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zfs-builds-mm/zfs-0.8.3/module/zfs/mmp.c

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/*
* 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
*/
/*
* Copyright (c) 2017 by Lawrence Livermore National Security, LLC.
*/
#include <sys/abd.h>
#include <sys/mmp.h>
#include <sys/spa.h>
#include <sys/spa_impl.h>
#include <sys/time.h>
#include <sys/vdev.h>
#include <sys/vdev_impl.h>
#include <sys/zfs_context.h>
#include <sys/callb.h>
/*
* Multi-Modifier Protection (MMP) attempts to prevent a user from importing
* or opening a pool on more than one host at a time. In particular, it
* prevents "zpool import -f" on a host from succeeding while the pool is
* already imported on another host. There are many other ways in which a
* device could be used by two hosts for different purposes at the same time
* resulting in pool damage. This implementation does not attempt to detect
* those cases.
*
* MMP operates by ensuring there are frequent visible changes on disk (a
* "heartbeat") at all times. And by altering the import process to check
* for these changes and failing the import when they are detected. This
* functionality is enabled by setting the 'multihost' pool property to on.
*
* Uberblocks written by the txg_sync thread always go into the first
* (N-MMP_BLOCKS_PER_LABEL) slots, the remaining slots are reserved for MMP.
* They are used to hold uberblocks which are exactly the same as the last
* synced uberblock except that the ub_timestamp and mmp_config are frequently
* updated. Like all other uberblocks, the slot is written with an embedded
* checksum, and slots with invalid checksums are ignored. This provides the
* "heartbeat", with no risk of overwriting good uberblocks that must be
* preserved, e.g. previous txgs and associated block pointers.
*
* Three optional fields are added to uberblock structure; ub_mmp_magic,
* ub_mmp_config, and ub_mmp_delay. The ub_mmp_magic value allows zfs to tell
* whether the other ub_mmp_* fields are valid. The ub_mmp_config field tells
* the importing host the settings of zfs_multihost_interval and
* zfs_multihost_fail_intervals on the host which last had (or currently has)
* the pool imported. These determine how long a host must wait to detect
* activity in the pool, before concluding the pool is not in use. The
* mmp_delay field is a decaying average of the amount of time between
* completion of successive MMP writes, in nanoseconds. It indicates whether
* MMP is enabled.
*
* During import an activity test may now be performed to determine if
* the pool is in use. The activity test is typically required if the
* ZPOOL_CONFIG_HOSTID does not match the system hostid, the pool state is
* POOL_STATE_ACTIVE, and the pool is not a root pool.
*
* The activity test finds the "best" uberblock (highest txg, timestamp, and, if
* ub_mmp_magic is valid, sequence number from ub_mmp_config). It then waits
* some time, and finds the "best" uberblock again. If any of the mentioned
* fields have different values in the newly read uberblock, the pool is in use
* by another host and the import fails. In order to assure the accuracy of the
* activity test, the default values result in an activity test duration of 20x
* the mmp write interval.
*
* The duration of the "zpool import" activity test depends on the information
* available in the "best" uberblock:
*
* 1) If uberblock was written by zfs-0.8 or newer and fail_intervals > 0:
* ub_mmp_config.fail_intervals * ub_mmp_config.multihost_interval * 2
*
* In this case, a weak guarantee is provided. Since the host which last had
* the pool imported will suspend the pool if no mmp writes land within
* fail_intervals * multihost_interval ms, the absence of writes during that
* time means either the pool is not imported, or it is imported but the pool
* is suspended and no further writes will occur.
*
* Note that resuming the suspended pool on the remote host would invalidate
* this guarantee, and so it is not allowed.
*
* The factor of 2 provides a conservative safety factor and derives from
* MMP_IMPORT_SAFETY_FACTOR;
*
* 2) If uberblock was written by zfs-0.8 or newer and fail_intervals == 0:
* (ub_mmp_config.multihost_interval + ub_mmp_delay) *
* zfs_multihost_import_intervals
*
* In this case no guarantee can provided. However, as long as some devices
* are healthy and connected, it is likely that at least one write will land
* within (multihost_interval + mmp_delay) because multihost_interval is
* enough time for a write to be attempted to each leaf vdev, and mmp_delay
* is enough for one to land, based on past delays. Multiplying by
* zfs_multihost_import_intervals provides a conservative safety factor.
