[PATCH 51/51] [DLM] block dlm_recv in recovery transition

swhiteho
2007-10-04T09:37:03Z

From: David Teigland <teigland@redhat.com>

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>

diff --git a/fs/dlm/dlm_internal.h b/fs/dlm/dlm_internal.h
index 74901e9..d2fc238 100644
--- a/fs/dlm/dlm_internal.h
+++ b/fs/dlm/dlm_internal.h
@@ -491,6 +491,7 @@ struct dlm_ls {
uint64_t ls_recover_seq;
struct dlm_recover *ls_recover_args;
struct rw_semaphore ls_in_recovery; /* block local requests */
+ struct rw_semaphore ls_recv_active; /* block dlm_recv */
struct list_head ls_requestqueue;/* queue remote requests */
struct mutex ls_requestqueue_mutex;
char *ls_recover_buf;
diff --git a/fs/dlm/lock.c b/fs/dlm/lock.c
index 031229f..3915b8e 100644
--- a/fs/dlm/lock.c
+++ b/fs/dlm/lock.c
@@ -3638,55 +3638,8 @@ static void receive_lookup_reply(struct dlm_ls *ls, struct dlm_message *ms)
dlm_put_lkb(lkb);
}

-int dlm_receive_message(struct dlm_header *hd, int nodeid, int recovery)
+static void _receive_message(struct dlm_ls *ls, struct dlm_message *ms)
{
- struct dlm_message *ms = (struct dlm_message *) hd;
- struct dlm_ls *ls;
- int error = 0;
-
- if (!recovery)
- dlm_message_in(ms);
-
- ls = dlm_find_lockspace_global(hd->h_lockspace);
- if (!ls) {
- log_print("drop message %d from %d for unknown lockspace %d",
- ms->m_type, nodeid, hd->h_lockspace);
- return -EINVAL;
- }
-
- /* recovery may have just ended leaving a bunch of backed-up requests
- in the requestqueue; wait while dlm_recoverd clears them */
-
- if (!recovery)
- dlm_wait_requestqueue(ls);
-
- /* recovery may have just started while there were a bunch of
- in-flight requests -- save them in requestqueue to be processed
- after recovery. we can't let dlm_recvd block on the recovery
- lock. if dlm_recoverd is calling this function to clear the
- requestqueue, it needs to be interrupted (-EINTR) if another
- recovery operation is starting. */
-
- while (1) {
- if (dlm_locking_stopped(ls)) {
- if (recovery) {
- error = -EINTR;
- goto out;
- }
- error = dlm_add_requestqueue(ls, nodeid, hd);
- if (error == -EAGAIN)
- continue;
- else {
- error = -EINTR;
- goto out;
- }
- }
-
- if (dlm_lock_recovery_try(ls))
- break;
- schedule();
- }
-
switch (ms->m_type) {

/* messages sent to a master node */
@@ -3761,17 +3714,90 @@ int dlm_receive_message(struct dlm_header *hd, int nodeid, int recovery)
log_error(ls, "unknown message type %d", ms->m_type);
}

- dlm_unlock_recovery(ls);
- out:
- dlm_put_lockspace(ls);
dlm_astd_wake();
- return error;
}

+/* If the lockspace is in recovery mode (locking stopped), then normal
+ messages are saved on the requestqueue for processing after recovery is
+ done. When not in recovery mode, we wait for dlm_recoverd to drain saved
+ messages off the requestqueue before we process new ones. This occurs right
+ after recovery completes when we transition from saving all messages on
+ requestqueue, to processing all the saved messages, to processing new
+ messages as they arrive. */

