gfs2: Don't search for unreserved space twice

If gfs2_inplace_reserve has chosen a resource group but it couldn't make a
reservation there, there are too many other reservations in that resource
group.  In that case, don't even try to respect existing reservations in
gfs2_alloc_blocks.
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

fs/gfs2/rgrp.c

@@ -2384,11 +2384,12 @@ int gfs2_alloc_blocks(struct gfs2_inode *ip, u64 *bn, unsigned int *nblocks,
 	struct gfs2_rbm rbm = { .rgd = ip->i_res.rs_rgd, };
 	u64 block; /* block, within the file system scope */
 	u32 minext = 1;
-	int error;
-
-	gfs2_set_alloc_start(&rbm, ip, dinode);
-	error = gfs2_rbm_find(&rbm, GFS2_BLKST_FREE, &minext, &ip->i_res, false);
+	int error = -ENOSPC;
 
+	if (gfs2_rs_active(&ip->i_res)) {
+		gfs2_set_alloc_start(&rbm, ip, dinode);
+		error = gfs2_rbm_find(&rbm, GFS2_BLKST_FREE, &minext, &ip->i_res, false);
+	}
 	if (error == -ENOSPC) {
 		gfs2_set_alloc_start(&rbm, ip, dinode);
 		error = gfs2_rbm_find(&rbm, GFS2_BLKST_FREE, &minext, NULL, false);