linux-kernel - [PATCH 3.4 005/107] ext4: replace open coded nofail allocation in ext4_free

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Message-Id: <1458115601-5762-5-git-send-email-lizf@kernel.org>
Date:	Wed, 16 Mar 2016 16:04:59 +0800
From:	lizf@...nel.org
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, Michal Hocko <mhocko@...e.cz>,
	Theodore Ts'o <tytso@....edu>, Zefan Li <lizefan@...wei.com>
Subject: [PATCH 3.4 005/107] ext4: replace open coded nofail allocation in ext4_free_blocks()

From: Michal Hocko <mhocko@...e.cz>

3.4.111-rc1 review patch.  If anyone has any objections, please let me know.

------------------


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.

Signed-off-by: Michal Hocko <mhocko@...e.cz>
Signed-off-by: Theodore Ts'o <tytso@....edu>
Signed-off-by: Zefan Li <lizefan@...wei.com>
---
 fs/ext4/mballoc.c | 16 +++++-----------
 1 file changed, 5 insertions(+), 11 deletions(-)

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index cdfc763..46e6562 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -4643,18 +4643,12 @@ 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;
-- 
1.9.1