-/*
- * Recovery related
- */
+static void dlm_receive_message(struct dlm_ls *ls, struct dlm_message *ms,
+ int nodeid)
+{
+ if (dlm_locking_stopped(ls)) {
+ dlm_add_requestqueue(ls, nodeid, (struct dlm_header *) ms);
+ } else {
+ dlm_wait_requestqueue(ls);
+ _receive_message(ls, ms);
+ }
+}
+
+/* This is called by dlm_recoverd to process messages that were saved on
+ the requestqueue. */
+
+void dlm_receive_message_saved(struct dlm_ls *ls, struct dlm_message *ms)
+{
+ _receive_message(ls, ms);
+}
+
+/* This is called by the midcomms layer when something is received for
+ the lockspace. It could be either a MSG (normal message sent as part of
+ standard locking activity) or an RCOM (recovery message sent as part of
+ lockspace recovery). */
+
+void dlm_receive_buffer(struct dlm_header *hd, int nodeid)
+{
+ struct dlm_message *ms = (struct dlm_message *) hd;
+ struct dlm_rcom *rc = (struct dlm_rcom *) hd;
+ struct dlm_ls *ls;
+ int type = 0;
+
+ switch (hd->h_cmd) {
+ case DLM_MSG:
+ dlm_message_in(ms);
+ type = ms->m_type;
+ break;
+ case DLM_RCOM:
+ dlm_rcom_in(rc);
+ type = rc->rc_type;
+ break;
+ default:
+ log_print("invalid h_cmd %d from %u", hd->h_cmd, nodeid);
+ return;
+ }
+
+ if (hd->h_nodeid != nodeid) {
+ log_print("invalid h_nodeid %d from %d lockspace %x",
+ hd->h_nodeid, nodeid, hd->h_lockspace);
+ return;
+ }
+
+ ls = dlm_find_lockspace_global(hd->h_lockspace);
+ if (!ls) {
+ log_print("invalid h_lockspace %x from %d cmd %d type %d",
+ hd->h_lockspace, nodeid, hd->h_cmd, type);
+
+ if (hd->h_cmd == DLM_RCOM && type == DLM_RCOM_STATUS)
+ dlm_send_ls_not_ready(nodeid, rc);
+ return;
+ }
+
+ /* this rwsem allows dlm_ls_stop() to wait for all dlm_recv threads to
+ be inactive (in this ls) before transitioning to recovery mode */
+
+ down_read(&ls->ls_recv_active);
+ if (hd->h_cmd == DLM_MSG)
+ dlm_receive_message(ls, ms, nodeid);
+ else
+ dlm_receive_rcom(ls, rc, nodeid);
+ up_read(&ls->ls_recv_active);
+
+ dlm_put_lockspace(ls);
+}

static void recover_convert_waiter(struct dlm_ls *ls, struct dlm_lkb *lkb)
{
diff --git a/fs/dlm/lock.h b/fs/dlm/lock.h
index 1720313..ada0468 100644
--- a/fs/dlm/lock.h
+++ b/fs/dlm/lock.h
@@ -16,7 +16,8 @@
void dlm_print_rsb(struct dlm_rsb *r);
void dlm_dump_rsb(struct dlm_rsb *r);
void dlm_print_lkb(struct dlm_lkb *lkb);
-int dlm_receive_message(struct dlm_header *hd, int nodeid, int recovery);
+void dlm_receive_message_saved(struct dlm_ls *ls, struct dlm_message *ms);
+void dlm_receive_buffer(struct dlm_header *hd, int nodeid);
int dlm_modes_compat(int mode1, int mode2);
int dlm_find_rsb(struct dlm_ls *ls, char *name, int namelen,
unsigned int flags, struct dlm_rsb **r_ret);
diff --git a/fs/dlm/lockspace.c b/fs/dlm/lockspace.c
index 1dc7210..628eaa6 100644
--- a/fs/dlm/lockspace.c
+++ b/fs/dlm/lockspace.c
@@ -519,6 +519,7 @@ static int new_lockspace(char *name, int namelen, void **lockspace,
ls->ls_recover_seq = 0;
ls->ls_recover_args = NULL;
init_rwsem(&ls->ls_in_recovery);
+ init_rwsem(&ls->ls_recv_active);
INIT_LIST_HEAD(&ls->ls_requestqueue);
mutex_init(&ls->ls_requestqueue_mutex);
mutex_init(&ls->ls_clear_proc_locks);
diff --git a/fs/dlm/member.c b/fs/dlm/member.c
index d099775..e9cdcab 100644
--- a/fs/dlm/member.c
+++ b/fs/dlm/member.c
@@ -18,10 +18,6 @@
#include "rcom.h"
#include "config.h"

-/*
- * Following called by dlm_recoverd thread
- */
-
static void add_ordered_member(struct dlm_ls *ls, struct dlm_member *new)
{
struct dlm_member *memb = NULL;
@@ -250,18 +246,30 @@ int dlm_recover_members(struct dlm_ls *ls, struct dlm_recover *rv, int *neg_out)
return error;
}

-/*
- * Following called from lockspace.c
- */
+/* Userspace guarantees that dlm_ls_stop() has completed on all nodes before
+ dlm_ls_start() is called on any of them to start the new recovery. */

int dlm_ls_stop(struct dlm_ls *ls)
{
int new;

