freebsd-nq/module/zfs/rrwlock.c

278 lines
7.7 KiB
C
Raw Normal View History

2008-11-20 20:01:55 +00:00
/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License (the "License").
* You may not use this file except in compliance with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or http://www.opensolaris.org/os/licensing.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
2009-08-18 18:43:27 +00:00
* Copyright 2009 Sun Microsystems, Inc. All rights reserved.
2008-11-20 20:01:55 +00:00
* Use is subject to license terms.
*/
Illumos #2882, #2883, #2900 2882 implement libzfs_core 2883 changing "canmount" property to "on" should not always remount dataset 2900 "zfs snapshot" should be able to create multiple, arbitrary snapshots at once Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Chris Siden <christopher.siden@delphix.com> Reviewed by: Garrett D'Amore <garrett@damore.org> Reviewed by: Bill Pijewski <wdp@joyent.com> Reviewed by: Dan Kruchinin <dan.kruchinin@gmail.com> Approved by: Eric Schrock <Eric.Schrock@delphix.com> References: https://www.illumos.org/issues/2882 https://www.illumos.org/issues/2883 https://www.illumos.org/issues/2900 illumos/illumos-gate@4445fffbbb1ea25fd0e9ea68b9380dd7a6709025 Ported-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1293 Porting notes: WARNING: This patch changes the user/kernel ABI. That means that the zfs/zpool utilities built from master are NOT compatible with the 0.6.2 kernel modules. Ensure you load the matching kernel modules from master after updating the utilities. Otherwise the zfs/zpool commands will be unable to interact with your pool and you will see errors similar to the following: $ zpool list failed to read pool configuration: bad address no pools available $ zfs list no datasets available Add zvol minor device creation to the new zfs_snapshot_nvl function. Remove the logging of the "release" operation in dsl_dataset_user_release_sync(). The logging caused a null dereference because ds->ds_dir is zeroed in dsl_dataset_destroy_sync() and the logging functions try to get the ds name via the dsl_dataset_name() function. I've got no idea why this particular code would have worked in Illumos. This code has subsequently been completely reworked in Illumos commit 3b2aab1 (3464 zfs synctask code needs restructuring). Squash some "may be used uninitialized" warning/erorrs. Fix some printf format warnings for %lld and %llu. Apply a few spa_writeable() changes that were made to Illumos in illumos/illumos-gate.git@cd1c8b8 as part of the 3112, 3113, 3114 and 3115 fixes. Add a missing call to fnvlist_free(nvl) in log_internal() that was added in Illumos to fix issue 3085 but couldn't be ported to ZoL at the time (zfsonlinux/zfs@9e11c73) because it depended on future work.
2013-08-28 11:45:09 +00:00
/*
* Copyright (c) 2012 by Delphix. All rights reserved.
*/
2008-11-20 20:01:55 +00:00
#include <sys/refcount.h>
#include <sys/rrwlock.h>
/*
* This file contains the implementation of a re-entrant read
* reader/writer lock (aka "rrwlock").
*
* This is a normal reader/writer lock with the additional feature
* of allowing threads who have already obtained a read lock to
* re-enter another read lock (re-entrant read) - even if there are
* waiting writers.
*
* Callers who have not obtained a read lock give waiting writers priority.
*
* The rrwlock_t lock does not allow re-entrant writers, nor does it
* allow a re-entrant mix of reads and writes (that is, it does not
* allow a caller who has already obtained a read lock to be able to
* then grab a write lock without first dropping all read locks, and
* vice versa).
*
* The rrwlock_t uses tsd (thread specific data) to keep a list of
* nodes (rrw_node_t), where each node keeps track of which specific
* lock (rrw_node_t::rn_rrl) the thread has grabbed. Since re-entering
* should be rare, a thread that grabs multiple reads on the same rrwlock_t
* will store multiple rrw_node_ts of the same 'rrn_rrl'. Nodes on the
* tsd list can represent a different rrwlock_t. This allows a thread
* to enter multiple and unique rrwlock_ts for read locks at the same time.
*
* Since using tsd exposes some overhead, the rrwlock_t only needs to
* keep tsd data when writers are waiting. If no writers are waiting, then
* a reader just bumps the anonymous read count (rr_anon_rcount) - no tsd
* is needed. Once a writer attempts to grab the lock, readers then
* keep tsd data and bump the linked readers count (rr_linked_rcount).
*
* If there are waiting writers and there are anonymous readers, then a
* reader doesn't know if it is a re-entrant lock. But since it may be one,
* we allow the read to proceed (otherwise it could deadlock). Since once
* waiting writers are active, readers no longer bump the anonymous count,
* the anonymous readers will eventually flush themselves out. At this point,
* readers will be able to tell if they are a re-entrant lock (have a
* rrw_node_t entry for the lock) or not. If they are a re-entrant lock, then
* we must let the proceed. If they are not, then the reader blocks for the
* waiting writers. Hence, we do not starve writers.
