xfs: check on-disk (not incore) btree root size in dfrag.c

xfs_swap_extents_check_format() contains checks to make sure that
original and the temporary files during defrag are compatible;
Gabriel VLASIU ran into a case where xfs_fsr returned EINVAL
because the tests found the btree root to be of size 120,
while the fork offset was only 104; IOW, they overlapped.

However, this is just due to an error in the
xfs_swap_extents_check_format() tests, because it is checking
the in-memory btree root size against the on-disk fork offset.
We should be checking the on-disk sizes in both cases.

This patch adds a new macro to calculate this size, and uses
it in the tests.

With this change, the filesystem image provided by Gabriel
allows for proper file degragmentation.
Reported-by: Gabriel VLASIU <gabriel@vlasiu.net>
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

fs/xfs/xfs_bmap_btree.h

@@ -196,6 +196,8 @@ typedef __be64 xfs_bmbt_ptr_t, xfs_bmdr_ptr_t;
 #define XFS_BMDR_SPACE_CALC(nrecs) \
 	(int)(sizeof(xfs_bmdr_block_t) + \
 	       ((nrecs) * (sizeof(xfs_bmbt_key_t) + sizeof(xfs_bmbt_ptr_t))))
+#define XFS_BMAP_BMDR_SPACE(bb) \
+	(XFS_BMDR_SPACE_CALC(be16_to_cpu((bb)->bb_numrecs)))
 
 /*
  * Maximum number of bmap btree levels.

fs/xfs/xfs_dfrag.c

@@ -24,6 +24,9 @@
 #include "xfs_ag.h"
 #include "xfs_mount.h"
 #include "xfs_bmap_btree.h"
+#include "xfs_alloc_btree.h"
+#include "xfs_ialloc_btree.h"
+#include "xfs_btree.h"
 #include "xfs_dinode.h"
 #include "xfs_inode.h"
 #include "xfs_inode_item.h"
@@ -182,7 +185,7 @@ xfs_swap_extents_check_format(
 	 */
 	if (tip->i_d.di_format == XFS_DINODE_FMT_BTREE) {
 		if (XFS_IFORK_BOFF(ip) &&
-		    tip->i_df.if_broot_bytes > XFS_IFORK_BOFF(ip))
+		    XFS_BMAP_BMDR_SPACE(tip->i_df.if_broot) > XFS_IFORK_BOFF(ip))
 			return EINVAL;
 		if (XFS_IFORK_NEXTENTS(tip, XFS_DATA_FORK) <=
 		    XFS_IFORK_MAXEXT(ip, XFS_DATA_FORK))
@@ -192,9 +195,8 @@ xfs_swap_extents_check_format(
 	/* Reciprocal target->temp btree format checks */
 	if (ip->i_d.di_format == XFS_DINODE_FMT_BTREE) {
 		if (XFS_IFORK_BOFF(tip) &&
-		    ip->i_df.if_broot_bytes > XFS_IFORK_BOFF(tip))
+		    XFS_BMAP_BMDR_SPACE(ip->i_df.if_broot) > XFS_IFORK_BOFF(tip))
 			return EINVAL;
-
 		if (XFS_IFORK_NEXTENTS(ip, XFS_DATA_FORK) <=
 		    XFS_IFORK_MAXEXT(tip, XFS_DATA_FORK))
 			return EINVAL;