This is a note to let you know that I've just added the patch titled
zsmalloc: fix races between modifications of fullness and isolated
to the 6.1-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:
zsmalloc-fix-races-between-modifications-of-fullness.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 949c063d056a95ddf69de6c8666f48c55f584fc6
Author: Andrew Yang <andrew.yang@xxxxxxxxxxxx>
Date: Fri Jul 21 14:37:01 2023 +0800
zsmalloc: fix races between modifications of fullness and isolated
[ Upstream commit 4b5d1e47b69426c0f7491d97d73ad0152d02d437 ]
We encountered many kernel exceptions of VM_BUG_ON(zspage->isolated ==
0) in dec_zspage_isolation() and BUG_ON(!pages[1]) in zs_unmap_object()
lately. This issue only occurs when migration and reclamation occur at
the same time.
With our memory stress test, we can reproduce this issue several times
a day. We have no idea why no one else encountered this issue. BTW,
we switched to the new kernel version with this defect a few months
ago.
Since fullness and isolated share the same unsigned int, modifications of
them should be protected by the same lock.
[andrew.yang@xxxxxxxxxxxx: move comment]
Link: https://lkml.kernel.org/r/20230727062910.6337-1-andrew.yang@xxxxxxxxxxxx
Link: https://lkml.kernel.org/r/20230721063705.11455-1-andrew.yang@xxxxxxxxxxxx
Fixes: c4549b871102 ("zsmalloc: remove zspage isolation for migration")
Signed-off-by: Andrew Yang <andrew.yang@xxxxxxxxxxxx>
Reviewed-by: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
Cc: AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx>
Cc: Matthias Brugger <matthias.bgg@xxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 326faa751f0a4..2f5e6d35b03bd 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -1816,6 +1816,7 @@ static void replace_sub_page(struct size_class *class, struct zspage *zspage,
static bool zs_page_isolate(struct page *page, isolate_mode_t mode)
{
+ struct zs_pool *pool;
struct zspage *zspage;
/*
@@ -1826,9 +1827,10 @@ static bool zs_page_isolate(struct page *page, isolate_mode_t mode)
VM_BUG_ON_PAGE(PageIsolated(page), page);
zspage = get_zspage(page);
- migrate_write_lock(zspage);
+ pool = zspage->pool;
+ spin_lock(&pool->lock);
inc_zspage_isolation(zspage);
- migrate_write_unlock(zspage);
+ spin_unlock(&pool->lock);
return true;
}
@@ -1895,12 +1897,12 @@ static int zs_page_migrate(struct page *newpage, struct page *page,
kunmap_atomic(s_addr);
replace_sub_page(class, zspage, newpage, page);
+ dec_zspage_isolation(zspage);
/*
* Since we complete the data copy and set up new zspage structure,
* it's okay to release the pool's lock.
*/
spin_unlock(&pool->lock);
- dec_zspage_isolation(zspage);
migrate_write_unlock(zspage);
get_page(newpage);
@@ -1917,15 +1919,17 @@ static int zs_page_migrate(struct page *newpage, struct page *page,
static void zs_page_putback(struct page *page)
{
+ struct zs_pool *pool;
struct zspage *zspage;
VM_BUG_ON_PAGE(!PageMovable(page), page);
VM_BUG_ON_PAGE(!PageIsolated(page), page);
zspage = get_zspage(page);
- migrate_write_lock(zspage);
+ pool = zspage->pool;
+ spin_lock(&pool->lock);
dec_zspage_isolation(zspage);
- migrate_write_unlock(zspage);
+ spin_unlock(&pool->lock);
}
static const struct movable_operations zsmalloc_mops = {