*/
/* global key for TSD */
uint_t rrw_tsd_key;
typedef struct rrw_node {
struct rrw_node *rn_next;
rrwlock_t *rn_rrl;
} rrw_node_t;
static rrw_node_t *
rrn_find(rrwlock_t *rrl)
{
rrw_node_t *rn;
if (refcount_count(&rrl->rr_linked_rcount) == 0)
return (NULL);
for (rn = tsd_get(rrw_tsd_key); rn != NULL; rn = rn->rn_next) {
if (rn->rn_rrl == rrl)
return (rn);
}
return (NULL);
}
/*
* Add a node to the head of the singly linked list.
*/
static void
rrn_add(rrwlock_t *rrl)
{
rrw_node_t *rn;
rn = kmem_alloc(sizeof (*rn), KM_SLEEP);
rn->rn_rrl = rrl;
rn->rn_next = tsd_get(rrw_tsd_key);
VERIFY(tsd_set(rrw_tsd_key, rn) == 0);
}
/*
* If a node is found for 'rrl', then remove the node from this
* thread's list and return TRUE; otherwise return FALSE.
*/
static boolean_t
rrn_find_and_remove(rrwlock_t *rrl)
{
rrw_node_t *rn;
rrw_node_t *prev = NULL;
if (refcount_count(&rrl->rr_linked_rcount) == 0)
2009-08-18 18:43:27 +00:00
return (B_FALSE);
2008-11-20 20:01:55 +00:00
for (rn = tsd_get(rrw_tsd_key); rn != NULL; rn = rn->rn_next) {
if (rn->rn_rrl == rrl) {
if (prev)
prev->rn_next = rn->rn_next;
else
VERIFY(tsd_set(rrw_tsd_key, rn->rn_next) == 0);
kmem_free(rn, sizeof (*rn));
return (B_TRUE);
}
prev = rn;
}
return (B_FALSE);
}
void
rrw_init(rrwlock_t *rrl)
{
mutex_init(&rrl->rr_lock, NULL, MUTEX_DEFAULT, NULL);
cv_init(&rrl->rr_cv, NULL, CV_DEFAULT, NULL);
rrl->rr_writer = NULL;
refcount_create(&rrl->rr_anon_rcount);
refcount_create(&rrl->rr_linked_rcount);
rrl->rr_writer_wanted = B_FALSE;
}
void
rrw_destroy(rrwlock_t *rrl)
{
mutex_destroy(&rrl->rr_lock);
cv_destroy(&rrl->rr_cv);
ASSERT(rrl->rr_writer == NULL);
refcount_destroy(&rrl->rr_anon_rcount);
refcount_destroy(&rrl->rr_linked_rcount);
}
static void
rrw_enter_read(rrwlock_t *rrl, void *tag)
{
mutex_enter(&rrl->rr_lock);
2009-08-18 18:43:27 +00:00
#if !defined(DEBUG) && defined(_KERNEL)
if (!rrl->rr_writer && !rrl->rr_writer_wanted) {
rrl->rr_anon_rcount.rc_count++;
mutex_exit(&rrl->rr_lock);
return;
}
DTRACE_PROBE(zfs__rrwfastpath__rdmiss);
#endif
2008-11-20 20:01:55 +00:00
ASSERT(rrl->rr_writer != curthread);
ASSERT(refcount_count(&rrl->rr_anon_rcount) >= 0);
while (rrl->rr_writer || (rrl->rr_writer_wanted &&
refcount_is_zero(&rrl->rr_anon_rcount) &&
rrn_find(rrl) == NULL))
cv_wait(&rrl->rr_cv, &rrl->rr_lock);
if (rrl->rr_writer_wanted) {
/* may or may not be a re-entrant enter */
rrn_add(rrl);
(void) refcount_add(&rrl->rr_linked_rcount, tag);
} else {
(void) refcount_add(&rrl->rr_anon_rcount, tag);
}
ASSERT(rrl->rr_writer == NULL);
mutex_exit(&rrl->rr_lock);
}
static void
rrw_enter_write(rrwlock_t *rrl)
{
mutex_enter(&rrl->rr_lock);
ASSERT(rrl->rr_writer != curthread);
while (refcount_count(&rrl->rr_anon_rcount) > 0 ||
refcount_count(&rrl->rr_linked_rcount) > 0 ||
rrl->rr_writer != NULL) {
rrl->rr_writer_wanted = B_TRUE;
cv_wait(&rrl->rr_cv, &rrl->rr_lock);
}
rrl->rr_writer_wanted = B_FALSE;
rrl->rr_writer = curthread;
mutex_exit(&rrl->rr_lock);
}
void
rrw_enter(rrwlock_t *rrl, krw_t rw, void *tag)
{
if (rw == RW_READER)
rrw_enter_read(rrl, tag);
else
rrw_enter_write(rrl);
}
void
rrw_exit(rrwlock_t *rrl, void *tag)
{
mutex_enter(&rrl->rr_lock);
2009-08-18 18:43:27 +00:00
#if !defined(DEBUG) && defined(_KERNEL)
if (!rrl->rr_writer && rrl->rr_linked_rcount.rc_count == 0) {
rrl->rr_anon_rcount.rc_count--;
if (rrl->rr_anon_rcount.rc_count == 0)
cv_broadcast(&rrl->rr_cv);
mutex_exit(&rrl->rr_lock);
return;
}
