diff options
Diffstat (limited to 'usr/src/uts/common/fs/zfs/mmp.c')
| -rw-r--r-- | usr/src/uts/common/fs/zfs/mmp.c | 582 |
1 files changed, 582 insertions, 0 deletions
diff --git a/usr/src/uts/common/fs/zfs/mmp.c b/usr/src/uts/common/fs/zfs/mmp.c new file mode 100644 index 0000000000..105e2bfdfd --- /dev/null +++ b/usr/src/uts/common/fs/zfs/mmp.c @@ -0,0 +1,582 @@ +/* + * 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. + * Copyright 2019 Joyent, Inc. + */ + +#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 is 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. + * + * Two optional fields are added to uberblock structure: ub_mmp_magic and + * ub_mmp_delay. The magic field allows zfs to tell whether ub_mmp_delay is + * valid. The delay field is a decaying average of the amount of time between + * completion of successive MMP writes, in nanoseconds. It is used to predict + * how long the import must wait to detect activity in the pool, before + * concluding it is not in use. + * + * 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), + * waits some time, and then finds the "best" uberblock again. If the txg + * and timestamp in both "best" uberblocks do not match, the pool is in use + * by another host and the import fails. Since the granularity of the + * timestamp is in seconds this activity test must take a bare minimum of one + * second. In order to assure the accuracy of the activity test, the default + * values result in an activity test duration of 10x the mmp write interval. + * + * The "zpool import" activity test can be expected to take a minimum time of + * zfs_multihost_import_intervals * zfs_multihost_interval milliseconds. If the + * "best" uberblock has a valid ub_mmp_delay field, then the duration of the + * test may take longer if MMP writes were occurring less frequently than + * expected. 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. + * + * The mmp write period is zfs_multihost_interval / leaf-vdevs milliseconds. + * This means that 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 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 are detected. + * + * When zfs_multihost_fail_intervals = 0 then mmp write failures 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 then sequential mmp write failures will + * cause the pool to be suspended. This occurs when + * zfs_multihost_fail_intervals * zfs_multihost_interval milliseconds have + * passed since the last successful mmp write. This guarantees the activity + * test will see mmp writes if the + * pool is imported. + */ +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; +} + +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) { + dprintf("mmp_thread_start pool %s\n", + spa->spa_name); + mmp->mmp_thread = thread_create(NULL, 0, mmp_thread, + spa, 0, &p0, TS_RUN, minclsyspri); + } + 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); + + 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(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); + + 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_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("SCL_STATE acquisition took %llu ns\n", + (u_longlong_t)lock_acquire_time); + + 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) { + /* + * ZoL porting note: the following is TBD + * spa_mmp_history_set_skip(spa, mmp->mmp_kstat_id - 1); + */ + } else { + mmp->mmp_skip_error = error; + /* + * ZoL porting note: the following is TBD + * spa_mmp_history_add(spa, mmp->mmp_ub.ub_txg, + * gethrestime_sec(), mmp->mmp_delay, NULL, 0, + * mmp->mmp_kstat_id++, error); + */ + } + mutex_exit(&mmp->mmp_io_lock); + spa_config_exit(spa, SCL_STATE, mmp_tag); + return; + } + + vd = spa->spa_mmp.mmp_last_leaf; + mmp->mmp_skip_error = 0; + + if (mmp->mmp_zio_root == NULL) + mmp->mmp_zio_root = zio_root(spa, NULL, NULL, + flags | ZIO_FLAG_GODFATHER); + + ub = &mmp->mmp_ub; + ub->ub_timestamp = gethrestime_sec(); + ub->ub_mmp_magic = MMP_MAGIC; + ub->ub_mmp_delay = mmp->mmp_delay; + 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_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); + + /* + * ZoL porting note: the following is TBD + * (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 last_spa_suspended = spa_suspended(spa); + boolean_t last_spa_multihost = spa_multihost(spa); + callb_cpr_t cpr; + hrtime_t max_fail_ns = zfs_multihost_fail_intervals * + MSEC2NSEC(MAX(zfs_multihost_interval, MMP_MIN_INTERVAL)); + + mmp_thread_enter(mmp, &cpr); + + /* + * The mmp_write_done() function calculates mmp_delay based on the + * prior value of 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, but reasonable, default non-zero values. + */ + mmp->mmp_delay = MSEC2NSEC(MAX(zfs_multihost_interval, + MMP_MIN_INTERVAL)) / MAX(vdev_count_leaves(spa), 1); + mmp->mmp_last_write = gethrtime() - mmp->mmp_delay; + + while (!mmp->mmp_thread_exiting) { + uint64_t mmp_fail_intervals = zfs_multihost_fail_intervals; + uint64_t mmp_interval = MSEC2NSEC( + MAX(zfs_multihost_interval, MMP_MIN_INTERVAL)); + boolean_t suspended = spa_suspended(spa); + boolean_t multihost = spa_multihost(spa); + hrtime_t next_time; + + if (multihost) + next_time = gethrtime() + mmp_interval / + MAX(vdev_count_leaves(spa), 1); + else + next_time = gethrtime() + + MSEC2NSEC(MMP_DEFAULT_INTERVAL); + + /* + * 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)) { + mutex_enter(&mmp->mmp_io_lock); + mmp->mmp_last_write = gethrtime(); + 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); + } + last_spa_multihost = multihost; + last_spa_suspended = suspended; + + /* + * Smooth max_fail_ns when its factors are decreased, because + * making (max_fail_ns < mmp_interval) results in the pool being + * immediately suspended before writes can occur at the new + * higher frequency. + */ + if ((mmp_interval * mmp_fail_intervals) < max_fail_ns) { + max_fail_ns = ((31 * max_fail_ns) + (mmp_interval * + mmp_fail_intervals)) / 32; + } else { + max_fail_ns = mmp_interval * mmp_fail_intervals; + } + + /* + * Suspend the pool if no MMP write has succeeded in over + * mmp_interval * mmp_fail_intervals nanoseconds. + */ + if (!suspended && mmp_fail_intervals && multihost && + (gethrtime() - mmp->mmp_last_write) > max_fail_ns) { + cmn_err(CE_WARN, "MMP writes to pool '%s' have not " + "succeeded in over %llus; suspending pool", + spa_name(spa), + NSEC2SEC(gethrtime() - mmp->mmp_last_write)); + zio_suspend(spa, NULL, ZIO_SUSPEND_MMP); + } + + if (multihost && !suspended) + mmp_write_uberblock(spa); + + CALLB_CPR_SAFE_BEGIN(&cpr); + (void) cv_timedwait_sig_hrtime(&mmp->mmp_thread_cv, + &mmp->mmp_thread_lock, next_time); + 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); +} |