/*
- * A stop cancels any recovery that's in progress (see RECOVERY_STOP,
- * dlm_recovery_stopped()) and prevents any new locks from being
- * processed (see RUNNING, dlm_locking_stopped()).
+ * Prevent dlm_recv from being in the middle of something when we do
+ * the stop. This includes ensuring dlm_recv isn't processing a
+ * recovery message (rcom), while dlm_recoverd is aborting and
+ * resetting things from an in-progress recovery. i.e. we want
+ * dlm_recoverd to abort its recovery without worrying about dlm_recv
+ * processing an rcom at the same time. Stopping dlm_recv also makes
+ * it easy for dlm_receive_message() to check locking stopped and add a
+ * message to the requestqueue without races.
+ */
+
+ down_write(&ls->ls_recv_active);
+
+ /*
+ * Abort any recovery that's in progress (see RECOVERY_STOP,
+ * dlm_recovery_stopped()) and tell any other threads running in the
+ * dlm to quit any processing (see RUNNING, dlm_locking_stopped()).
*/

spin_lock(&ls->ls_recover_lock);
@@ -271,8 +279,14 @@ int dlm_ls_stop(struct dlm_ls *ls)
spin_unlock(&ls->ls_recover_lock);

/*
+ * Let dlm_recv run again, now any normal messages will be saved on the
+ * requestqueue for later.
+ */
+
+ up_write(&ls->ls_recv_active);
+
+ /*
* This in_recovery lock does two things:
- *
* 1) Keeps this function from returning until all threads are out
* of locking routines and locking is truely stopped.
* 2) Keeps any new requests from being processed until it's unlocked
@@ -284,9 +298,8 @@ int dlm_ls_stop(struct dlm_ls *ls)

/*
* The recoverd suspend/resume makes sure that dlm_recoverd (if
- * running) has noticed the clearing of RUNNING above and quit
- * processing the previous recovery. This will be true for all nodes
- * before any nodes start the new recovery.
+ * running) has noticed RECOVERY_STOP above and quit processing the
+ * previous recovery.
*/

dlm_recoverd_suspend(ls);
diff --git a/fs/dlm/midcomms.c b/fs/dlm/midcomms.c
index a5126e0..f8c69dd 100644
--- a/fs/dlm/midcomms.c
+++ b/fs/dlm/midcomms.c
@@ -2,7 +2,7 @@
*******************************************************************************
**
** Copyright (C) Sistina Software, Inc. 1997-2003 All rights reserved.
-** Copyright (C) 2004-2005 Red Hat, Inc. All rights reserved.
+** Copyright (C) 2004-2007 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
@@ -27,7 +27,6 @@
#include "dlm_internal.h"
#include "lowcomms.h"
#include "config.h"
-#include "rcom.h"
#include "lock.h"
#include "midcomms.h"

@@ -117,19 +116,7 @@ int dlm_process_incoming_buffer(int nodeid, const void *base,
offset &= (limit - 1);
len -= msglen;

- switch (msg->h_cmd) {
- case DLM_MSG:
- dlm_receive_message(msg, nodeid, 0);
- break;
-
- case DLM_RCOM:
- dlm_receive_rcom(msg, nodeid);
- break;
-
- default:
- log_print("unknown msg type %x from %u: %u %u %u %u",
- msg->h_cmd, nodeid, msglen, len, offset, ret);
- }
+ dlm_receive_buffer(msg, nodeid);
}

if (msg != (struct dlm_header *) __tmp)
diff --git a/fs/dlm/rcom.c b/fs/dlm/rcom.c
index 188b91c..ae2fd97 100644
--- a/fs/dlm/rcom.c
+++ b/fs/dlm/rcom.c
@@ -2,7 +2,7 @@
*******************************************************************************
**
** Copyright (C) Sistina Software, Inc. 1997-2003 All rights reserved.
-** 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
@@ -386,7 +386,10 @@ static void receive_rcom_lock_reply(struct dlm_ls *ls, struct dlm_rcom *rc_in)
dlm_recover_process_copy(ls, rc_in);
}

-static int send_ls_not_ready(int nodeid, struct dlm_rcom *rc_in)
+/* If the lockspace doesn't exist then still send a status message
+ back; it's possible that it just doesn't have its global_id yet. */
+
+int dlm_send_ls_not_ready(int nodeid, struct dlm_rcom *rc_in)
{
struct dlm_rcom *rc;
struct rcom_config *rf;
@@ -446,28 +449,11 @@ static int is_old_reply(struct dlm_ls *ls, struct dlm_rcom *rc)
return rv;
}

-/* Called by dlm_recvd; corresponds to dlm_receive_message() but special
+/* Called by dlm_recv; corresponds to dlm_receive_message() but special
recovery-only comms are sent through here. */

