xfs: improve the code that checks recovered bmap intent items

The code that validates recovered bmap intent items is kind of a mess --
it doesn't use the standard xfs type validators, and it doesn't check
for things that it should.  Fix the validator function to use the
standard validation helpers and look for more types of obvious errors.
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>

fs/xfs/xfs_bmap_item.c

@@ -424,18 +424,12 @@ xfs_bui_validate(
 	struct xfs_bui_log_item		*buip)
 {
 	struct xfs_map_extent		*bmap;
-	xfs_fsblock_t			startblock_fsb;
-	xfs_fsblock_t			inode_fsb;
 
 	/* Only one mapping operation per BUI... */
 	if (buip->bui_format.bui_nextents != XFS_BUI_MAX_FAST_EXTENTS)
 		return false;
 
 	bmap = &buip->bui_format.bui_extents[0];
-	startblock_fsb = XFS_BB_TO_FSB(mp,
-			XFS_FSB_TO_DADDR(mp, bmap->me_startblock));
-	inode_fsb = XFS_BB_TO_FSB(mp, XFS_FSB_TO_DADDR(mp,
-			XFS_INO_TO_FSB(mp, bmap->me_owner)));
 
 	if (bmap->me_flags & ~XFS_BMAP_EXTENT_FLAGS)
 		return false;
@@ -448,13 +442,19 @@ xfs_bui_validate(
 		return false;
 	}
 
-	if (startblock_fsb == 0 ||
-	    bmap->me_len == 0 ||
-	    inode_fsb == 0 ||
-	    startblock_fsb >= mp->m_sb.sb_dblocks ||
-	    bmap->me_len >= mp->m_sb.sb_agblocks ||
-	    inode_fsb >= mp->m_sb.sb_dblocks ||
-	    (bmap->me_flags & ~XFS_BMAP_EXTENT_FLAGS))
+	if (!xfs_verify_ino(mp, bmap->me_owner))
+		return false;
+
+	if (bmap->me_startoff + bmap->me_len <= bmap->me_startoff)
+		return false;
+
+	if (bmap->me_startblock + bmap->me_len <= bmap->me_startblock)
+		return false;
+
+	if (!xfs_verify_fsbno(mp, bmap->me_startblock))
+		return false;
+
+	if (!xfs_verify_fsbno(mp, bmap->me_startblock + bmap->me_len - 1))
 		return false;
 
 	return true;