Hi Andrew,
As discussed, this fix is better than mine.
So please discard mine (linux-next commit 71bd4edae86b) and take this,
thanks.
On 2015/4/30 22:24, Junxiao Bi wrote:
> There is a race window in dlm_get_lock_resource(), which may
> return a lock resource which have been purged. This will cause
> the process hung forever in dlmlock() as the ast msg can't be
> handled due to its lock resource not exist.
>
> dlm_get_lock_resource {
> ...
> spin_lock(&dlm->spinlock);
> tmpres = __dlm_lookup_lockres_full(dlm, lockid, namelen, hash);
> if (tmpres) {
> spin_unlock(&dlm->spinlock);
> >>>>>>>> race window, dlm_run_purge_list() may run and purge
> the lock resource
> spin_lock(&tmpres->spinlock);
> ...
> spin_unlock(&tmpres->spinlock);
> }
> }
>
> Signed-off-by: Junxiao Bi <junxiao...@oracle.com>
> Cc: Joseph Qi <joseph...@huawei.com>
> Cc: <sta...@vger.kernel.org>
> ---
> fs/ocfs2/dlm/dlmmaster.c | 13 +++++++++++++
> 1 file changed, 13 insertions(+)
>
> diff --git a/fs/ocfs2/dlm/dlmmaster.c b/fs/ocfs2/dlm/dlmmaster.c
> index a6944b2..fdf4b41 100644
> --- a/fs/ocfs2/dlm/dlmmaster.c
> +++ b/fs/ocfs2/dlm/dlmmaster.c
> @@ -757,6 +757,19 @@ lookup:
> if (tmpres) {
> spin_unlock(&dlm->spinlock);
> spin_lock(&tmpres->spinlock);
> +
> + /*
> + * Right after dlm spinlock was released, dlm_thread could have
> + * purged the lockres. Check if lockres got unhashed. If so
> + * start over.
> + */
> + if (hlist_unhashed(&tmpres->hash_node)) {
> + spin_unlock(&tmpres->spinlock);
> + dlm_lockres_put(tmpres);
> + tmpres = NULL;
> + goto lookup;
> + }
> +
> /* Wait on the thread that is mastering the resource */
> if (tmpres->owner == DLM_LOCK_RES_OWNER_UNKNOWN) {
> __dlm_wait_on_lockres(tmpres);
>
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