delay in read path) [1]:

With latest 6.8 mainline, race caused data loss can be observed easily:
$ gcc -g -lpthread test-thread-swap-race.c && ./a.out
  Polulating 32MB of memory region...
  Keep swapping out...
  Starting round 0...
  Spawning 65536 workers...
  32746 workers spawned, wait for done...
  Round 0: Error on 0x5aa00, expected 32746, got 32743, 3 data loss!
  Round 0: Error on 0x395200, expected 32746, got 32743, 3 data loss!
  Round 0: Error on 0x3fd000, expected 32746, got 32737, 9 data loss!
  Round 0 Failed, 15 data loss!

This reproducer spawns multiple threads sharing the same memory region
using a small swap device.  Every two threads updates mapped pages one by
one in opposite direction trying to create a race, with one dedicated
thread keep swapping out the data out using madvise.

The reproducer created a reproduce rate of about once every 5 minutes, so
the race should be totally possible in production.

After this patch, I ran the reproducer for over a few hundred rounds and
no data loss observed.

Performance overhead is minimal, microbenchmark swapin 10G from 32G
zram:

Before:     10934698 us
After:      11157121 us
Cached:     13155355 us (Dropping SWP_SYNCHRONOUS_IO flag)

[kasong@tencent.com: v4]
  Link: https://lkml.kernel.org/r/20240219082040.7495-1-ryncsn@gmail.com
Link: https://lkml.kernel.org/r/20240206182559.32264-1-ryncsn@gmail.com
Fixes: 0bcac06f27 ("mm, swap: skip swapcache for swapin of synchronous device")
Reported-by: "Huang, Ying" <ying.huang@intel.com>
Closes: https://lore.kernel.org/lkml/87bk92gqpx.fsf_-_@yhuang6-desk2.ccr.corp.intel.com/
Link: https://github.com/ryncsn/emm-test-project/tree/master/swap-stress-race [1]
Signed-off-by: Kairui Song <kasong@tencent.com>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
Acked-by: Yu Zhao <yuzhao@google.com>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Chris Li <chrisl@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Yosry Ahmed <yosryahmed@google.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Barry Song <21cnbao@gmail.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2024-02-20 14:20:48 -08:00
Matthew Wilcox (Oracle)
a4575c4138 mm: convert swap_cluster_readahead and swap_vma_readahead to return a folio 
shmem_swapin_cluster() immediately converts the page back to a folio, and
swapin_readahead() may as well call folio_file_page() once instead of
having each function call it.

[willy@infradead.org: avoid NULL pointer deref]
  Link: https://lkml.kernel.org/r/ZYI7OcVlM1voKfBl@casper.infradead.org
Link: https://lkml.kernel.org/r/20231213215842.671461-14-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2023-12-29 11:58:32 -08:00
Matthew Wilcox (Oracle)
6e03492e9d mm: return a folio from read_swap_cache_async() 
The only two callers simply call put_page() on the page returned, so
they're happier calling folio_put().  Saves two calls to compound_head().

Link: https://lkml.kernel.org/r/20231213215842.671461-13-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2023-12-29 11:58:32 -08:00
Matthew Wilcox (Oracle)
69fe7d67cb mm: remove page_swap_info() 
It's more efficient to get the swap_info_struct by calling
swp_swap_info() directly.

Link: https://lkml.kernel.org/r/20231213215842.671461-12-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2023-12-29 11:58:32 -08:00
Matthew Wilcox (Oracle)
c9bdf768dd mm: convert swap_readpage() to swap_read_folio() 
All callers have a folio, so pass it in, saving two calls to
compound_head().

Link: https://lkml.kernel.org/r/20231213215842.671461-11-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2023-12-29 11:58:31 -08:00
Matthew Wilcox (Oracle)
b99b4e0d9d mm: pass a folio to __swap_writepage() 
Both callers now have a folio, so pass that in instead of the page. 
Removes a few hidden calls to compound_head().

Link: https://lkml.kernel.org/r/20231213215842.671461-3-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2023-12-29 11:58:29 -08:00
Matthew Wilcox (Oracle)
96c7b0b422 mm: return the folio from __read_swap_cache_async() 
Patch series "More swap folio conversions".

These all seem like fairly straightforward conversions to me.  A lot of
compound_head() calls get removed.  And page_swap_info(), which is nice.


This patch (of 13):

Move the folio->page conversion into the callers that actually want that. 
Most of the callers are happier with the folio anyway.  If the
page_allocated boolean is set, the folio allocated is of order-0, so it is
safe to pass the page directly to swap_readpage().

Link: https://lkml.kernel.org/r/20231213215842.671461-1-willy@infradead.org
Link: https://lkml.kernel.org/r/20231213215842.671461-2-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2023-12-29 11:58:29 -08:00
Domenico Cerasuolo
a65b0e7607 zswap: make shrinking memcg-aware 
Currently, we only have a single global LRU for zswap.  This makes it
impossible to perform worload-specific shrinking - an memcg cannot
determine which pages in the pool it owns, and often ends up writing pages
from other memcgs.  This issue has been previously observed in practice
and mitigated by simply disabling memcg-initiated shrinking:

https://lore.kernel.org/all/20230530232435.3097106-1-nphamcs@gmail.com/T/#u

This patch fully resolves the issue by replacing the global zswap LRU
with memcg- and NUMA-specific LRUs, and modify the reclaim logic:

a) When a store attempt hits an memcg limit, it now triggers a
   synchronous reclaim attempt that, if successful, allows the new
   hotter page to be accepted by zswap.
b) If the store attempt instead hits the global zswap limit, it will
   trigger an asynchronous reclaim attempt, in which an memcg is
   selected for reclaim in a round-robin-like fashion.

