[ 3.5.y.z extended stable ] Patch "ext4: make sure group number is bumped after a inode" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    ext4: make sure group number is bumped after a inode

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From b1ae3aaeebfcecdc2be79c9fc9099725d0dfa171 Mon Sep 17 00:00:00 2001
From: Theodore Ts'o <tytso at mit.edu>
Date: Fri, 26 Jul 2013 15:15:46 -0400
Subject: [PATCH] ext4: make sure group number is bumped after a inode
 allocation race

commit a34eb503742fd25155fd6cff6163daacead9fbc3 upstream.

When we try to allocate an inode, and there is a race between two
CPU's trying to grab the same inode, _and_ this inode is the last free
inode in the block group, make sure the group number is bumped before
we continue searching the rest of the block groups.  Otherwise, we end
up searching the current block group twice, and we end up skipping
searching the last block group.  So in the unlikely situation where
almost all of the inodes are allocated, it's possible that we will
return ENOSPC even though there might be free inodes in that last
block group.

Signed-off-by: "Theodore Ts'o" <tytso at mit.edu>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 fs/ext4/ialloc.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index b1919af..fa068c0 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -707,11 +707,8 @@ repeat_in_this_group:
 		ino = ext4_find_next_zero_bit((unsigned long *)
 					      inode_bitmap_bh->b_data,
 					      EXT4_INODES_PER_GROUP(sb), ino);
-		if (ino >= EXT4_INODES_PER_GROUP(sb)) {
-			if (++group == ngroups)
-				group = 0;
-			continue;
-		}
+		if (ino >= EXT4_INODES_PER_GROUP(sb))
+			goto next_group;
 		if (group == 0 && (ino+1) < EXT4_FIRST_INO(sb)) {
 			ext4_error(sb, "reserved inode found cleared - "
 				   "inode=%lu", ino + 1);
@@ -729,6 +726,9 @@ repeat_in_this_group:
 			goto got; /* we grabbed the inode! */
 		if (ino < EXT4_INODES_PER_GROUP(sb))
 			goto repeat_in_this_group;
+next_group:
+		if (++group == ngroups)
+			group = 0;
 	}
 	err = -ENOSPC;
 	goto out;
--
1.8.3.2