*
* 3) If uberblock was written by zfs-0.7:
* (zfs_multihost_interval + ub_mmp_delay) * zfs_multihost_import_intervals
*
* The same logic as case #2 applies, but we do not know remote tunables.
*
* We use the local value for zfs_multihost_interval because the original MMP
* did not record this value in the uberblock.
*
* ub_mmp_delay >= (zfs_multihost_interval / leaves), so if the other host
* has a much larger zfs_multihost_interval set, ub_mmp_delay will reflect
* that. We will have waited enough time for zfs_multihost_import_intervals
* writes to be issued and all but one to land.
*
* single device pool example delays
*
* import_delay = (1 + 1) * 20 = 40s #defaults, no I/O delay
* import_delay = (1 + 10) * 20 = 220s #defaults, 10s I/O delay
* import_delay = (10 + 10) * 20 = 400s #10s multihost_interval,
* no I/O delay
* 100 device pool example delays
*
* import_delay = (1 + .01) * 20 = 20s #defaults, no I/O delay
* import_delay = (1 + 10) * 20 = 220s #defaults, 10s I/O delay
* import_delay = (10 + .1) * 20 = 202s #10s multihost_interval,
* no I/O delay
*
* 4) Otherwise, this uberblock was written by a pre-MMP zfs:
* zfs_multihost_import_intervals * zfs_multihost_interval
*
* In this case local tunables are used. By default this product = 10s, long
* enough for a pool with any activity at all to write at least one
* uberblock. No guarantee can be provided.
*
* Additionally, the duration is then extended by a random 25% to attempt to to
* detect simultaneous imports. For example, if both partner hosts are rebooted
* at the same time and automatically attempt to import the pool.
*/
/*
* Used to control the frequency of mmp writes which are performed when the
* 'multihost' pool property is on. This is one factor used to determine the
* length of the activity check during import.
*
* On average an mmp write will be issued for each leaf vdev every
* zfs_multihost_interval milliseconds. In practice, the observed period can
* vary with the I/O load and this observed value is the ub_mmp_delay which is
* stored in the uberblock. The minimum allowed value is 100 ms.
*/
ulong_t zfs_multihost_interval = MMP_DEFAULT_INTERVAL;
/*
* Used to control the duration of the activity test on import. Smaller values
* of zfs_multihost_import_intervals will reduce the import time but increase
* the risk of failing to detect an active pool. The total activity check time
* is never allowed to drop below one second. A value of 0 is ignored and
* treated as if it was set to 1.
*/
uint_t zfs_multihost_import_intervals = MMP_DEFAULT_IMPORT_INTERVALS;
/*
* Controls the behavior of the pool when mmp write failures or delays are
* detected.
*
* When zfs_multihost_fail_intervals = 0, mmp write failures or delays are
* ignored. The failures will still be reported to the ZED which depending on
* its configuration may take action such as suspending the pool or taking a
* device offline.
*
* When zfs_multihost_fail_intervals > 0, the pool will be suspended if
* zfs_multihost_fail_intervals * zfs_multihost_interval milliseconds pass
* without a successful mmp write. This guarantees the activity test will see
* mmp writes if the pool is imported. A value of 1 is ignored and treated as
* if it was set to 2, because a single leaf vdev pool will issue a write once
* per multihost_interval and thus any variation in latency would cause the
* pool to be suspended.
*/
uint_t zfs_multihost_fail_intervals = MMP_DEFAULT_FAIL_INTERVALS;
char *mmp_tag = "mmp_write_uberblock";
static void mmp_thread(void *arg);
void
mmp_init(spa_t *spa)
{
mmp_thread_t *mmp = &spa->spa_mmp;
mutex_init(&mmp->mmp_thread_lock, NULL, MUTEX_DEFAULT, NULL);
cv_init(&mmp->mmp_thread_cv, NULL, CV_DEFAULT, NULL);
mutex_init(&mmp->mmp_io_lock, NULL, MUTEX_DEFAULT, NULL);
mmp->mmp_kstat_id = 1;
/*
* mmp_write_done() calculates mmp_delay based on prior mmp_delay and
* the elapsed time since the last write. For the first mmp write,
* there is no "last write", so we start with fake non-zero values.
