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/[email protected]
Signed-off-by: Vitaly Vul <[email protected]>
Reviewed-by: Andrew Morton <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
diff --git a/mm/z3fold.c b/mm/z3fold.c
index d589d31..f579ad4 100644
--- a/mm/z3fold.c
+++ b/mm/z3fold.c
@@ -620,24 +620,27 @@ static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp,
bud = FIRST;
}
- 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.
- */
- if (zhdr && (can_sleep || !work_pending(&zhdr->work))) {
- list_del(&zhdr->buddy);
- spin_unlock(&pool->stale_lock);
- if (can_sleep)
+ 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
+ * limit this case to the contexts where we can sleep
+ */
+ if (zhdr) {
+ list_del(&zhdr->buddy);
+ spin_unlock(&pool->stale_lock);
cancel_work_sync(&zhdr->work);
- page = virt_to_page(zhdr);
- } else {
- spin_unlock(&pool->stale_lock);
- page = alloc_page(gfp);
+ page = virt_to_page(zhdr);
+ } else {
+ spin_unlock(&pool->stale_lock);
+ }
}
+ if (!page)
+ page = alloc_page(gfp);
if (!page)
return -ENOMEM;
