The patch titled
Subject: mm: zswap: make the lock critical section obvious in shrink_worker()
has been added to the -mm mm-unstable branch. Its filename is
mm-zswap-make-the-lock-critical-section-obvious-in-shrink_worker.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-zswap-make-the-lock-critical-section-obvious-in-shrink_worker.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
Subject: mm: zswap: make the lock critical section obvious in shrink_worker()
Date: Sat, 3 Aug 2024 05:33:06 +0000
Move the comments and spin_{lock/unlock}() calls around in shrink_worker()
to make it obvious the lock is protecting the loop updating
zswap_next_shrink.
Link: https://lkml.kernel.org/r/20240803053306.2685541-1-yosryahmed@xxxxxxxxxx
Signed-off-by: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
Cc: Chengming Zhou <chengming.zhou@xxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Nhat Pham <nphamcs@xxxxxxxxx>
Cc: Takero Funaki <flintglass@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/zswap.c | 14 ++++++--------
1 file changed, 6 insertions(+), 8 deletions(-)
--- a/mm/zswap.c~mm-zswap-make-the-lock-critical-section-obvious-in-shrink_worker
+++ a/mm/zswap.c
@@ -1364,24 +1364,22 @@ static void shrink_worker(struct work_st
* until the next run of shrink_worker().
*/
do {
- spin_lock(&zswap_shrink_lock);
-
/*
* Start shrinking from the next memcg after zswap_next_shrink.
* When the offline cleaner has already advanced the cursor,
* advancing the cursor here overlooks one memcg, but this
* should be negligibly rare.
+ *
+ * If we get an online memcg, keep the extra reference in case
+ * the original one obtained by mem_cgroup_iter() is dropped by
+ * zswap_memcg_offline_cleanup() while we are shrinking the
+ * memcg.
*/
+ spin_lock(&zswap_shrink_lock);
do {
memcg = mem_cgroup_iter(NULL, zswap_next_shrink, NULL);
zswap_next_shrink = memcg;
} while (memcg && !mem_cgroup_tryget_online(memcg));
- /*
- * Note that if we got an online memcg, we will keep the extra
- * reference in case the original reference obtained by mem_cgroup_iter
- * is dropped by the zswap memcg offlining callback, ensuring that the
- * memcg is not killed when we are reclaiming.
- */
spin_unlock(&zswap_shrink_lock);
if (!memcg) {
_
Patches currently in -mm which might be from yosryahmed@xxxxxxxxxx are
mm-zswap-make-the-lock-critical-section-obvious-in-shrink_worker.patch