*/
mmp->mmp_last_write = gethrtime();
mmp->mmp_delay = MSEC2NSEC(MMP_INTERVAL_OK(zfs_multihost_interval));
}
void
mmp_fini(spa_t *spa)
{
mmp_thread_t *mmp = &spa->spa_mmp;
mutex_destroy(&mmp->mmp_thread_lock);
cv_destroy(&mmp->mmp_thread_cv);
mutex_destroy(&mmp->mmp_io_lock);
}
static void
mmp_thread_enter(mmp_thread_t *mmp, callb_cpr_t *cpr)
{
CALLB_CPR_INIT(cpr, &mmp->mmp_thread_lock, callb_generic_cpr, FTAG);
mutex_enter(&mmp->mmp_thread_lock);
}
static void
mmp_thread_exit(mmp_thread_t *mmp, kthread_t **mpp, callb_cpr_t *cpr)
{
ASSERT(*mpp != NULL);
*mpp = NULL;
cv_broadcast(&mmp->mmp_thread_cv);
CALLB_CPR_EXIT(cpr); /* drops &mmp->mmp_thread_lock */
thread_exit();
}
void
mmp_thread_start(spa_t *spa)
{
mmp_thread_t *mmp = &spa->spa_mmp;
if (spa_writeable(spa)) {
mutex_enter(&mmp->mmp_thread_lock);
if (!mmp->mmp_thread) {
mmp->mmp_thread = thread_create(NULL, 0, mmp_thread,
spa, 0, &p0, TS_RUN, defclsyspri);
zfs_dbgmsg("MMP thread started pool '%s' "
"gethrtime %llu", spa_name(spa), gethrtime());
}
mutex_exit(&mmp->mmp_thread_lock);
}
}
void
mmp_thread_stop(spa_t *spa)
{
mmp_thread_t *mmp = &spa->spa_mmp;
mutex_enter(&mmp->mmp_thread_lock);
mmp->mmp_thread_exiting = 1;
cv_broadcast(&mmp->mmp_thread_cv);
while (mmp->mmp_thread) {
cv_wait(&mmp->mmp_thread_cv, &mmp->mmp_thread_lock);
}
mutex_exit(&mmp->mmp_thread_lock);
zfs_dbgmsg("MMP thread stopped pool '%s' gethrtime %llu",
spa_name(spa), gethrtime());
ASSERT(mmp->mmp_thread == NULL);
mmp->mmp_thread_exiting = 0;
}
typedef enum mmp_vdev_state_flag {
MMP_FAIL_NOT_WRITABLE = (1 << 0),
MMP_FAIL_WRITE_PENDING = (1 << 1),
} mmp_vdev_state_flag_t;
/*
* Find a leaf vdev to write an MMP block to. It must not have an outstanding
* mmp write (if so a new write will also likely block). If there is no usable
* leaf, a nonzero error value is returned. The error value returned is a bit
* field.
*
* MMP_FAIL_WRITE_PENDING One or more leaf vdevs are writeable, but have an
* outstanding MMP write.
* MMP_FAIL_NOT_WRITABLE One or more leaf vdevs are not writeable.
*/
static int
mmp_next_leaf(spa_t *spa)
{
vdev_t *leaf;
vdev_t *starting_leaf;
int fail_mask = 0;
ASSERT(MUTEX_HELD(&spa->spa_mmp.mmp_io_lock));
ASSERT(spa_config_held(spa, SCL_STATE, RW_READER));
ASSERT(list_link_active(&spa->spa_leaf_list.list_head) == B_TRUE);
ASSERT(!list_is_empty(&spa->spa_leaf_list));
if (spa->spa_mmp.mmp_leaf_last_gen != spa->spa_leaf_list_gen) {
spa->spa_mmp.mmp_last_leaf = list_head(&spa->spa_leaf_list);
spa->spa_mmp.mmp_leaf_last_gen = spa->spa_leaf_list_gen;
}
leaf = spa->spa_mmp.mmp_last_leaf;
if (leaf == NULL)
leaf = list_head(&spa->spa_leaf_list);
starting_leaf = leaf;
do {
leaf = list_next(&spa->spa_leaf_list, leaf);
if (leaf == NULL)
leaf = list_head(&spa->spa_leaf_list);
if (!vdev_writeable(leaf)) {
fail_mask |= MMP_FAIL_NOT_WRITABLE;
} else if (leaf->vdev_mmp_pending != 0) {
fail_mask |= MMP_FAIL_WRITE_PENDING;
} else {
spa->spa_mmp.mmp_last_leaf = leaf;
return (0);
}
} while (leaf != starting_leaf);
ASSERT(fail_mask);
return (fail_mask);
}
/*
* MMP writes are issued on a fixed schedule, but may complete at variable,
* much longer, intervals. The mmp_delay captures long periods between
* successful writes for any reason, including disk latency, scheduling delays,
* etc.
