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z3fold: fix stale list handling 

Fix the situation when clear_bit() is called for page->private before
the page pointer is actually assigned.  While at it, remove work_busy()
check because it is costly and does not give 100% guarantee anyway.

Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: <Oleksiy.Avramchenko@sony.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Vitaly Wool 2017-10-03 16:15:06 -07:00 committed by Linus Torvalds
parent 6818600ff0
commit 3552935742
1 changed files with 2 additions and 4 deletions
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6
mm/z3fold.c
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@ -250,6 +250,7 @@ static void __release_z3fold_page(struct z3fold_header *zhdr, bool locked)
WARN_ON(!list_empty(&zhdr->buddy));
set_bit(PAGE_STALE, &page->private);
clear_bit(NEEDS_COMPACTING, &page->private);
spin_lock(&pool->lock);
if (!list_empty(&page->lru))
list_del(&page->lru);
@ -303,7 +304,6 @@ static void free_pages_work(struct work_struct *w)
list_del(&zhdr->buddy);
if (WARN_ON(!test_bit(PAGE_STALE, &page->private)))
continue;
clear_bit(NEEDS_COMPACTING, &page->private);
spin_unlock(&pool->stale_lock);
cancel_work_sync(&zhdr->work);
free_z3fold_page(page);
@ -624,10 +624,8 @@ lookup:
* stale pages list. cancel_work_sync() can sleep so we must make
* sure it won't be called in case we're in atomic context.
*/
if (zhdr && (can_sleep || !work_pending(&zhdr->work) ||
!unlikely(work_busy(&zhdr->work)))) {
if (zhdr && (can_sleep || !work_pending(&zhdr->work))) {
list_del(&zhdr->buddy);
clear_bit(NEEDS_COMPACTING, &page->private);
spin_unlock(&pool->stale_lock);
if (can_sleep)
cancel_work_sync(&zhdr->work);