[nphamcs@gmail.com: use correct function for the onlineness check, use mem_cgroup_iter_break()]
  Link: https://lkml.kernel.org/r/20231205195419.2563217-1-nphamcs@gmail.com
[nphamcs@gmail.com: drop the pool's reference at the end of the writeback step]
  Link: https://lkml.kernel.org/r/20231206030627.4155634-1-nphamcs@gmail.com
Link: https://lkml.kernel.org/r/20231130194023.4102148-4-nphamcs@gmail.com
Signed-off-by: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Co-developed-by: Nhat Pham <nphamcs@gmail.com>
Signed-off-by: Nhat Pham <nphamcs@gmail.com>
Tested-by: Bagas Sanjaya <bagasdotme@gmail.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2023-12-12 10:57:01 -08:00
Hugh Dickins
ddc1a5cbc0 mempolicy: alloc_pages_mpol() for NUMA policy without vma 
Shrink shmem's stack usage by eliminating the pseudo-vma from its folio
allocation.  alloc_pages_mpol(gfp, order, pol, ilx, nid) becomes the
principal actor for passing mempolicy choice down to __alloc_pages(),
rather than vma_alloc_folio(gfp, order, vma, addr, hugepage).

vma_alloc_folio() and alloc_pages() remain, but as wrappers around
alloc_pages_mpol().  alloc_pages_bulk_*() untouched, except to provide the
additional args to policy_nodemask(), which subsumes policy_node(). 
Cleanup throughout, cutting out some unhelpful "helpers".

It would all be much simpler without MPOL_INTERLEAVE, but that adds a
dynamic to the constant mpol: complicated by v3.6 commit 09c231cb8b
("tmpfs: distribute interleave better across nodes"), which added ino bias
to the interleave, hidden from mm/mempolicy.c until this commit.

Hence "ilx" throughout, the "interleave index".  Originally I thought it
could be done just with nid, but that's wrong: the nodemask may come from
the shared policy layer below a shmem vma, or it may come from the task
layer above a shmem vma; and without the final nodemask then nodeid cannot
be decided.  And how ilx is applied depends also on page order.

The interleave index is almost always irrelevant unless MPOL_INTERLEAVE:
with one exception in alloc_pages_mpol(), where the NO_INTERLEAVE_INDEX
passed down from vma-less alloc_pages() is also used as hint not to use
THP-style hugepage allocation - to avoid the overhead of a hugepage arg
(though I don't understand why we never just added a GFP bit for THP - if
it actually needs a different allocation strategy from other pages of the
same order).  vma_alloc_folio() still carries its hugepage arg here, but
it is not used, and should be removed when agreed.

get_vma_policy() no longer allows a NULL vma: over time I believe we've
eradicated all the places which used to need it e.g.  swapoff and madvise
used to pass NULL vma to read_swap_cache_async(), but now know the vma.

[hughd@google.com: handle NULL mpol being passed to __read_swap_cache_async()]
  Link: https://lkml.kernel.org/r/ea419956-4751-0102-21f7-9c93cb957892@google.com
Link: https://lkml.kernel.org/r/74e34633-6060-f5e3-aee-7040d43f2e93@google.com
Link: https://lkml.kernel.org/r/1738368e-bac0-fd11-ed7f-b87142a939fe@google.com
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Tejun heo <tj@kernel.org>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Cc: Domenico Cerasuolo <mimmocerasuolo@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2023-10-25 16:47:16 -07:00
Suren Baghdasaryan
b243dcbf2f swap: remove remnants of polling from read_swap_cache_async 
Patch series "Per-VMA lock support for swap and userfaults", v7.

When per-VMA locks were introduced in [1] several types of page faults
would still fall back to mmap_lock to keep the patchset simple.  Among
them are swap and userfault pages.  The main reason for skipping those
cases was the fact that mmap_lock could be dropped while handling these
faults and that required additional logic to be implemented.  Implement
the mechanism to allow per-VMA locks to be dropped for these cases.

First, change handle_mm_fault to drop per-VMA locks when returning
VM_FAULT_RETRY or VM_FAULT_COMPLETED to be consistent with the way
mmap_lock is handled.  Then change folio_lock_or_retry to accept vm_fault
and return vm_fault_t which simplifies later patches.  Finally allow swap
and uffd page faults to be handled under per-VMA locks by dropping per-VMA
and retrying, the same way it's done under mmap_lock.  Naturally, once VMA
lock is dropped that VMA should be assumed unstable and can't be used.


This patch (of 6):

Commit [1] introduced IO polling support duding swapin to reduce swap read
latency for block devices that can be polled.  However later commit [2]
removed polling support.  Therefore it seems safe to remove do_poll
parameter in read_swap_cache_async and always call swap_readpage with
synchronous=false waiting for IO completion in folio_lock_or_retry.

[1] commit 23955622ff ("swap: add block io poll in swapin path")
[2] commit 9650b453a3 ("block: ignore RWF_HIPRI hint for sync dio")

Link: https://lkml.kernel.org/r/20230630211957.1341547-1-surenb@google.com
Link: https://lkml.kernel.org/r/20230630211957.1341547-2-surenb@google.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Suggested-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: Laurent Dufour <ldufour@linux.ibm.com>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Michel Lespinasse <michel@lespinasse.org>
Cc: Minchan Kim <minchan@google.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Punit Agrawal <punit.agrawal@bytedance.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2023-08-24 16:20:16 -07:00
Christoph Hellwig
e3e2762bd3 mm: remove the __swap_writepage return value 
__swap_writepage always returns 0.

Link: https://lkml.kernel.org/r/20230125133436.447864-6-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Keith Busch <kbusch@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2023-02-02 22:33:33 -08:00