From: Theodore Ts'o <tytso@mit.edu>
Date: Sat, 13 Jul 2013 04:40:35 +0000 (-0400)
Subject: ext4: don't allow ext4_free_blocks() to fail due to ENOMEM
X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=e7676a704ee0a1ef71a6b23760b5a8f6896cb1a1;p=openwrt%2Fstaging%2Fblogic.git

ext4: don't allow ext4_free_blocks() to fail due to ENOMEM

The filesystem should not be marked inconsistent if ext4_free_blocks()
is not able to allocate memory.  Unfortunately some callers (most
notably ext4_truncate) don't have a way to reflect an error back up to
the VFS.  And even if we did, most userspace applications won't deal
with most system calls returning ENOMEM anyway.

Reported-by: Nagachandra P <nagachandra@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@vger.kernel.org
---

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index a9ff5e5137ca..4bbbf13bd743 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -4740,11 +4740,16 @@ do_more:
 		 * blocks being freed are metadata. these blocks shouldn't
 		 * be used until this transaction is committed
 		 */
+	retry:
 		new_entry = kmem_cache_alloc(ext4_free_data_cachep, GFP_NOFS);
 		if (!new_entry) {
-			ext4_mb_unload_buddy(&e4b);
-			err = -ENOMEM;
-			goto error_return;
+			/*
+			 * 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->efd_start_cluster = bit;
 		new_entry->efd_group = block_group;