Patch "libxfs: pack the agfl header structure so XFS_AGFL_SIZE is correct" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

libxfs: pack the agfl header structure so XFS_AGFL_SIZE is correct

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
libxfs-pack-the-agfl-header-structure-so-xfs_agfl_size-is-correct.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: "Darrick J. Wong" <[email protected]>
Date: Mon, 4 Jan 2016 16:13:21 +1100
Subject: libxfs: pack the agfl header structure so XFS_AGFL_SIZE is correct

From: Darrick J. Wong <[email protected]>

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.

---
 fs/xfs/libxfs/xfs_format.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

@@ -786,7 +786,7 @@ 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)
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/ext4-fix-scheduling-in-atomic-on-group-checksum-failure.patch queue-4.4/libxfs-pack-the-agfl-header-structure-so-xfs_agfl_size-is-correct.patch