xfs_repair: clear inodes in incorrect btree format

xfs_repair: clear inodes in incorrect btree format

See also RH bug #510823:
https://bugzilla.redhat.com/show_bug.cgi?id=510823

This check in xfs_iformat_btree() tripped:

        /*
         * blow out if -- fork has less extents than can fit in
         * fork (fork shouldn't be a btree format), root btree
         * block has more records than can fit into the fork,
         * or the number of extents is greater than the number of
         * blocks.
         */

leading to:

Jul 10 23:22:45 hermes kernel: Filesystem "dm-11": corrupt inode 2339503222
(btree).  Unmount and run xfs_repair.
Jul 10 23:22:45 hermes kernel: Filesystem "dm-11": XFS internal error
xfs_iformat_btree at line 625 of file fs/xfs/xfs_inode.c.

but repair finds nothing at all.  xfs_check, however, does flag the inodes
as problematic:

extent count for ino 2339503222 data fork too low (6) for file format

So I copied the xfs_check test into xfs_repair, and voila, it clears
these inodes.

Ideally repair would move these back into extent format, as long as
they are all valid.  But I need to look further at that, and for now
there is no other way out of the situation when the kernel finds
the problematic inode, so I'll commit this as a first step.

Signed-off-by: Eric Sandeen <sandeen@sandeen.net>
Acked-By: Olaf Weber <olaf@sgi.com>
Reviewed-by: Christoph Hellwig <hch@infradead.org>