[Cluster-devel] [PATCH 5 of 5] Bz #248176: GFS2: invalid metadata block - REVISED
Wendy Cheng
wcheng at redhat.com
Thu Aug 9 19:07:38 UTC 2007
Bob Peterson wrote:
> The problem was that the journal inodes, although protected by
> a glock, were not synched with the other nodes because they don't
> use the inode glock synch operations (i.e. no "glops" were defined).
> Therefore, journal recovery on a journal-recovering node were causing
> the blocks to get out of sync with the node that was actually trying
> to use that journal as it comes back up from a reboot.
>
I don't understand this patch either. Maybe I have worked too long in
GFS1 so please educate me on these GFS2 internals. Comment below:
> There are two possible solutions: (1) To make the journals use the
> normal inode glock sync operations, or (2) To make the journal
> operations take effect immediately (i.e. no caching). Although
> option 1 works, it turns out to be a lot more code. Steve opted
> for option 2, which is much simpler and therefore less prone to
> regression errors.
>
> Regards,
>
> Bob Peterson
> --
> Signed-off-by: Bob Peterson <rpeterso at redhat.com>
> --
> diff --git a/fs/gfs2/ops_fstype.c b/fs/gfs2/ops_fstype.c
> index 58c730b..f0bcaa2 100644
> --- a/fs/gfs2/ops_fstype.c
> +++ b/fs/gfs2/ops_fstype.c
> @@ -358,7 +358,7 @@ static int init_journal(struct gfs2_sbd *sdp, int undo)
>
> ip = GFS2_I(sdp->sd_jdesc->jd_inode);
> error = gfs2_glock_nq_init(ip->i_gl, LM_ST_SHARED,
> - LM_FLAG_NOEXP | GL_EXACT,
> + LM_FLAG_NOEXP | GL_EXACT | GL_NOCACHE,
> &sdp->sd_jinode_gh);
> if (error) {
> fs_err(sdp, "can't acquire journal inode glock: %d\n",
> diff --git a/fs/gfs2/recovery.c b/fs/gfs2/recovery.c
> index 5ada38c..beb6c7a 100644
> --- a/fs/gfs2/recovery.c
> +++ b/fs/gfs2/recovery.c
> @@ -469,7 +469,7 @@ int gfs2_recover_journal(struct gfs2_jdesc *jd)
> };
>
> error = gfs2_glock_nq_init(ip->i_gl, LM_ST_SHARED,
> - LM_FLAG_NOEXP, &ji_gh);
> + LM_FLAG_NOEXP | GL_NOCACHE, &ji_gh);
> if (error)
> goto fail_gunlock_j;
> } else {
>
>
This lock is requested as "SHARED" (read lock). So how does "GL_NOCACHE"
help it to "sync" with other nodes regarding to disk blocks sharing as
you described above ? For a normal EXCLUSIVE inode glock with nocache,
it will force a sync (disk blocks). However, this is a read lock. So
what is the problem this patch has solved ?
-- Wendy
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