This is a note to let you know that I've just added the patch titled
mm: zswap: fix missing folio cleanup in writeback race path
to the 6.7-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mm-zswap-fix-missing-folio-cleanup-in-writeback-race-path.patch
and it can be found in the queue-6.7 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From e3b63e966cac0bf78aaa1efede1827a252815a1d Mon Sep 17 00:00:00 2001
From: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
Date: Thu, 25 Jan 2024 08:51:27 +0000
Subject: mm: zswap: fix missing folio cleanup in writeback race path
From: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
commit e3b63e966cac0bf78aaa1efede1827a252815a1d upstream.
In zswap_writeback_entry(), after we get a folio from
__read_swap_cache_async(), we grab the tree lock again to check that the
swap entry was not invalidated and recycled. If it was, we delete the
folio we just added to the swap cache and exit.
However, __read_swap_cache_async() returns the folio locked when it is
newly allocated, which is always true for this path, and the folio is
ref'd. Make sure to unlock and put the folio before returning.
This was discovered by code inspection, probably because this path handles
a race condition that should not happen often, and the bug would not crash
the system, it will only strand the folio indefinitely.
Link: https://lkml.kernel.org/r/20240125085127.1327013-1-yosryahmed@xxxxxxxxxx
Fixes: 04fc7816089c ("mm: fix zswap writeback race condition")
Signed-off-by: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
Reviewed-by: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Reviewed-by: Nhat Pham <nphamcs@xxxxxxxxx>
Cc: Domenico Cerasuolo <cerasuolodomenico@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
mm/zswap.c | 2 ++
1 file changed, 2 insertions(+)
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -1105,6 +1105,8 @@ static int zswap_writeback_entry(struct
if (zswap_rb_search(&tree->rbroot, swp_offset(entry->swpentry)) != entry) {
spin_unlock(&tree->lock);
delete_from_swap_cache(page_folio(page));
+ unlock_page(page);
+ put_page(page);
ret = -ENOMEM;
goto fail;
}
Patches currently in stable-queue which might be from yosryahmed@xxxxxxxxxx are
queue-6.7/mm-zswap-fix-missing-folio-cleanup-in-writeback-race-path.patch
queue-6.7/mm-memcontrol-clarify-swapaccount-0-deprecation-warning.patch
queue-6.7/mm-swap-fix-race-when-skipping-swapcache.patch
