The patch titled
Subject: ucounts: move kfree() out of critical zone protected by ucounts_lock
has been added to the -mm mm-nonmm-unstable branch. Its filename is
ucounts-move-kfree-out-of-critical-zone-protected-by-ucounts_lock.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/ucounts-move-kfree-out-of-critical-zone-protected-by-ucounts_lock.patch
This patch will later appear in the mm-nonmm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: MengEn Sun <mengensun@xxxxxxxxxxx>
Subject: ucounts: move kfree() out of critical zone protected by ucounts_lock
Date: Fri, 6 Dec 2024 12:13:47 +0800
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@xxxxxxxxxxx
Signed-off-by: MengEn Sun <mengensun@xxxxxxxxxxx>
Reviewed-by: YueHong Wu <yuehongwu@xxxxxxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Andrei Vagin <avagin@xxxxxxxxxx>
Cc: Joel Granados <joel.granados@xxxxxxxxxx>
Cc: Thomas WeiÃ?schuh <linux@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/ucount.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
--- a/kernel/ucount.c~ucounts-move-kfree-out-of-critical-zone-protected-by-ucounts_lock
+++ a/kernel/ucount.c
@@ -164,8 +164,8 @@ struct ucounts *get_ucounts(struct ucoun
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 use
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;
_
Patches currently in -mm which might be from mengensun@xxxxxxxxxxx are
ucounts-move-kfree-out-of-critical-zone-protected-by-ucounts_lock.patch
