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Shivank Garg 5173ae0a06 mm/khugepaged: map dirty/writeback pages failures to EAGAIN 
Patch series "mm/khugepaged: fix dirty page handling for MADV_COLLAPSE",
v5.

MADV_COLLAPSE on file-backed mappings fails with -EINVAL when TEXT pages
are dirty. This affects scenarios like package/container updates or
executing binaries immediately after writing them, etc.

The issue is that collapse_file() triggers async writeback and returns
SCAN_FAIL (maps to -EINVAL), expecting khugepaged to revisit later. But
MADV_COLLAPSE is synchronous and userspace expects immediate success or
a clear retry signal.

Reproduction:
 - Compile or copy 2MB-aligned executable to XFS/ext4 FS
 - Call MADV_COLLAPSE on .text section
 - First call fails with -EINVAL (text pages dirty from copy)
 - Second call succeeds (async writeback completed)

Issue Report:
https://lore.kernel.org/all/4e26fe5e-7374-467c-a333-9dd48f85d7cc@amd.com


This patch (of 2):

When collapse_file encounters dirty or writeback pages in file-backed
mappings, it currently returns SCAN_FAIL which maps to -EINVAL.  This is
misleading as EINVAL suggests invalid arguments, whereas dirty/writeback
pages represent transient conditions that may resolve on retry.

Introduce SCAN_PAGE_DIRTY_OR_WRITEBACK to cover both dirty and writeback
states, mapping it to -EAGAIN.  For MADV_COLLAPSE, this provides userspace
with a clear signal that retry may succeed after writeback completes.  For
khugepaged, this is harmless as it will naturally revisit the range during
periodic scans after async writeback completes.

Link: https://lkml.kernel.org/r/20260118190939.8986-2-shivankg@amd.com
Link: https://lkml.kernel.org/r/20260118190939.8986-4-shivankg@amd.com
Fixes: 34488399fa ("mm/madvise: add file and shmem support to MADV_COLLAPSE")
Signed-off-by: Shivank Garg <shivankg@amd.com>
Reported-by: Branden Moore <Branden.Moore@amd.com>
Closes: https://lore.kernel.org/all/4e26fe5e-7374-467c-a333-9dd48f85d7cc@amd.com
Reviewed-by: Dev Jain <dev.jain@arm.com>
Reviewed-by: Lance Yang <lance.yang@linux.dev>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: wang lian <lianux.mm@gmail.com>
Acked-by: David Hildenbrand (Red Hat) <david@kernel.org>
Cc: Barry Song <baohua@kernel.org>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Nico Pache <npache@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2026-01-26 20:02:12 -08:00
..
acpi ACPI: PCI: IRQ: Fix INTx GSIs signedness 2026-01-05 19:06:40 +01:00
asm-generic mm/mmu_gather: remove @delay_remap of __tlb_remove_page_size() 2026-01-20 19:24:54 -08:00
clocksource
crypto This update includes the following changes: 2025-12-03 11:28:38 -08:00
cxl
drm drm-misc-fixes for v6.19-rc6: 2026-01-16 20:27:21 +01:00
dt-bindings This pull request is entirely SoC clk drivers, not for lack of trying to modify 2025-12-08 09:38:52 +09:00
hyperv hyperv: Avoid -Wflex-array-member-not-at-end warning 2025-12-18 19:42:01 +00:00
keys
kunit kunit: Enforce task execution in {soft,hard}irq contexts 2025-12-22 12:20:08 -08:00
kvm
linux mm/vmstat: remove unused node and zone state helpers 2026-01-20 19:24:52 -08:00
math-emu
media
memory
misc
net net: add net.core.qdisc_max_burst 2026-01-13 10:12:11 +01:00
pcmcia
ras Significant patch series in this merge are as follows: 2025-12-05 13:52:43 -08:00
rdma
rv rv: Fix compilation if !CONFIG_RV_REACTORS 2025-12-02 12:33:37 -05:00
scsi scsi: core: Fix error handler encryption support 2026-01-04 15:16:20 -05:00
soc This pull request is entirely SoC clk drivers, not for lack of trying to modify 2025-12-08 09:38:52 +09:00
sound ALSA: pcm: Improve the fix for race of buffer access at PCM OSS layer 2026-01-08 08:07:54 +01:00
target
trace mm/khugepaged: map dirty/writeback pages failures to EAGAIN 2026-01-26 20:02:12 -08:00
uapi mm/block/fs: remove laptop_mode 2026-01-20 19:24:47 -08:00
ufs
vdso
video
xen
Kbuild