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, 23 insertions, 2 deletions

diff --git a/fs/xfs/xfs_ag.h b/fs/xfs/xfs_ag.h
index 9f4815e0c96f..272ef097e2be 100644
--- a/fs/xfs/xfs_ag.h
+++ b/fs/xfs/xfs_ag.h
@@ -30,6 +30,7 @@ struct xfs_trans;
 
 #define XFS_AGF_MAGIC   0x58414746      /* 'XAGF' */
 #define XFS_AGI_MAGIC   0x58414749      /* 'XAGI' */
+#define XFS_AGFL_MAGIC  0x5841464c      /* 'XAFL' */
 #define XFS_AGF_VERSION 1
 #define XFS_AGI_VERSION 1
 
@@ -190,11 +191,31 @@ extern const struct xfs_buf_ops xfs_agi_buf_ops;
  */
 #define XFS_AGFL_DADDR(mp)      ((xfs_daddr_t)(3 << (mp)->m_sectbb_log))
 #define XFS_AGFL_BLOCK(mp)      XFS_HDR_BLOCK(mp, XFS_AGFL_DADDR(mp))
-#define XFS_AGFL_SIZE(mp)       ((mp)->m_sb.sb_sectsize / sizeof(xfs_agblock_t))
 #define XFS_BUF_TO_AGFL(bp)     ((xfs_agfl_t *)((bp)->b_addr))
 
+#define XFS_BUF_TO_AGFL_BNO(mp, bp) \
+        (xfs_sb_version_hascrc(&((mp)->m_sb)) ? \
+                &(XFS_BUF_TO_AGFL(bp)->agfl_bno[0]) : \
+                (__be32 *)(bp)->b_addr)
+
+/*
+ * Size of the AGFL.  For CRC-enabled filesystes we steal a couple of
+ * slots in the beginning of the block for a proper header with the
+ * location information and CRC.
+ */
+#define XFS_AGFL_SIZE(mp) \
+        (((mp)->m_sb.sb_sectsize - \
+         (xfs_sb_version_hascrc(&((mp)->m_sb)) ? \
+                sizeof(struct xfs_agfl) : 0)) / \
+          sizeof(xfs_agblock_t))
+
 typedef struct xfs_agfl {
-        __be32          agfl_bno[1];    /* actually XFS_AGFL_SIZE(mp) */
+        __be32          agfl_magicnum;
+        __be32          agfl_seqno;
+        uuid_t          agfl_uuid;
+        __be64          agfl_lsn;
+        __be32          agfl_crc;
+        __be32          agfl_bno[];     /* actually XFS_AGFL_SIZE(mp) */
 } xfs_agfl_t;
 
 /*