[3.16.y-ckt stable] Patch "xfs: set superblock buffer type correctly" has been added to staging queue

[Luis Henriques]

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

    xfs: set superblock buffer type correctly

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt8.

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

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 60f2d5945184902f30a773090d8a58a499c69990 Mon Sep 17 00:00:00 2001
From: Dave Chinner <dchinner at redhat.com>
Date: Thu, 22 Jan 2015 09:30:23 +1100
Subject: xfs: set superblock buffer type correctly

commit 3443a3bca54588f43286b725d8648d33a38c86f1 upstream.

When the superblock is modified in a transaction, the commonly
modified fields are not actually copied to the superblock buffer to
avoid the buffer lock becoming a serialisation point. However, there
are some other operations that modify the superblock fields within
the transaction that don't directly log to the superblock but rely
on the changes to be applied during the transaction commit (to
minimise the buffer lock hold time).

When we do this, we fail to mark the buffer log item as being a
superblock buffer and that can lead to the buffer not being marked
with the corect type in the log and hence causing recovery issues.
Fix it by setting the type correctly, similar to xfs_mod_sb()...

Tested-by: Jan Kara <jack at suse.cz>
Signed-off-by: Dave Chinner <dchinner at redhat.com>
Reviewed-by: Brian Foster <bfoster at redhat.com>
Signed-off-by: Dave Chinner <david at fromorbit.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 fs/xfs/xfs_trans.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c
index d03932564ccb..c81f51c290c1 100644
--- a/fs/xfs/xfs_trans.c
+++ b/fs/xfs/xfs_trans.c
@@ -474,6 +474,7 @@ xfs_trans_apply_sb_deltas(
 		whole = 1;
 	}

+	xfs_trans_buf_set_type(tp, bp, XFS_BLFT_SB_BUF);
 	if (whole)
 		/*
 		 * Log the whole thing, the fields are noncontiguous.