xfs: return inode fork offset in bulkstat for fsr

So that fsr can attempt to get the fork offset of the temporary
inode it uses the same as the inode it is defragmenting, pass the
fork offset out in the bulkstat information.

The bulkstat structure has padding that has always been zeroed, so
userspace can tell if this field is set or not by use of the xattr
present flag and a non-zero value for the fork offset.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alex Elder <aelder@sgi.com>

fs/xfs/xfs_fs.h

@@ -292,7 +292,8 @@ typedef struct xfs_bstat {
 	__s32		bs_extents;	/* number of extents		*/
 	__u32		bs_gen;		/* generation count		*/
 	__u16		bs_projid;	/* project id			*/
-	unsigned char	bs_pad[14];	/* pad space, unused		*/
+	__u16		bs_forkoff;	/* inode fork offset in bytes	*/
+	unsigned char	bs_pad[12];	/* pad space, unused		*/
 	__u32		bs_dmevmask;	/* DMIG event mask		*/
 	__u16		bs_dmstate;	/* DMIG state info		*/
 	__u16		bs_aextents;	/* attribute number of extents	*/

fs/xfs/xfs_itable.c

@@ -106,6 +106,7 @@ xfs_bulkstat_one_iget(
 	buf->bs_dmevmask = dic->di_dmevmask;
 	buf->bs_dmstate = dic->di_dmstate;
 	buf->bs_aextents = dic->di_anextents;
+	buf->bs_forkoff = XFS_IFORK_BOFF(ip);
 
 	switch (dic->di_format) {
 	case XFS_DINODE_FMT_DEV:
@@ -176,6 +177,7 @@ xfs_bulkstat_one_dinode(
 	buf->bs_dmevmask = be32_to_cpu(dic->di_dmevmask);
 	buf->bs_dmstate = be16_to_cpu(dic->di_dmstate);
 	buf->bs_aextents = be16_to_cpu(dic->di_anextents);
+	buf->bs_forkoff = XFS_DFORK_BOFF(dic);
 
 	switch (dic->di_format) {
 	case XFS_DINODE_FMT_DEV: