gfs2: Re-enable fallocate for the rindex

Commit 86066914edff2316cbed63aac8a87d5001441a16 "gfs2: Don't support
fallocate on jdata files" removed the ability of gfs2_grow to reserve
space at the end of the rindex, which could prevent a second gfs2_grow
from succeeding if the fs is full. Allow fallocate to work on the rindex
once again.

Signed-off-by: Andrew Price <anprice@redhat.com>
Signed-off-by: Bob Peterson <rpeterso@redhat.com>

fs/gfs2/file.c

@@ -911,11 +911,15 @@ out_qunlock:
 static long gfs2_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
 {
 	struct inode *inode = file_inode(file);
+	struct gfs2_sbd *sdp = GFS2_SB(inode);
 	struct gfs2_inode *ip = GFS2_I(inode);
 	struct gfs2_holder gh;
 	int ret;
 
-	if ((mode & ~FALLOC_FL_KEEP_SIZE) || gfs2_is_jdata(ip))
+	if (mode & ~FALLOC_FL_KEEP_SIZE)
+		return -EOPNOTSUPP;
+	/* fallocate is needed by gfs2_grow to reserve space in the rindex */
+	if (gfs2_is_jdata(ip) && inode != sdp->sd_rindex)
 		return -EOPNOTSUPP;
 
 	inode_lock(inode);