[XFS] factor out xfs_read_agi helper

Add a helper to read the AGI header and perform basic verification.
Based on hunks from a larger patch from Dave Chinner.

(First sent on Juli 23rd)

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <david@fromorbit.com>
Signed-off-by: Niv Sardi <xaiki@sgi.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/fs/xfs/xfs_ag.h b/fs/xfs/xfs_ag.h
index 2bfd86329141..f4a315390c61 100644
--- a/fs/xfs/xfs_ag.h
+++ b/fs/xfs/xfs_ag.h
@@ -142,6 +142,9 @@ typedef struct xfs_agi {
 #define XFS_AGI_BLOCK(mp)       XFS_HDR_BLOCK(mp, XFS_AGI_DADDR(mp))
 #define XFS_BUF_TO_AGI(bp)      ((xfs_agi_t *)XFS_BUF_PTR(bp))
 
+extern int xfs_read_agi(struct xfs_mount *mp, struct xfs_trans *tp,
+                                xfs_agnumber_t agno, struct xfs_buf **bpp);
+
 /*
  * The third a.g. block contains the a.g. freelist, an array
  * of block pointers to blocks owned by the allocation btree code.