Patch "xfs: Don't wrap growfs AGFL indexes" has been added to the 4.6-stable tree

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

xfs: Don't wrap growfs AGFL indexes

to the 4.6-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:
xfs-don-t-wrap-growfs-agfl-indexes.patch
and it can be found in the queue-4.6 subdirectory.

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

From: Dave Chinner <[email protected]>
Date: Wed, 6 Apr 2016 07:06:20 +1000
Subject: xfs: Don't wrap growfs AGFL indexes

From: Dave Chinner <[email protected]>

commit ad747e3b299671e1a53db74963cc6c5f6cdb9f6d upstream.

Commit 96f859d ("libxfs: pack the agfl header structure so XFS_AGFL_SIZE is correct") allowed the freelist to use the empty slot at the end of the freelist on 64 bit systems that was not being used due to sizeof() rounding up the structure size.

This has caused versions of xfs_repair prior to 4.5.0 (which also has the fix) to report this as a corruption once the filesystem has been grown. Older kernels can also have problems (seen from a whacky container/vm management environment) mounting filesystems grown on a system with a newer kernel than the vm/container it is deployed on.

To avoid this problem, change the initial free list indexes not to wrap across the end of the AGFL, hence avoiding the initialisation of agf_fllast to the last index in the AGFL.

---
 fs/xfs/xfs_fsops.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

@@ -243,8 +243,8 @@ xfs_growfs_data_private(
 		agf->agf_roots[XFS_BTNUM_CNTi] = cpu_to_be32(XFS_CNT_BLOCK(mp));
 		agf->agf_levels[XFS_BTNUM_BNOi] = cpu_to_be32(1);
 		agf->agf_levels[XFS_BTNUM_CNTi] = cpu_to_be32(1);
-		agf->agf_flfirst = 0;
-		agf->agf_fllast = cpu_to_be32(XFS_AGFL_SIZE(mp) - 1);
+		agf->agf_flfirst = cpu_to_be32(1);
+		agf->agf_fllast = 0;
 		agf->agf_flcount = 0;
 		tmpsize = agsize - XFS_PREALLOC_BLOCKS(mp);
 		agf->agf_freeblks = cpu_to_be32(tmpsize);

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

queue-4.6/xfs-xfs_iflush_cluster-fails-to-abort-on-error.patch queue-4.6/xfs-disallow-rw-remount-on-fs-with-unknown-ro-compat-features.patch queue-4.6/xfs-fix-inode-validity-check-in-xfs_iflush_cluster.patch queue-4.6/xfs-skip-stale-inodes-in-xfs_iflush_cluster.patch queue-4.6/xfs-remove-xfs_fs_evict_inode.patch queue-4.6/xfs-don-t-wrap-growfs-agfl-indexes.patch