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Commit 5c9bab59 authored by Vitaly Wool's avatar Vitaly Wool Committed by Linus Torvalds
Browse files

z3fold: limit use of stale list for allocation 

Currently if z3fold couldn't find an unbuddied page it would first try
to pull a page off the stale list.  The problem with this approach is
that we can't 100% guarantee that the page is not processed by the
workqueue thread at the same time unless we run cancel_work_sync() on
it, which we can't do if we're in an atomic context.  So let's just
limit stale list usage to non-atomic contexts only.

Link: http://lkml.kernel.org/r/47ab51e7-e9c1-d30e-ab17-f734dbc3abce@gmail.com


Signed-off-by: default avatarVitaly Vul <vitaly.vul@sony.com>
Reviewed-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Cc: <Oleksiy.Avramchenko@sony.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 605ca5ed

mm/z3fold.c

+19 −16
Original line number Diff line number Diff line
@@ -620,24 +620,27 @@ static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp, 
		bud = FIRST;

	}



	page = NULL;

	if (can_sleep) {

		spin_lock(&pool->stale_lock);

		zhdr = list_first_entry_or_null(&pool->stale,

						struct z3fold_header, buddy);

		/*

	 * Before allocating a page, let's see if we can take one from the

	 * 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.

		 * Before allocating a page, let's see if we can take one from

		 * the stale pages list. cancel_work_sync() can sleep so we

		 * limit this case to the contexts where we can sleep

		 */

	if (zhdr && (can_sleep || !work_pending(&zhdr->work))) {

		if (zhdr) {

			list_del(&zhdr->buddy);

			spin_unlock(&pool->stale_lock);

		if (can_sleep)

			cancel_work_sync(&zhdr->work);

			page = virt_to_page(zhdr);

		} else {

			spin_unlock(&pool->stale_lock);

		page = alloc_page(gfp);

		}

	}

	if (!page)

		page = alloc_page(gfp);



	if (!page)

		return -ENOMEM;