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ucounts: move kfree() out of critical zone protected by ucounts_lock

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Although kfree is a non-sleep function, it is possible to enter a long
chain of calls probabilistically, so it looks better to move kfree from
alloc_ucounts() out of the critical zone of ucounts_lock.

Link: https://lkml.kernel.org/r/1733458427-11794-1-git-send-email-mengensun@tencent.com
Signed-off-by: MengEn Sun <mengensun@tencent.com>
Reviewed-by: YueHong Wu <yuehongwu@tencent.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrei Vagin <avagin@google.com>
Cc: Joel Granados <joel.granados@kernel.org>
Cc: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
MengEn Sun 2024-12-06 12:13:47 +08:00 committed by Andrew Morton
parent 2616a8828b
commit 2b05eacc98
1 changed files with 4 additions and 4 deletions
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8
kernel/ucount.c
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@ -164,8 +164,8 @@ struct ucounts *get_ucounts(struct ucounts *ucounts)
struct ucounts *alloc_ucounts(struct user_namespace *ns, kuid_t uid)
{
struct hlist_head *hashent = ucounts_hashentry(ns, uid);
struct ucounts *ucounts, *new;
bool wrapped;
struct ucounts *ucounts, *new = NULL;
spin_lock_irq(&ucounts_lock);
ucounts = find_ucounts(ns, uid, hashent);
@ -182,17 +182,17 @@ struct ucounts *alloc_ucounts(struct user_namespace *ns, kuid_t uid)
spin_lock_irq(&ucounts_lock);
ucounts = find_ucounts(ns, uid, hashent);
if (ucounts) {
kfree(new);
} else {
if (!ucounts) {
hlist_add_head(&new->node, hashent);
get_user_ns(new->ns);
spin_unlock_irq(&ucounts_lock);
return new;
}
}
wrapped = !get_ucounts_or_wrap(ucounts);
spin_unlock_irq(&ucounts_lock);
kfree(new);
if (wrapped) {
put_ucounts(ucounts);
return NULL;