linux-kernel - [PATCH 3.19.y-ckt 021/107] ext4: replace open coded nofail allocation in ext4_free

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Message-Id: <1438811379-384-22-git-send-email-kamal@canonical.com>
Date:	Wed,  5 Aug 2015 14:48:13 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Michal Hocko <mhocko@...e.cz>, Theodore Ts'o <tytso@....edu>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.19.y-ckt 021/107] ext4: replace open coded nofail allocation in ext4_free_blocks()

3.19.8-ckt5 -stable review patch.  If anyone has any objections, please let me know.

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

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

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: Kamal Mostafa <kamal@...onical.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 8d1e602..4126048 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -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;
-- 
1.9.1

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