-void dlm_receive_rcom(struct dlm_header *hd, int nodeid)
+void dlm_receive_rcom(struct dlm_ls *ls, struct dlm_rcom *rc, int nodeid)
{
- struct dlm_rcom *rc = (struct dlm_rcom *) hd;
- struct dlm_ls *ls;
-
- dlm_rcom_in(rc);
-
- /* If the lockspace doesn't exist then still send a status message
- back; it's possible that it just doesn't have its global_id yet. */
-
- ls = dlm_find_lockspace_global(hd->h_lockspace);
- if (!ls) {
- log_print("lockspace %x from %d type %x not found",
- hd->h_lockspace, nodeid, rc->rc_type);
- if (rc->rc_type == DLM_RCOM_STATUS)
- send_ls_not_ready(nodeid, rc);
- return;
- }
-
if (dlm_recovery_stopped(ls) && (rc->rc_type != DLM_RCOM_STATUS)) {
log_debug(ls, "ignoring recovery message %x from %d",
rc->rc_type, nodeid);
@@ -477,12 +463,6 @@ void dlm_receive_rcom(struct dlm_header *hd, int nodeid)
if (is_old_reply(ls, rc))
goto out;

- if (nodeid != rc->rc_header.h_nodeid) {
- log_error(ls, "bad rcom nodeid %d from %d",
- rc->rc_header.h_nodeid, nodeid);
- goto out;
- }
-
switch (rc->rc_type) {
case DLM_RCOM_STATUS:
receive_rcom_status(ls, rc);
@@ -520,6 +500,6 @@ void dlm_receive_rcom(struct dlm_header *hd, int nodeid)
DLM_ASSERT(0, printk("rc_type=%x\n", rc->rc_type););
}
out:
- dlm_put_lockspace(ls);
+ return;
}

diff --git a/fs/dlm/rcom.h b/fs/dlm/rcom.h
index d798432..b09abd2 100644
--- a/fs/dlm/rcom.h
+++ b/fs/dlm/rcom.h
@@ -2,7 +2,7 @@
*******************************************************************************
**
** Copyright (C) Sistina Software, Inc. 1997-2003 All rights reserved.
-** 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
@@ -18,7 +18,8 @@ int dlm_rcom_status(struct dlm_ls *ls, int nodeid);
int dlm_rcom_names(struct dlm_ls *ls, int nodeid, char *last_name,int last_len);
int dlm_send_rcom_lookup(struct dlm_rsb *r, int dir_nodeid);
int dlm_send_rcom_lock(struct dlm_rsb *r, struct dlm_lkb *lkb);
-void dlm_receive_rcom(struct dlm_header *hd, int nodeid);
+void dlm_receive_rcom(struct dlm_ls *ls, struct dlm_rcom *rc, int nodeid);
+int dlm_send_ls_not_ready(int nodeid, struct dlm_rcom *rc_in);

#endif

diff --git a/fs/dlm/recoverd.c b/fs/dlm/recoverd.c
index 6657599..4b89e20 100644
--- a/fs/dlm/recoverd.c
+++ b/fs/dlm/recoverd.c
@@ -24,19 +24,28 @@

/* If the start for which we're re-enabling locking (seq) has been superseded
- by a newer stop (ls_recover_seq), we need to leave locking disabled. */
+ by a newer stop (ls_recover_seq), we need to leave locking disabled.
+
+ We suspend dlm_recv threads here to avoid the race where dlm_recv a) sees
+ locking stopped and b) adds a message to the requestqueue, but dlm_recoverd
+ enables locking and clears the requestqueue between a and b. */

static int enable_locking(struct dlm_ls *ls, uint64_t seq)
{
int error = -EINTR;

+ down_write(&ls->ls_recv_active);
+
spin_lock(&ls->ls_recover_lock);
if (ls->ls_recover_seq == seq) {
set_bit(LSFL_RUNNING, &ls->ls_flags);
+ /* unblocks processes waiting to enter the dlm */
up_write(&ls->ls_in_recovery);
error = 0;
}
spin_unlock(&ls->ls_recover_lock);
+
+ up_write(&ls->ls_recv_active);
return error;
}

diff --git a/fs/dlm/requestqueue.c b/fs/dlm/requestqueue.c
index 65008d7..0de04f1 100644
--- a/fs/dlm/requestqueue.c
+++ b/fs/dlm/requestqueue.c
@@ -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();
}
diff --git a/fs/dlm/requestqueue.h b/fs/dlm/requestqueue.h
index 6a53ea0..aba34fc 100644
--- a/fs/dlm/requestqueue.h
+++ b/fs/dlm/requestqueue.h
@@ -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
@@ -13,7 +13,7 @@
#ifndef __REQUESTQUEUE_DOT_H__
#define __REQUESTQUEUE_DOT_H__

-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);
int dlm_process_requestqueue(struct dlm_ls *ls);
void dlm_wait_requestqueue(struct dlm_ls *ls);
void dlm_purge_requestqueue(struct dlm_ls *ls);
--
1.5.1.2