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z3fold: limit use of stale list for allocation

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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: Vitaly Vul <vitaly.vul@sony.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.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 2018-04-05 16:23:32 -07:00 committed by Linus Torvalds
parent 605ca5ede7
commit 5c9bab592f
1 changed files with 19 additions and 16 deletions
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35
mm/z3fold.c
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@ -620,24 +620,27 @@ lookup:
bud = FIRST; bud = FIRST;
} }
spin_lock(&pool->stale_lock); page = NULL;
zhdr = list_first_entry_or_null(&pool->stale, if (can_sleep) {
struct z3fold_header, buddy); spin_lock(&pool->stale_lock);
/* zhdr = list_first_entry_or_null(&pool->stale,
* Before allocating a page, let's see if we can take one from the struct z3fold_header, buddy);
* 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
if (zhdr && (can_sleep || !work_pending(&zhdr->work))) { * limit this case to the contexts where we can sleep
list_del(&zhdr->buddy); */
spin_unlock(&pool->stale_lock); if (zhdr) {
if (can_sleep) list_del(&zhdr->buddy);
spin_unlock(&pool->stale_lock);
cancel_work_sync(&zhdr->work); cancel_work_sync(&zhdr->work);
page = virt_to_page(zhdr); page = virt_to_page(zhdr);
} else { } else {
spin_unlock(&pool->stale_lock); spin_unlock(&pool->stale_lock);
page = alloc_page(gfp); }
} }
if (!page)
page = alloc_page(gfp);
if (!page) if (!page)
return -ENOMEM; return -ENOMEM;