*
* The mmp_delay is usually calculated as a decaying average, but if the latest
* delay is higher we do not average it, so that we do not hide sudden spikes
* which the importing host must wait for.
*
* If writes are occurring frequently, such as due to a high rate of txg syncs,
* the mmp_delay could become very small. Since those short delays depend on
* activity we cannot count on, we never allow mmp_delay to get lower than rate
* expected if only mmp_thread writes occur.
*
* If an mmp write was skipped or fails, and we have already waited longer than
* mmp_delay, we need to update it so the next write reflects the longer delay.
*
* Do not set mmp_delay if the multihost property is not on, so as not to
* trigger an activity check on import.
*/
static void
mmp_delay_update(spa_t *spa, boolean_t write_completed)
{
mmp_thread_t *mts = &spa->spa_mmp;
hrtime_t delay = gethrtime() - mts->mmp_last_write;
ASSERT(MUTEX_HELD(&mts->mmp_io_lock));
if (spa_multihost(spa) == B_FALSE) {
mts->mmp_delay = 0;
return;
}
if (delay > mts->mmp_delay)
mts->mmp_delay = delay;
if (write_completed == B_FALSE)
return;
mts->mmp_last_write = gethrtime();
/*
* strictly less than, in case delay was changed above.
*/
if (delay < mts->mmp_delay) {
hrtime_t min_delay =
MSEC2NSEC(MMP_INTERVAL_OK(zfs_multihost_interval)) /
MAX(1, vdev_count_leaves(spa));
mts->mmp_delay = MAX(((delay + mts->mmp_delay * 127) / 128),
min_delay);
}
}
static void
mmp_write_done(zio_t *zio)
{
spa_t *spa = zio->io_spa;
vdev_t *vd = zio->io_vd;
mmp_thread_t *mts = zio->io_private;
mutex_enter(&mts->mmp_io_lock);
uint64_t mmp_kstat_id = vd->vdev_mmp_kstat_id;
hrtime_t mmp_write_duration = gethrtime() - vd->vdev_mmp_pending;
mmp_delay_update(spa, (zio->io_error == 0));
vd->vdev_mmp_pending = 0;
vd->vdev_mmp_kstat_id = 0;
mutex_exit(&mts->mmp_io_lock);
spa_config_exit(spa, SCL_STATE, mmp_tag);
spa_mmp_history_set(spa, mmp_kstat_id, zio->io_error,
mmp_write_duration);
abd_free(zio->io_abd);
}
/*
* When the uberblock on-disk is updated by a spa_sync,
* creating a new "best" uberblock, update the one stored
* in the mmp thread state, used for mmp writes.
*/
void
mmp_update_uberblock(spa_t *spa, uberblock_t *ub)
{
mmp_thread_t *mmp = &spa->spa_mmp;
mutex_enter(&mmp->mmp_io_lock);
mmp->mmp_ub = *ub;
mmp->mmp_seq = 1;
mmp->mmp_ub.ub_timestamp = gethrestime_sec();
mmp_delay_update(spa, B_TRUE);
mutex_exit(&mmp->mmp_io_lock);
}
/*
* Choose a random vdev, label, and MMP block, and write over it
* with a copy of the last-synced uberblock, whose timestamp
* has been updated to reflect that the pool is in use.
