[3.19.y-ckt stable] Patch "libxfs: pack the agfl header structure so XFS_AGFL_SIZE is correct" has been added to the 3.19.y-ckt tree

[Kamal Mostafa]

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

    libxfs: pack the agfl header structure so XFS_AGFL_SIZE is correct

to the linux-3.19.y-queue branch of the 3.19.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.19.y-queue

This patch is scheduled to be released in version 3.19.8-ckt14.

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

For more information about the 3.19.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

---8<------------------------------------------------------------

>From 6e187000877509a21659475e5d09a699f6a23cd3 Mon Sep 17 00:00:00 2001
From: "Darrick J. Wong" <darrick.wong at oracle.com>
Date: Mon, 4 Jan 2016 16:13:21 +1100
Subject: libxfs: pack the agfl header structure so XFS_AGFL_SIZE is correct

commit 96f859d52bcb1c6ea6f3388d39862bf7143e2f30 upstream.

Because struct xfs_agfl is 36 bytes long and has a 64-bit integer
inside it, gcc will quietly round the structure size up to the nearest
64 bits -- in this case, 40 bytes.  This results in the XFS_AGFL_SIZE
macro returning incorrect results for v5 filesystems on 64-bit
machines (118 items instead of 119).  As a result, a 32-bit xfs_repair
will see garbage in AGFL item 119 and complain.

Therefore, tell gcc not to pad the structure so that the AGFL size
calculation is correct.

Signed-off-by: Darrick J. Wong <darrick.wong at oracle.com>
Reviewed-by: Dave Chinner <dchinner at redhat.com>
Signed-off-by: Dave Chinner <david at fromorbit.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 fs/xfs/libxfs/xfs_format.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/xfs/libxfs/xfs_format.h b/fs/xfs/libxfs/xfs_format.h
index fbd6da2..ecf7d02 100644
--- a/fs/xfs/libxfs/xfs_format.h
+++ b/fs/xfs/libxfs/xfs_format.h
@@ -816,7 +816,7 @@ typedef struct xfs_agfl {
 	__be64		agfl_lsn;
 	__be32		agfl_crc;
 	__be32		agfl_bno[];	/* actually XFS_AGFL_SIZE(mp) */
-} xfs_agfl_t;
+} __attribute__((packed)) xfs_agfl_t;

 #define XFS_AGFL_CRC_OFF	offsetof(struct xfs_agfl, agfl_crc)

--
1.9.1