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[DLM] block dlm_recv in recovery transition

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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>
This commit is contained in:
David Teigland
2007-09-27 15:53:38 -05:00
committed by Steven Whitehouse
parent b434eda6fd
commit c36258b592
11 changed files with 161 additions and 152 deletions
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58
fs/dlm/requestqueue.c
View File

@@ -1,7 +1,7 @@
/******************************************************************************
*******************************************************************************
**
** Copyright (C) 2005 Red Hat, Inc. All rights reserved.
** Copyright (C) 2005-2007 Red Hat, Inc. All rights reserved.
**
** This copyrighted material is made available to anyone wishing to use,
** modify, copy, or redistribute it subject to the terms and conditions
@@ -20,7 +20,7 @@
struct rq_entry {
struct list_head list;
int nodeid;
char request[1];
char request[0];
};
/*
@@ -30,42 +30,39 @@ struct rq_entry {
* lockspace is enabled on some while still suspended on others.
*/
int dlm_add_requestqueue(struct dlm_ls *ls, int nodeid, struct dlm_header *hd)
void dlm_add_requestqueue(struct dlm_ls *ls, int nodeid, struct dlm_header *hd)
{
struct rq_entry *e;
int length = hd->h_length;
int rv = 0;
e = kmalloc(sizeof(struct rq_entry) + length, GFP_KERNEL);
if (!e) {
log_print("dlm_add_requestqueue: out of memory\n");
return 0;
log_print("dlm_add_requestqueue: out of memory len %d", length);
return;
}
e->nodeid = nodeid;
memcpy(e->request, hd, length);
/* We need to check dlm_locking_stopped() after taking the mutex to
avoid a race where dlm_recoverd enables locking and runs
process_requestqueue between our earlier dlm_locking_stopped check
and this addition to the requestqueue. */
mutex_lock(&ls->ls_requestqueue_mutex);
if (dlm_locking_stopped(ls))
list_add_tail(&e->list, &ls->ls_requestqueue);
else {
log_debug(ls, "dlm_add_requestqueue skip from %d", nodeid);
kfree(e);
rv = -EAGAIN;
}
list_add_tail(&e->list, &ls->ls_requestqueue);
mutex_unlock(&ls->ls_requestqueue_mutex);
return rv;
}
/*
* Called by dlm_recoverd to process normal messages saved while recovery was
* happening. Normal locking has been enabled before this is called. dlm_recv
* upon receiving a message, will wait for all saved messages to be drained
* here before processing the message it got. If a new dlm_ls_stop() arrives
* while we're processing these saved messages, it may block trying to suspend
* dlm_recv if dlm_recv is waiting for us in dlm_wait_requestqueue. In that
* case, we don't abort since locking_stopped is still 0. If dlm_recv is not
* waiting for us, then this processing may be aborted due to locking_stopped.
*/
int dlm_process_requestqueue(struct dlm_ls *ls)
{
struct rq_entry *e;
struct dlm_header *hd;
int error = 0;
mutex_lock(&ls->ls_requestqueue_mutex);
@@ -79,14 +76,7 @@ int dlm_process_requestqueue(struct dlm_ls *ls)
e = list_entry(ls->ls_requestqueue.next, struct rq_entry, list);
mutex_unlock(&ls->ls_requestqueue_mutex);
hd = (struct dlm_header *) e->request;
error = dlm_receive_message(hd, e->nodeid, 1);
if (error == -EINTR) {
/* entry is left on requestqueue */
log_debug(ls, "process_requestqueue abort eintr");
break;
}
dlm_receive_message_saved(ls, (struct dlm_message *)e->request);
mutex_lock(&ls->ls_requestqueue_mutex);
list_del(&e->list);
@@ -106,10 +96,12 @@ int dlm_process_requestqueue(struct dlm_ls *ls)
/*
* After recovery is done, locking is resumed and dlm_recoverd takes all the
* saved requests and processes them as they would have been by dlm_recvd. At
* the same time, dlm_recvd will start receiving new requests from remote
* nodes. We want to delay dlm_recvd processing new requests until
* dlm_recoverd has finished processing the old saved requests.
* saved requests and processes them as they would have been by dlm_recv. At
* the same time, dlm_recv will start receiving new requests from remote nodes.
* We want to delay dlm_recv processing new requests until dlm_recoverd has
* finished processing the old saved requests. We don't check for locking
* stopped here because dlm_ls_stop won't stop locking until it's suspended us
* (dlm_recv).
*/
void dlm_wait_requestqueue(struct dlm_ls *ls)
@@ -118,8 +110,6 @@ void dlm_wait_requestqueue(struct dlm_ls *ls)
mutex_lock(&ls->ls_requestqueue_mutex);
if (list_empty(&ls->ls_requestqueue))
break;
if (dlm_locking_stopped(ls))
break;
mutex_unlock(&ls->ls_requestqueue_mutex);
schedule();
}