*/
static void
mmp_write_uberblock(spa_t *spa)
{
int flags = ZIO_FLAG_CONFIG_WRITER | ZIO_FLAG_CANFAIL;
mmp_thread_t *mmp = &spa->spa_mmp;
uberblock_t *ub;
vdev_t *vd = NULL;
int label, error;
uint64_t offset;
hrtime_t lock_acquire_time = gethrtime();
spa_config_enter(spa, SCL_STATE, mmp_tag, RW_READER);
lock_acquire_time = gethrtime() - lock_acquire_time;
if (lock_acquire_time > (MSEC2NSEC(MMP_MIN_INTERVAL) / 10))
zfs_dbgmsg("MMP SCL_STATE acquisition pool '%s' took %llu ns "
"gethrtime %llu", spa_name(spa), lock_acquire_time,
gethrtime());
mutex_enter(&mmp->mmp_io_lock);
error = mmp_next_leaf(spa);
/*
* spa_mmp_history has two types of entries:
* Issued MMP write: records time issued, error status, etc.
* Skipped MMP write: an MMP write could not be issued because no
* suitable leaf vdev was available. See comment above struct
* spa_mmp_history for details.
*/
if (error) {
mmp_delay_update(spa, B_FALSE);
if (mmp->mmp_skip_error == error) {
spa_mmp_history_set_skip(spa, mmp->mmp_kstat_id - 1);
} else {
mmp->mmp_skip_error = error;
spa_mmp_history_add(spa, mmp->mmp_ub.ub_txg,
gethrestime_sec(), mmp->mmp_delay, NULL, 0,
mmp->mmp_kstat_id++, error);
zfs_dbgmsg("MMP error choosing leaf pool '%s' "
"gethrtime %llu fail_mask %#x", spa_name(spa),
gethrtime(), error);
}
mutex_exit(&mmp->mmp_io_lock);
spa_config_exit(spa, SCL_STATE, mmp_tag);
return;
}
vd = spa->spa_mmp.mmp_last_leaf;
if (mmp->mmp_skip_error != 0) {
mmp->mmp_skip_error = 0;
zfs_dbgmsg("MMP write after skipping due to unavailable "
"leaves, pool '%s' gethrtime %llu leaf %#llu",
spa_name(spa), gethrtime(), vd->vdev_guid);
}
if (mmp->mmp_zio_root == NULL)
mmp->mmp_zio_root = zio_root(spa, NULL, NULL,
flags | ZIO_FLAG_GODFATHER);
if (mmp->mmp_ub.ub_timestamp != gethrestime_sec()) {
/*
* Want to reset mmp_seq when timestamp advances because after
* an mmp_seq wrap new values will not be chosen by
* uberblock_compare() as the "best".
*/
mmp->mmp_ub.ub_timestamp = gethrestime_sec();
mmp->mmp_seq = 1;
}
ub = &mmp->mmp_ub;
ub->ub_mmp_magic = MMP_MAGIC;
ub->ub_mmp_delay = mmp->mmp_delay;
ub->ub_mmp_config = MMP_SEQ_SET(mmp->mmp_seq) |
MMP_INTERVAL_SET(MMP_INTERVAL_OK(zfs_multihost_interval)) |
MMP_FAIL_INT_SET(MMP_FAIL_INTVS_OK(
zfs_multihost_fail_intervals));
vd->vdev_mmp_pending = gethrtime();
vd->vdev_mmp_kstat_id = mmp->mmp_kstat_id;
zio_t *zio = zio_null(mmp->mmp_zio_root, spa, NULL, NULL, NULL, flags);
abd_t *ub_abd = abd_alloc_for_io(VDEV_UBERBLOCK_SIZE(vd), B_TRUE);
abd_zero(ub_abd, VDEV_UBERBLOCK_SIZE(vd));
abd_copy_from_buf(ub_abd, ub, sizeof (uberblock_t));
mmp->mmp_seq++;
mmp->mmp_kstat_id++;
mutex_exit(&mmp->mmp_io_lock);
offset = VDEV_UBERBLOCK_OFFSET(vd, VDEV_UBERBLOCK_COUNT(vd) -
MMP_BLOCKS_PER_LABEL + spa_get_random(MMP_BLOCKS_PER_LABEL));
label = spa_get_random(VDEV_LABELS);
vdev_label_write(zio, vd, label, ub_abd, offset,
VDEV_UBERBLOCK_SIZE(vd), mmp_write_done, mmp,
flags | ZIO_FLAG_DONT_PROPAGATE);
