Merge git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux

1 files changed, 17 insertions, 5 deletions

diff --git a/mm/mempool.c b/mm/mempool.c
index 004d42b1dfaf..07c383ddbbab 100644
--- a/mm/mempool.c
+++ b/mm/mempool.c
@@ -135,8 +135,8 @@ static void *remove_element(mempool_t *pool)
 	void *element = pool->elements[--pool->curr_nr];
 
 	BUG_ON(pool->curr_nr < 0);
-	check_element(pool, element);
 	kasan_unpoison_element(pool, element);
+	check_element(pool, element);
 	return element;
 }
 
@@ -310,25 +310,36 @@ EXPORT_SYMBOL(mempool_resize);
  * returns NULL. Note that due to preallocation, this function
  * *never* fails when called from process contexts. (it might
  * fail if called from an IRQ context.)
- * Note: using __GFP_ZERO is not supported.
+ * Note: neither __GFP_NOMEMALLOC nor __GFP_ZERO are supported.
  */
-void * mempool_alloc(mempool_t *pool, gfp_t gfp_mask)
+void *mempool_alloc(mempool_t *pool, gfp_t gfp_mask)
 {
 	void *element;
 	unsigned long flags;
 	wait_queue_t wait;
 	gfp_t gfp_temp;
 
+	/* If oom killed, memory reserves are essential to prevent livelock */
+	VM_WARN_ON_ONCE(gfp_mask & __GFP_NOMEMALLOC);
+	/* No element size to zero on allocation */
 	VM_WARN_ON_ONCE(gfp_mask & __GFP_ZERO);
+
 	might_sleep_if(gfp_mask & __GFP_DIRECT_RECLAIM);
 
-	gfp_mask |= __GFP_NOMEMALLOC;	/* don't allocate emergency reserves */
 	gfp_mask |= __GFP_NORETRY;	/* don't loop in __alloc_pages */
 	gfp_mask |= __GFP_NOWARN;	/* failures are OK */
 
 	gfp_temp = gfp_mask & ~(__GFP_DIRECT_RECLAIM|__GFP_IO);
 
 repeat_alloc:
+	if (likely(pool->curr_nr)) {
+		/*
+		 * Don't allocate from emergency reserves if there are
+		 * elements available.  This check is racy, but it will
+		 * be rechecked each loop.
+		 */
+		gfp_temp |= __GFP_NOMEMALLOC;
+	}
 
 	element = pool->alloc(gfp_temp, pool->pool_data);
 	if (likely(element != NULL))
@@ -352,11 +363,12 @@ repeat_alloc:
 	 * We use gfp mask w/o direct reclaim or IO for the first round.  If
 	 * alloc failed with that and @pool was empty, retry immediately.
 	 */
-	if (gfp_temp != gfp_mask) {
+	if ((gfp_temp & ~__GFP_NOMEMALLOC) != gfp_mask) {
 		spin_unlock_irqrestore(&pool->lock, flags);
 		gfp_temp = gfp_mask;
 		goto repeat_alloc;
 	}
+	gfp_temp = gfp_mask;
 
 	/* We must not sleep if !__GFP_DIRECT_RECLAIM */
 	if (!(gfp_mask & __GFP_DIRECT_RECLAIM)) {