gfs2: Fix loop in gfs2_rbm_find

BugLink: https://bugs.launchpad.net/bugs/1811647

commit 2d29f6b9 upstream.

Fix the resource group wrap-around logic in gfs2_rbm_find that commit
e579ed4f broke.  The bug can lead to unnecessary repeated scanning of the
same bitmaps; there is a risk that future changes will turn this into an
endless loop.

Fixes: e579ed4f ("GFS2: Introduce rbm field bii")
Cc: stable@vger.kernel.org # v3.13+
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

fs/gfs2/rgrp.c

@@ -1720,9 +1720,9 @@ static int gfs2_rbm_find(struct gfs2_rbm *rbm, u8 state, u32 *minext,
 			goto next_iter;
 		}
 		if (ret == -E2BIG) {
+			n += rbm->bii - initial_bii;
 			rbm->bii = 0;
 			rbm->offset = 0;
-			n += (rbm->bii - initial_bii);
 			goto res_covered_end_of_rgrp;
 		}
 		return ret;