(void) spa_mmp_history_add(spa, ub->ub_txg, ub->ub_timestamp,
ub->ub_mmp_delay, vd, label, vd->vdev_mmp_kstat_id, 0);
zio_nowait(zio);
}
static void
mmp_thread(void *arg)
{
spa_t *spa = (spa_t *)arg;
mmp_thread_t *mmp = &spa->spa_mmp;
boolean_t suspended = spa_suspended(spa);
boolean_t multihost = spa_multihost(spa);
uint64_t mmp_interval = MSEC2NSEC(MMP_INTERVAL_OK(
zfs_multihost_interval));
uint32_t mmp_fail_intervals = MMP_FAIL_INTVS_OK(
zfs_multihost_fail_intervals);
hrtime_t mmp_fail_ns = mmp_fail_intervals * mmp_interval;
boolean_t last_spa_suspended = suspended;
boolean_t last_spa_multihost = multihost;
uint64_t last_mmp_interval = mmp_interval;
uint32_t last_mmp_fail_intervals = mmp_fail_intervals;
hrtime_t last_mmp_fail_ns = mmp_fail_ns;
callb_cpr_t cpr;
int skip_wait = 0;
mmp_thread_enter(mmp, &cpr);
while (!mmp->mmp_thread_exiting) {
hrtime_t next_time = gethrtime() +
MSEC2NSEC(MMP_DEFAULT_INTERVAL);
int leaves = MAX(vdev_count_leaves(spa), 1);
/* Detect changes in tunables or state */
last_spa_suspended = suspended;
last_spa_multihost = multihost;
suspended = spa_suspended(spa);
multihost = spa_multihost(spa);
last_mmp_interval = mmp_interval;
last_mmp_fail_intervals = mmp_fail_intervals;
last_mmp_fail_ns = mmp_fail_ns;
mmp_interval = MSEC2NSEC(MMP_INTERVAL_OK(
zfs_multihost_interval));
mmp_fail_intervals = MMP_FAIL_INTVS_OK(
zfs_multihost_fail_intervals);
/* Smooth so pool is not suspended when reducing tunables */
if (mmp_fail_intervals * mmp_interval < mmp_fail_ns) {
mmp_fail_ns = (mmp_fail_ns * 31 +
mmp_fail_intervals * mmp_interval) / 32;
} else {
mmp_fail_ns = mmp_fail_intervals *
mmp_interval;
}
if (mmp_interval != last_mmp_interval ||
mmp_fail_intervals != last_mmp_fail_intervals) {
/*
* We want other hosts to see new tunables as quickly as
* possible. Write out at higher frequency than usual.
*/
skip_wait += leaves;
}
if (multihost)
next_time = gethrtime() + mmp_interval / leaves;
if (mmp_fail_ns != last_mmp_fail_ns) {
zfs_dbgmsg("MMP interval change pool '%s' "
"gethrtime %llu last_mmp_interval %llu "
"mmp_interval %llu last_mmp_fail_intervals %u "
"mmp_fail_intervals %u mmp_fail_ns %llu "
"skip_wait %d leaves %d next_time %llu",
spa_name(spa), gethrtime(), last_mmp_interval,
mmp_interval, last_mmp_fail_intervals,
mmp_fail_intervals, mmp_fail_ns, skip_wait, leaves,
next_time);
}
/*
* MMP off => on, or suspended => !suspended:
* No writes occurred recently. Update mmp_last_write to give
* us some time to try.
*/
if ((!last_spa_multihost && multihost) ||
(last_spa_suspended && !suspended)) {
zfs_dbgmsg("MMP state change pool '%s': gethrtime %llu "
"last_spa_multihost %u multihost %u "
"last_spa_suspended %u suspended %u",
spa_name(spa), last_spa_multihost, multihost,
last_spa_suspended, suspended);
mutex_enter(&mmp->mmp_io_lock);
mmp->mmp_last_write = gethrtime();
mmp->mmp_delay = mmp_interval;
mutex_exit(&mmp->mmp_io_lock);
}
/*
* MMP on => off:
* mmp_delay == 0 tells importing node to skip activity check.
