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![David Teigland](/assets/img/avatar_default.png)
Introduce a per-lockspace rwsem that's held in read mode by dlm_recv threads while working in the dlm. This allows dlm_recv activity to be suspended when the lockspace transitions to, from and between recovery cycles. The specific bug prompting this change is one where an in-progress recovery cycle is aborted by a new recovery cycle. While dlm_recv was processing a recovery message, the recovery cycle was aborted and dlm_recoverd began cleaning up. dlm_recv decremented recover_locks_count on an rsb after dlm_recoverd had reset it to zero. This is fixed by suspending dlm_recv (taking write lock on the rwsem) before aborting the current recovery. The transitions to/from normal and recovery modes are simplified by using this new ability to block dlm_recv. The switch from normal to recovery mode means dlm_recv goes from processing locking messages, to saving them for later, and vice versa. Races are avoided by blocking dlm_recv when setting the flag that switches between modes. Signed-off-by: David Teigland <teigland@redhat.com> Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
188 lines
5.2 KiB
C
188 lines
5.2 KiB
C
/******************************************************************************
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*******************************************************************************
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**
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** Copyright (C) 2005-2007 Red Hat, Inc. All rights reserved.
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**
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** This copyrighted material is made available to anyone wishing to use,
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** modify, copy, or redistribute it subject to the terms and conditions
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** of the GNU General Public License v.2.
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**
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*******************************************************************************
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******************************************************************************/
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#include "dlm_internal.h"
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#include "member.h"
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#include "lock.h"
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#include "dir.h"
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#include "config.h"
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#include "requestqueue.h"
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struct rq_entry {
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struct list_head list;
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int nodeid;
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char request[0];
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};
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/*
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* Requests received while the lockspace is in recovery get added to the
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* request queue and processed when recovery is complete. This happens when
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* the lockspace is suspended on some nodes before it is on others, or the
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* lockspace is enabled on some while still suspended on others.
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*/
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void dlm_add_requestqueue(struct dlm_ls *ls, int nodeid, struct dlm_header *hd)
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{
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struct rq_entry *e;
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int length = hd->h_length;
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e = kmalloc(sizeof(struct rq_entry) + length, GFP_KERNEL);
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if (!e) {
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log_print("dlm_add_requestqueue: out of memory len %d", length);
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return;
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}
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e->nodeid = nodeid;
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memcpy(e->request, hd, length);
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mutex_lock(&ls->ls_requestqueue_mutex);
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list_add_tail(&e->list, &ls->ls_requestqueue);
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mutex_unlock(&ls->ls_requestqueue_mutex);
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}
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/*
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* Called by dlm_recoverd to process normal messages saved while recovery was
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* happening. Normal locking has been enabled before this is called. dlm_recv
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* upon receiving a message, will wait for all saved messages to be drained
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* here before processing the message it got. If a new dlm_ls_stop() arrives
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* while we're processing these saved messages, it may block trying to suspend
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* dlm_recv if dlm_recv is waiting for us in dlm_wait_requestqueue. In that
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* case, we don't abort since locking_stopped is still 0. If dlm_recv is not
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* waiting for us, then this processing may be aborted due to locking_stopped.
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*/
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int dlm_process_requestqueue(struct dlm_ls *ls)
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{
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struct rq_entry *e;
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int error = 0;
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mutex_lock(&ls->ls_requestqueue_mutex);
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for (;;) {
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if (list_empty(&ls->ls_requestqueue)) {
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mutex_unlock(&ls->ls_requestqueue_mutex);
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error = 0;
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break;
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}
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e = list_entry(ls->ls_requestqueue.next, struct rq_entry, list);
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mutex_unlock(&ls->ls_requestqueue_mutex);
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dlm_receive_message_saved(ls, (struct dlm_message *)e->request);
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mutex_lock(&ls->ls_requestqueue_mutex);
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list_del(&e->list);
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kfree(e);
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if (dlm_locking_stopped(ls)) {
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log_debug(ls, "process_requestqueue abort running");
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mutex_unlock(&ls->ls_requestqueue_mutex);
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error = -EINTR;
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break;
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}
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schedule();
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}
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return error;
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}
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/*
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* After recovery is done, locking is resumed and dlm_recoverd takes all the
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* saved requests and processes them as they would have been by dlm_recv. At
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* the same time, dlm_recv will start receiving new requests from remote nodes.
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* We want to delay dlm_recv processing new requests until dlm_recoverd has
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* finished processing the old saved requests. We don't check for locking
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* stopped here because dlm_ls_stop won't stop locking until it's suspended us
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* (dlm_recv).
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*/
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void dlm_wait_requestqueue(struct dlm_ls *ls)
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{
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for (;;) {
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mutex_lock(&ls->ls_requestqueue_mutex);
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if (list_empty(&ls->ls_requestqueue))
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break;
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mutex_unlock(&ls->ls_requestqueue_mutex);
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schedule();
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}
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mutex_unlock(&ls->ls_requestqueue_mutex);
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}
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static int purge_request(struct dlm_ls *ls, struct dlm_message *ms, int nodeid)
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{
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uint32_t type = ms->m_type;
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/* the ls is being cleaned up and freed by release_lockspace */
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if (!ls->ls_count)
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return 1;
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if (dlm_is_removed(ls, nodeid))
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return 1;
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/* directory operations are always purged because the directory is
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always rebuilt during recovery and the lookups resent */
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if (type == DLM_MSG_REMOVE ||
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type == DLM_MSG_LOOKUP ||
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type == DLM_MSG_LOOKUP_REPLY)
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return 1;
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if (!dlm_no_directory(ls))
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return 0;
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/* with no directory, the master is likely to change as a part of
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recovery; requests to/from the defunct master need to be purged */
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switch (type) {
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case DLM_MSG_REQUEST:
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case DLM_MSG_CONVERT:
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case DLM_MSG_UNLOCK:
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case DLM_MSG_CANCEL:
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/* we're no longer the master of this resource, the sender
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will resend to the new master (see waiter_needs_recovery) */
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if (dlm_hash2nodeid(ls, ms->m_hash) != dlm_our_nodeid())
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return 1;
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break;
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case DLM_MSG_REQUEST_REPLY:
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case DLM_MSG_CONVERT_REPLY:
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case DLM_MSG_UNLOCK_REPLY:
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case DLM_MSG_CANCEL_REPLY:
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case DLM_MSG_GRANT:
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/* this reply is from the former master of the resource,
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we'll resend to the new master if needed */
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if (dlm_hash2nodeid(ls, ms->m_hash) != nodeid)
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return 1;
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break;
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}
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return 0;
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}
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void dlm_purge_requestqueue(struct dlm_ls *ls)
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{
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struct dlm_message *ms;
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struct rq_entry *e, *safe;
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mutex_lock(&ls->ls_requestqueue_mutex);
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list_for_each_entry_safe(e, safe, &ls->ls_requestqueue, list) {
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ms = (struct dlm_message *) e->request;
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if (purge_request(ls, ms, e->nodeid)) {
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list_del(&e->list);
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kfree(e);
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}
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}
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mutex_unlock(&ls->ls_requestqueue_mutex);
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}
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