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zsmalloc: fix races between modifications of fullness and isolated 

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@mediatek.com: move comment]
  Link: https://lkml.kernel.org/r/20230727062910.6337-1-andrew.yang@mediatek.com
Link: https://lkml.kernel.org/r/20230721063705.11455-1-andrew.yang@mediatek.com
Fixes: c4549b8711 ("zsmalloc: remove zspage isolation for migration")
Signed-off-by: Andrew Yang <andrew.yang@mediatek.com>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Andrew Yang 2023-07-21 14:37:01 +08:00 committed by Andrew Morton
parent 5d0c230f1d
commit 4b5d1e47b6
1 changed files with 9 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
mm/zsmalloc.c
View File

@ -1798,6 +1798,7 @@ 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;
/*
@ -1807,9 +1808,10 @@ 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;
}
@ -1875,12 +1877,12 @@ 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);
@ -1897,14 +1899,16 @@ 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(!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 = {