DTRACE_PROBE(zfs__rrwfastpath__exitmiss);
#endif
2008-11-20 20:01:55 +00:00
ASSERT(!refcount_is_zero(&rrl->rr_anon_rcount) ||
!refcount_is_zero(&rrl->rr_linked_rcount) ||
rrl->rr_writer != NULL);
if (rrl->rr_writer == NULL) {
2009-08-18 18:43:27 +00:00
int64_t count;
if (rrn_find_and_remove(rrl))
count = refcount_remove(&rrl->rr_linked_rcount, tag);
else
count = refcount_remove(&rrl->rr_anon_rcount, tag);
if (count == 0)
cv_broadcast(&rrl->rr_cv);
2008-11-20 20:01:55 +00:00
} else {
ASSERT(rrl->rr_writer == curthread);
ASSERT(refcount_is_zero(&rrl->rr_anon_rcount) &&
refcount_is_zero(&rrl->rr_linked_rcount));
rrl->rr_writer = NULL;
cv_broadcast(&rrl->rr_cv);
}
mutex_exit(&rrl->rr_lock);
}
boolean_t
rrw_held(rrwlock_t *rrl, krw_t rw)
{
boolean_t held;
mutex_enter(&rrl->rr_lock);
if (rw == RW_WRITER) {
held = (rrl->rr_writer == curthread);
} else {
held = (!refcount_is_zero(&rrl->rr_anon_rcount) ||
!refcount_is_zero(&rrl->rr_linked_rcount));
}
mutex_exit(&rrl->rr_lock);
return (held);
}
Illumos #2882, #2883, #2900 2882 implement libzfs_core 2883 changing "canmount" property to "on" should not always remount dataset 2900 "zfs snapshot" should be able to create multiple, arbitrary snapshots at once Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Chris Siden <christopher.siden@delphix.com> Reviewed by: Garrett D'Amore <garrett@damore.org> Reviewed by: Bill Pijewski <wdp@joyent.com> Reviewed by: Dan Kruchinin <dan.kruchinin@gmail.com> Approved by: Eric Schrock <Eric.Schrock@delphix.com> References: https://www.illumos.org/issues/2882 https://www.illumos.org/issues/2883 https://www.illumos.org/issues/2900 illumos/illumos-gate@4445fffbbb1ea25fd0e9ea68b9380dd7a6709025 Ported-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1293 Porting notes: WARNING: This patch changes the user/kernel ABI. That means that the zfs/zpool utilities built from master are NOT compatible with the 0.6.2 kernel modules. Ensure you load the matching kernel modules from master after updating the utilities. Otherwise the zfs/zpool commands will be unable to interact with your pool and you will see errors similar to the following: $ zpool list failed to read pool configuration: bad address no pools available $ zfs list no datasets available Add zvol minor device creation to the new zfs_snapshot_nvl function. Remove the logging of the "release" operation in dsl_dataset_user_release_sync(). The logging caused a null dereference because ds->ds_dir is zeroed in dsl_dataset_destroy_sync() and the logging functions try to get the ds name via the dsl_dataset_name() function. I've got no idea why this particular code would have worked in Illumos. This code has subsequently been completely reworked in Illumos commit 3b2aab1 (3464 zfs synctask code needs restructuring). Squash some "may be used uninitialized" warning/erorrs. Fix some printf format warnings for %lld and %llu. Apply a few spa_writeable() changes that were made to Illumos in illumos/illumos-gate.git@cd1c8b8 as part of the 3112, 3113, 3114 and 3115 fixes. Add a missing call to fnvlist_free(nvl) in log_internal() that was added in Illumos to fix issue 3085 but couldn't be ported to ZoL at the time (zfsonlinux/zfs@9e11c73) because it depended on future work.
2013-08-28 11:45:09 +00:00
void
rrw_tsd_destroy(void *arg)
{
rrw_node_t *rn = arg;
if (rn != NULL) {
panic("thread %p terminating with rrw lock %p held",
(void *)curthread, (void *)rn->rn_rrl);
}
}