Patch "ext4: replace open coded nofail allocation in ext4_free_blocks()" has been added to the 4.1-stable tree

This is a note to let you know that I've just added the patch titled

ext4: replace open coded nofail allocation in ext4_free_blocks()

to the 4.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
ext4-replace-open-coded-nofail-allocation-in-ext4_free_blocks.patch
and it can be found in the queue-4.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Michal Hocko <[email protected]>
Date: Sun, 5 Jul 2015 12:33:44 -0400
Subject: ext4: replace open coded nofail allocation in ext4_free_blocks()

From: Michal Hocko <[email protected]>

commit 7444a072c387a93ebee7066e8aee776954ab0e41 upstream.

ext4_free_blocks is looping around the allocation request and mimics __GFP_NOFAIL behavior without any allocation fallback strategy. Let's remove the open coded loop and replace it with __GFP_NOFAIL. Without the flag the allocator has no way to find out never-fail requirement and cannot help in any way.

---
 fs/ext4/mballoc.c |   16 +++++-----------
 1 file changed, 5 insertions(+), 11 deletions(-)

@@ -4800,18 +4800,12 @@ do_more:
 		/*
 		 * blocks being freed are metadata. these blocks shouldn't
 		 * be used until this transaction is committed
+		 *
+		 * We use __GFP_NOFAIL because ext4_free_blocks() is not allowed
+		 * to fail.
 		 */
-	retry:
-		new_entry = kmem_cache_alloc(ext4_free_data_cachep, GFP_NOFS);
-		if (!new_entry) {
-			/*
-			 * We use a retry loop because
-			 * ext4_free_blocks() is not allowed to fail.
-			 */
-			cond_resched();
-			congestion_wait(BLK_RW_ASYNC, HZ/50);
-			goto retry;
-		}
+		new_entry = kmem_cache_alloc(ext4_free_data_cachep,
+				GFP_NOFS|__GFP_NOFAIL);
 		new_entry->efd_start_cluster = bit;
 		new_entry->efd_group = block_group;
 		new_entry->efd_count = count_clusters;

Patches currently in stable-queue which might be from [email protected] are

queue-4.1/ext4-replace-open-coded-nofail-allocation-in-ext4_free_blocks.patch