[Cluster-devel] GFS2: Fix one RG corner case

[Bob Peterson <rpeterso@redhat.com>]

----- Original Message -----
| >From aa8920c96897dd82f0520f9e7db7311b42547ce6 Mon Sep 17 00:00:00
| >2001
| From: Steven Whitehouse <swhiteho@redhat.com>
| Date: Tue, 13 Nov 2012 14:50:35 +0000
| Subject: GFS2: Fix one RG corner case
| 
| For filesystems with only a single resource group, we need to be
| careful
| that the allocation loop will not land up with a NULL resource group.
| This
| fixes a bug in a previous patch where the gfs2_rgrpd_get_next()
| function
| was being used instead of gfs2_rgrpd_get_first()
| 
| Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
| 
| diff --git a/fs/gfs2/rgrp.c b/fs/gfs2/rgrp.c
| index 99a6197..5625e93 100644
| --- a/fs/gfs2/rgrp.c
| +++ b/fs/gfs2/rgrp.c
| @@ -1776,10 +1776,11 @@ static u32 gfs2_orlov_skip(const struct
| gfs2_inode *ip)
|  static bool gfs2_select_rgrp(struct gfs2_rgrpd **pos, const struct
|  gfs2_rgrpd *begin)
|  {
|  	struct gfs2_rgrpd *rgd = *pos;
| +	struct gfs2_sbd *sdp = rgd->rd_sbd;
|  
|  	rgd = gfs2_rgrpd_get_next(rgd);
|  	if (rgd == NULL)
| -		rgd = gfs2_rgrpd_get_next(NULL);
| +		rgd = gfs2_rgrpd_get_first(sdp);
|  	*pos = rgd;
|  	if (rgd != begin) /* If we didn't wrap */
|  		return true;
| --
| 1.7.4

Hi,

If we do this, can't we get into an infinite loop if the one and only
rgrp is full? In that case, rgrp will be == begin, so it won't return
true, so the caller won't ever realize it's wrapped.

Regards,

Bob Peterson
Red Hat File Systems