[Ocfs2-devel] [PATCH] ocfs2/dlm: avoid incorrect bit set in refmap on recovery master
Srinivas Eeda
srinivas.eeda at oracle.com
Fri Jul 23 15:27:36 PDT 2010
thanks for making this patch, it looks good just few minor changes about
comments
On 7/23/2010 5:15 AM, Wengang Wang wrote:
> In the following situation, there remains an incorrect bit in refmap on the
> recovery master. Finally the recovery master will fail at purging the lockres
> due to the incorrect bit in refmap.
>
> 1) node A has no interest on lockres A any longer, so it is purging it.
> 2) the owner of lockres A is node B, so node A is sending de-ref message
> to node B.
> 3) at this time, node B crashed. node C becomes the recovery master. it recovers
> lockres A(because the master is the dead node B).
> 4) node A migrated lockres A to node C with a refbit there.
> 5) node A failed to send de-ref message to node B because it crashed. The failure
> is ignored. no other action is done for lockres A any more.
>
> For mormal, re-send the deref message to it to recovery master can fix it. Well,
> ignoring the failure of deref to the original master and not recovering the lockres
> to recovery master has the same effect. And the later is simpler.
>
> Signed-off-by: Wengang Wang <wen.gang.wang at oracle.com>
> ---
> fs/ocfs2/dlm/dlmrecovery.c | 17 +++++++++++++++--
> fs/ocfs2/dlm/dlmthread.c | 28 +++++++++++++++++-----------
> 2 files changed, 32 insertions(+), 13 deletions(-)
>
> diff --git a/fs/ocfs2/dlm/dlmrecovery.c b/fs/ocfs2/dlm/dlmrecovery.c
> index 9dfaac7..06640f6 100644
> --- a/fs/ocfs2/dlm/dlmrecovery.c
> +++ b/fs/ocfs2/dlm/dlmrecovery.c
> @@ -1997,6 +1997,8 @@ void dlm_move_lockres_to_recovery_list(struct dlm_ctxt *dlm,
> struct list_head *queue;
> struct dlm_lock *lock, *next;
>
> + assert_spin_locked(&dlm->spinlock);
> + assert_spin_locked(&res->spinlock);
> res->state |= DLM_LOCK_RES_RECOVERING;
> if (!list_empty(&res->recovering)) {
> mlog(0,
> @@ -2336,9 +2338,20 @@ static void dlm_do_local_recovery_cleanup(struct dlm_ctxt *dlm, u8 dead_node)
>
> /* the wake_up for this will happen when the
> * RECOVERING flag is dropped later */
>
remove above comment as it doesn't seem to be relevant anymore.
> - res->state &= ~DLM_LOCK_RES_DROPPING_REF;
> + if (res->state & DLM_LOCK_RES_DROPPING_REF) {
> + /*
> + * don't migrate a lockres which is in
> + * progress of dropping ref
> + */
>
move this comment to before the if condition
> + mlog(ML_NOTICE, "%.*s ignored for "
> + "migration\n", res->lockname.len,
> + res->lockname.name);
>
This information only helps us in diagnosing any related issue and is
not helpful in normal cases. So it should be 0 instead of ML_NOTICE.
> + res->state &=
> + ~DLM_LOCK_RES_DROPPING_REF;
>
we don't need to clear this state as dlm_purge_lockres removes it.
> + } else
> + dlm_move_lockres_to_recovery_list(dlm,
> + res);
>
> - dlm_move_lockres_to_recovery_list(dlm, res);
> } else if (res->owner == dlm->node_num) {
> dlm_free_dead_locks(dlm, res, dead_node);
> __dlm_lockres_calc_usage(dlm, res);
> diff --git a/fs/ocfs2/dlm/dlmthread.c b/fs/ocfs2/dlm/dlmthread.c
> index dd78ca3..47420ce 100644
> --- a/fs/ocfs2/dlm/dlmthread.c
> +++ b/fs/ocfs2/dlm/dlmthread.c
> @@ -92,17 +92,23 @@ int __dlm_lockres_has_locks(struct dlm_lock_resource *res)
> * truly ready to be freed. */
> int __dlm_lockres_unused(struct dlm_lock_resource *res)
> {
> - if (!__dlm_lockres_has_locks(res) &&
> - (list_empty(&res->dirty) && !(res->state & DLM_LOCK_RES_DIRTY))) {
> - /* try not to scan the bitmap unless the first two
> - * conditions are already true */
> - int bit = find_next_bit(res->refmap, O2NM_MAX_NODES, 0);
> - if (bit >= O2NM_MAX_NODES) {
> - /* since the bit for dlm->node_num is not
> - * set, inflight_locks better be zero */
> - BUG_ON(res->inflight_locks != 0);
> - return 1;
> - }
> + int bit;
> +
> + if (__dlm_lockres_has_locks(res))
> + return 0;
> +
> + if (!list_empty(&res->dirty) || res->state & DLM_LOCK_RES_DIRTY)
> + return 0;
> +
> + if (res->state & DLM_LOCK_RES_RECOVERING)
> + return 0;
> +
> + bit = find_next_bit(res->refmap, O2NM_MAX_NODES, 0);
> + if (bit >= O2NM_MAX_NODES) {
> + /* since the bit for dlm->node_num is not
> + * set, inflight_locks better be zero */
> + BUG_ON(res->inflight_locks != 0);
> + return 1;
> }
> return 0;
> }
>
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