[Ocfs2-devel] [patch 25/25] ocfs2/dlm: move lock to the tail of grant queue while doing in-place convert

[Joseph Qi <joseph.qi@huawei.com>]

On 2016/3/24 4:12, akpm at linux-foundation.org wrote:
> From: xuejiufei <xuejiufei@huawei.com>
> Subject: ocfs2/dlm: move lock to the tail of grant queue while doing in-place convert
> 
> We have found a bug when two nodes doing umount one after another.
> 
> 1) Node 1 migrate a lockres that has 3 locks in grant queue such as
>    N2(PR)<->N3(NL)<->N4(PR) to N2.  After migration, lvb of the lock
>    N3(NL) and N4(PR) are empty on node 2 because migration target do not
>    copy lvb to these two lock.
> 
> 2) Node 3 want to convert to PR, it can be granted in
>    __dlmconvert_master(), and the order of these locks is unchanged.  The
>    lvb of the lock N3(PR) on node 2 is copyed from lockres in function
>    dlm_update_lvb() while the lvb of lock N4(PR) is still empty.
> 
> 3) Node 2 want to leave domain, it will migrate this lockres to node 3.
>    Then node 2 will trigger the BUG in dlm_prepare_lvb_for_migration()
>    when adding the lock N4(PR) to mres with the following message because
>    the lvb of mres is already copied from lock N3(PR), but the lvb of lock
>    N4(PR) is empty.
> 
> "Mismatched lvb in lock cookie=%u:%llu, name=%.*s, node=%u"
> 
> [akpm at linux-foundation.org: tweak comment]
> Signed-off-by: xuejiufei <xuejiufei@huawei.com>
Acked-by: Joseph Qi <joseph.qi@huawei.com>

> Cc: Mark Fasheh <mfasheh@suse.de>
> Cc: Joel Becker <jlbec@evilplan.org>
> Cc: Junxiao Bi <junxiao.bi@oracle.com>
> Cc: Joseph Qi <joseph.qi@huawei.com>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> ---
> 
>  fs/ocfs2/dlm/dlmconvert.c |    6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff -puN fs/ocfs2/dlm/dlmconvert.c~ocfs2-dlm-move-lock-to-the-tail-of-grant-queue-while-doing-in-place-convert fs/ocfs2/dlm/dlmconvert.c
> --- a/fs/ocfs2/dlm/dlmconvert.c~ocfs2-dlm-move-lock-to-the-tail-of-grant-queue-while-doing-in-place-convert
> +++ a/fs/ocfs2/dlm/dlmconvert.c
> @@ -212,6 +212,12 @@ grant:
>  	if (lock->lksb->flags & DLM_LKSB_PUT_LVB)
>  		memcpy(res->lvb, lock->lksb->lvb, DLM_LVB_LEN);
>  
> +	/*
> +	 * Move the lock to the tail because it may be the only lock which has
> +	 * an invalid lvb.
> +	 */
> +	list_move_tail(&lock->list, &res->granted);
> +
>  	status = DLM_NORMAL;
>  	*call_ast = 1;
>  	goto unlock_exit;
> _
> 
> .
>