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bpf: Convert bpf_selem_unlink to failable

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To prepare changing both bpf_local_storage_map_bucket::lock and
bpf_local_storage::lock to rqspinlock, convert bpf_selem_unlink() to
failable. It still always succeeds and returns 0 until the change
happens. No functional change.

Open code bpf_selem_unlink_storage() in the only caller,
bpf_selem_unlink(), since unlink_map and unlink_storage must be done
together after all the necessary locks are acquired.

For bpf_local_storage_map_free(), ignore the return from
bpf_selem_unlink() for now. A later patch will allow it to unlink selems
even when failing to acquire locks.

Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Amery Hung <ameryhung@gmail.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://patch.msgid.link/20260205222916.1788211-5-ameryhung@gmail.com
This commit is contained in:
Amery Hung 2026-02-05 14:29:02 -08:00 • committed by Martin KaFai Lau
parent fd103ffc57
commit 403e935f91
6 changed files with 39 additions and 49 deletions
Download patch file Download diff file Expand all files Collapse all files

2
include/linux/bpf_local_storage.h
View file

@ -176,7 +176,7 @@ int bpf_local_storage_map_check_btf(const struct bpf_map *map,
void bpf_selem_link_storage_nolock(struct bpf_local_storage *local_storage,
struct bpf_local_storage_elem *selem);
void bpf_selem_unlink(struct bpf_local_storage_elem *selem, bool reuse_now);
int bpf_selem_unlink(struct bpf_local_storage_elem *selem, bool reuse_now);
int bpf_selem_link_map(struct bpf_local_storage_map *smap,
struct bpf_local_storage *local_storage,

3
kernel/bpf/bpf_cgrp_storage.c
View file

@ -118,8 +118,7 @@ static int cgroup_storage_delete(struct cgroup *cgroup, struct bpf_map *map)
if (!sdata)
return -ENOENT;
bpf_selem_unlink(SELEM(sdata), false);
return 0;
return bpf_selem_unlink(SELEM(sdata), false);
}
static long bpf_cgrp_storage_delete_elem(struct bpf_map *map, void *key)

4
kernel/bpf/bpf_inode_storage.c
View file

@ -110,9 +110,7 @@ static int inode_storage_delete(struct inode *inode, struct bpf_map *map)
if (!sdata)
return -ENOENT;
bpf_selem_unlink(SELEM(sdata), false);
return 0;
return bpf_selem_unlink(SELEM(sdata), false);
}
static long bpf_fd_inode_storage_delete_elem(struct bpf_map *map, void *key)

71
kernel/bpf/bpf_local_storage.c
View file

@ -308,33 +308,6 @@ static bool bpf_selem_unlink_storage_nolock(struct bpf_local_storage *local_stor
return free_local_storage;
}
static void bpf_selem_unlink_storage(struct bpf_local_storage_elem *selem,
bool reuse_now)
{
struct bpf_local_storage *local_storage;
bool free_local_storage = false;
HLIST_HEAD(selem_free_list);
unsigned long flags;
if (unlikely(!selem_linked_to_storage_lockless(selem)))
/* selem has already been unlinked from sk */
return;
local_storage = rcu_dereference_check(selem->local_storage,
bpf_rcu_lock_held());
raw_spin_lock_irqsave(&local_storage->lock, flags);
if (likely(selem_linked_to_storage(selem)))
free_local_storage = bpf_selem_unlink_storage_nolock(
local_storage, selem, &selem_free_list);
raw_spin_unlock_irqrestore(&local_storage->lock, flags);
bpf_selem_free_list(&selem_free_list, reuse_now);
if (free_local_storage)
bpf_local_storage_free(local_storage, reuse_now);
}
void bpf_selem_link_storage_nolock(struct bpf_local_storage *local_storage,
struct bpf_local_storage_elem *selem)
{
@ -386,19 +359,43 @@ static void bpf_selem_link_map_nolock(struct bpf_local_storage_map_bucket *b,
hlist_add_head_rcu(&selem->map_node, &b->list);
}
void bpf_selem_unlink(struct bpf_local_storage_elem *selem, bool reuse_now)
int bpf_selem_unlink(struct bpf_local_storage_elem *selem, bool reuse_now)
{
int err;
struct bpf_local_storage *local_storage;
bool free_local_storage = false;
HLIST_HEAD(selem_free_list);
unsigned long flags;
int err = 0;
/* Always unlink from map before unlinking from local_storage
* because selem will be freed after successfully unlinked from
* the local_storage.
*/
err = bpf_selem_unlink_map(selem);
if (err)
return;
if (unlikely(!selem_linked_to_storage_lockless(selem)))
/* selem has already been unlinked from sk */
return 0;
bpf_selem_unlink_storage(selem, reuse_now);
local_storage = rcu_dereference_check(selem->local_storage,
bpf_rcu_lock_held());
raw_spin_lock_irqsave(&local_storage->lock, flags);
if (likely(selem_linked_to_storage(selem))) {
/* Always unlink from map before unlinking from local_storage
* because selem will be freed after successfully unlinked from
* the local_storage.
*/
err = bpf_selem_unlink_map(selem);
if (err)
goto out;
free_local_storage = bpf_selem_unlink_storage_nolock(
local_storage, selem, &selem_free_list);
}
out:
raw_spin_unlock_irqrestore(&local_storage->lock, flags);
bpf_selem_free_list(&selem_free_list, reuse_now);
if (free_local_storage)
bpf_local_storage_free(local_storage, reuse_now);
return err;
}
void __bpf_local_storage_insert_cache(struct bpf_local_storage *local_storage,

4
kernel/bpf/bpf_task_storage.c
View file

@ -167,9 +167,7 @@ static int task_storage_delete(struct task_struct *task, struct bpf_map *map,
if (!nobusy)
return -EBUSY;
bpf_selem_unlink(SELEM(sdata), false);
return 0;
return bpf_selem_unlink(SELEM(sdata), false);
}
static long bpf_pid_task_storage_delete_elem(struct bpf_map *map, void *key)

4
net/core/bpf_sk_storage.c
View file

@ -40,9 +40,7 @@ static int bpf_sk_storage_del(struct sock *sk, struct bpf_map *map)
if (!sdata)
return -ENOENT;
bpf_selem_unlink(SELEM(sdata), false);
return 0;
return bpf_selem_unlink(SELEM(sdata), false);
}
/* Called by __sk_destruct() & bpf_sk_storage_clone() */