*/
if (last_spa_multihost && !multihost) {
mutex_enter(&mmp->mmp_io_lock);
mmp->mmp_delay = 0;
mutex_exit(&mmp->mmp_io_lock);
}
/*
* Suspend the pool if no MMP write has succeeded in over
* mmp_interval * mmp_fail_intervals nanoseconds.
*/
if (multihost && !suspended && mmp_fail_intervals &&
(gethrtime() - mmp->mmp_last_write) > mmp_fail_ns) {
zfs_dbgmsg("MMP suspending pool '%s': gethrtime %llu "
"mmp_last_write %llu mmp_interval %llu "
"mmp_fail_intervals %llu mmp_fail_ns %llu",
spa_name(spa), (u_longlong_t)gethrtime(),
(u_longlong_t)mmp->mmp_last_write,
(u_longlong_t)mmp_interval,
(u_longlong_t)mmp_fail_intervals,
(u_longlong_t)mmp_fail_ns);
cmn_err(CE_WARN, "MMP writes to pool '%s' have not "
"succeeded in over %llu ms; suspending pool. "
"Hrtime %llu",
spa_name(spa),
NSEC2MSEC(gethrtime() - mmp->mmp_last_write),
gethrtime());
zio_suspend(spa, NULL, ZIO_SUSPEND_MMP);
}
if (multihost && !suspended)
mmp_write_uberblock(spa);
if (skip_wait > 0) {
next_time = gethrtime() + MSEC2NSEC(MMP_MIN_INTERVAL) /
leaves;
skip_wait--;
}
CALLB_CPR_SAFE_BEGIN(&cpr);
(void) cv_timedwait_sig_hires(&mmp->mmp_thread_cv,
&mmp->mmp_thread_lock, next_time, USEC2NSEC(100),
CALLOUT_FLAG_ABSOLUTE);
CALLB_CPR_SAFE_END(&cpr, &mmp->mmp_thread_lock);
}
/* Outstanding writes are allowed to complete. */
if (mmp->mmp_zio_root)
zio_wait(mmp->mmp_zio_root);
mmp->mmp_zio_root = NULL;
mmp_thread_exit(mmp, &mmp->mmp_thread, &cpr);
}
/*
* Signal the MMP thread to wake it, when it is sleeping on
* its cv. Used when some module parameter has changed and
* we want the thread to know about it.
* Only signal if the pool is active and mmp thread is
* running, otherwise there is no thread to wake.
*/
static void
mmp_signal_thread(spa_t *spa)
{
mmp_thread_t *mmp = &spa->spa_mmp;
mutex_enter(&mmp->mmp_thread_lock);
if (mmp->mmp_thread)
cv_broadcast(&mmp->mmp_thread_cv);
mutex_exit(&mmp->mmp_thread_lock);
}
void
mmp_signal_all_threads(void)
{
spa_t *spa = NULL;
mutex_enter(&spa_namespace_lock);
while ((spa = spa_next(spa))) {
if (spa->spa_state == POOL_STATE_ACTIVE)
mmp_signal_thread(spa);
}
mutex_exit(&spa_namespace_lock);
}
#if defined(_KERNEL)
#include <linux/mod_compat.h>
static int
param_set_multihost_interval(const char *val, zfs_kernel_param_t *kp)
{
int ret;
ret = param_set_ulong(val, kp);
if (ret < 0)
return (ret);
if (spa_mode_global != 0)
mmp_signal_all_threads();
return (ret);
}
/* BEGIN CSTYLED */
module_param(zfs_multihost_fail_intervals, uint, 0644);
MODULE_PARM_DESC(zfs_multihost_fail_intervals,
"Max allowed period without a successful mmp write");
module_param_call(zfs_multihost_interval, param_set_multihost_interval,
param_get_ulong, &zfs_multihost_interval, 0644);
MODULE_PARM_DESC(zfs_multihost_interval,
"Milliseconds between mmp writes to each leaf");
module_param(zfs_multihost_import_intervals, uint, 0644);
MODULE_PARM_DESC(zfs_multihost_import_intervals,
"Number of zfs_multihost_interval periods to wait for activity");
/* END CSTYLED */
#endif
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