xfs: specify AG in bulk req

Add a new xfs_bulk_ireq flag to constrain the iteration to a single AG.
If the passed-in startino value is zero then we start with the first
inode in the AG that the user passes in; otherwise, we iterate only
within the same AG as the passed-in inode.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Allison Collins <allison.henderson@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
index ae7b743..e1e1d9d 100644
--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -844,7 +844,6 @@ xfs_bulk_ireq_setup(
 {
 	if (hdr->icount == 0 ||
 	    (hdr->flags & ~XFS_BULK_IREQ_FLAGS_ALL) ||
-	    hdr->reserved32 ||
 	    memchr_inv(hdr->reserved, 0, sizeof(hdr->reserved)))
 		return -EINVAL;
 
@@ -852,6 +851,29 @@ xfs_bulk_ireq_setup(
 	breq->ubuffer = ubuffer;
 	breq->icount = hdr->icount;
 	breq->ocount = 0;
+	breq->flags = 0;
+
+	/*
+	 * The IREQ_AGNO flag means that we only want results from a given AG.
+	 * If @hdr->ino is zero, we start iterating in that AG.  If @hdr->ino is
+	 * beyond the specified AG then we return no results.
+	 */
+	if (hdr->flags & XFS_BULK_IREQ_AGNO) {
+		if (hdr->agno >= mp->m_sb.sb_agcount)
+			return -EINVAL;
+
+		if (breq->startino == 0)
+			breq->startino = XFS_AGINO_TO_INO(mp, hdr->agno, 0);
+		else if (XFS_INO_TO_AGNO(mp, breq->startino) < hdr->agno)
+			return -EINVAL;
+
+		breq->flags |= XFS_IBULK_SAME_AG;
+
+		/* Asking for an inode past the end of the AG?  We're done! */
+		if (XFS_INO_TO_AGNO(mp, breq->startino) > hdr->agno)
+			return XFS_ITER_ABORT;
+	} else if (hdr->agno)
+		return -EINVAL;
 
 	/* Asking for an inode past the end of the FS?  We're done! */
 	if (XFS_INO_TO_AGNO(mp, breq->startino) >= mp->m_sb.sb_agcount)