xfs: add CRC checks to the AGFL

Add CRC checks, location information and a magic number to the AGFL.
Previously the AGFL was just a block containing nothing but the
free block pointers.  The new AGFL has a real header with the usual
boilerplate instead, so that we can verify it's not corrupted and
written into the right place.

[dchinner@redhat.com] Added LSN field, reworked significantly to fit
into new verifier structure and growfs structure, enabled full
verifier functionality now there is a header to verify and we can
guarantee an initialised AGFL.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Ben Myers <bpm@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c
index b6cca27e9132..a693a54799e5 100644
--- a/fs/xfs/xfs_fsops.c
+++ b/fs/xfs/xfs_fsops.c
@@ -268,6 +268,11 @@ xfs_growfs_data_private(
                 }
 
                 agfl = XFS_BUF_TO_AGFL(bp);
+                if (xfs_sb_version_hascrc(&mp->m_sb)) {
+                        agfl->agfl_magicnum = cpu_to_be32(XFS_AGFL_MAGIC);
+                        agfl->agfl_seqno = cpu_to_be32(agno);
+                        uuid_copy(&agfl->agfl_uuid, &mp->m_sb.sb_uuid);
+                }
                 for (bucket = 0; bucket < XFS_AGFL_SIZE(mp); bucket++)
                         agfl->agfl_bno[bucket] = cpu_to_be32(NULLAGBLOCK);