Implemented zpool scrub pause/resume

Currently, there is no way to pause a scrub. Pausing may
be useful when the pool is busy with other I/O to preserve
bandwidth.

This patch adds the ability to pause and resume scrubbing.
This is achieved by maintaining a persistent on-disk scrub state.
While the state is 'paused' we do not scrub any more blocks.
We do however perform regular scan housekeeping such as
freeing async destroyed and deadlist blocks while paused.

Reviewed by: Matthew Ahrens <[email protected]>
Reviewed by: Thomas Caputi <[email protected]>
Reviewed-by: Serapheim Dimitropoulos <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Alek Pinchuk <[email protected]>
Closes #6167

4 files changed, 166 insertions, 34 deletions

diff --git a/module/zfs/dsl_scan.c b/module/zfs/dsl_scan.c
index 89faaeb8f..ccf3cee12 100644
--- a/module/zfs/dsl_scan.c
+++ b/module/zfs/dsl_scan.c
@@ -22,6 +22,7 @@
  * Copyright (c) 2008, 2010, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2011, 2016 by Delphix. All rights reserved.
  * Copyright 2016 Gary Mills
+ * Copyright (c) 2017 Datto Inc.
  */
 
 #include <sys/dsl_scan.h>
@@ -317,6 +318,8 @@ dsl_scan_done(dsl_scan_t *scn, boolean_t complete, dmu_tx_t *tx)
 		scn->scn_phys.scn_queue_obj = 0;
 	}
 
+	scn->scn_phys.scn_flags &= ~DSF_SCRUB_PAUSED;
+
 	/*
 	 * If we were "restarted" from a stopped state, don't bother
 	 * with anything else.
@@ -403,6 +406,92 @@ dsl_scan_cancel(dsl_pool_t *dp)
 	    dsl_scan_cancel_sync, NULL, 3, ZFS_SPACE_CHECK_RESERVED));
 }
 
+boolean_t
+dsl_scan_is_paused_scrub(const dsl_scan_t *scn)
+{
+	if (dsl_scan_scrubbing(scn->scn_dp) &&
+	    scn->scn_phys.scn_flags & DSF_SCRUB_PAUSED)
+		return (B_TRUE);
+
+	return (B_FALSE);
+}
+
+static int
+dsl_scrub_pause_resume_check(void *arg, dmu_tx_t *tx)
+{
+	pool_scrub_cmd_t *cmd = arg;
+	dsl_pool_t *dp = dmu_tx_pool(tx);
+	dsl_scan_t *scn = dp->dp_scan;
+
+	if (*cmd == POOL_SCRUB_PAUSE) {
+		/* can't pause a scrub when there is no in-progress scrub */
+		if (!dsl_scan_scrubbing(dp))
+			return (SET_ERROR(ENOENT));
+
+		/* can't pause a paused scrub */
+		if (dsl_scan_is_paused_scrub(scn))
+			return (SET_ERROR(EBUSY));
+	} else if (*cmd != POOL_SCRUB_NORMAL) {
+		return (SET_ERROR(ENOTSUP));
+	}
+
+	return (0);
+}
+
+static void
+dsl_scrub_pause_resume_sync(void *arg, dmu_tx_t *tx)
+{
+	pool_scrub_cmd_t *cmd = arg;
+	dsl_pool_t *dp = dmu_tx_pool(tx);
+	spa_t *spa = dp->dp_spa;
+	dsl_scan_t *scn = dp->dp_scan;
+
+
+	if (*cmd == POOL_SCRUB_PAUSE) {
+		/* can't pause a scrub when there is no in-progress scrub */
+		spa->spa_scan_pass_scrub_pause = gethrestime_sec();
+		scn->scn_phys.scn_flags |= DSF_SCRUB_PAUSED;
+		dsl_scan_sync_state(scn, tx);
+	} else {
+		ASSERT3U(*cmd, ==, POOL_SCRUB_NORMAL);
+		if (dsl_scan_is_paused_scrub(scn)) {
+			/*
+			 * We need to keep track of how much time we spend
+			 * paused per pass so that we can adjust the scrub rate
+			 * shown in the output of 'zpool status'
+			 */
+			spa->spa_scan_pass_scrub_spent_paused +=
+			    gethrestime_sec() - spa->spa_scan_pass_scrub_pause;
+			spa->spa_scan_pass_scrub_pause = 0;
+			scn->scn_phys.scn_flags &= ~DSF_SCRUB_PAUSED;
+			dsl_scan_sync_state(scn, tx);
+		}
+	}
+}
+
+/*
+ * Set scrub pause/resume state if it makes sense to do so
+ */
+int
+dsl_scrub_set_pause_resume(const dsl_pool_t *dp, pool_scrub_cmd_t cmd)
+{
+	return (dsl_sync_task(spa_name(dp->dp_spa),
+	    dsl_scrub_pause_resume_check, dsl_scrub_pause_resume_sync, &cmd, 3,
+	    ZFS_SPACE_CHECK_RESERVED));
+}
+
+boolean_t
+dsl_scan_scrubbing(const dsl_pool_t *dp)
+{
+	dsl_scan_t *scn = dp->dp_scan;
+
+	if (scn->scn_phys.scn_state == DSS_SCANNING &&
+	    scn->scn_phys.scn_func == POOL_SCAN_SCRUB)
+		return (B_TRUE);
+
+	return (B_FALSE);
+}
+
 static void dsl_scan_visitbp(blkptr_t *bp, const zbookmark_phys_t *zb,
     dnode_phys_t *dnp, dsl_dataset_t *ds, dsl_scan_t *scn,
     dmu_objset_type_t ostype, dmu_tx_t *tx);
@@ -444,7 +533,7 @@ dsl_scan_sync_state(dsl_scan_t *scn, dmu_tx_t *tx)
 extern int zfs_vdev_async_write_active_min_dirty_percent;
 
 static boolean_t
-dsl_scan_check_pause(dsl_scan_t *scn, const zbookmark_phys_t *zb)
+dsl_scan_check_suspend(dsl_scan_t *scn, const zbookmark_phys_t *zb)
 {
 	uint64_t elapsed_nanosecs;
 	int mintime;
@@ -454,8 +543,8 @@ dsl_scan_check_pause(dsl_scan_t *scn, const zbookmark_phys_t *zb)
 	if (zb && (int64_t)zb->zb_object < 0)
 		return (B_FALSE);
 
-	if (scn->scn_pausing)
-		return (B_TRUE); /* we're already pausing */
+	if (scn->scn_suspending)
+		return (B_TRUE); /* we're already suspending */
 
 	if (!ZB_IS_ZERO(&scn->scn_phys.scn_bookmark))
 		return (B_FALSE); /* we're resuming */
@@ -465,7 +554,7 @@ dsl_scan_check_pause(dsl_scan_t *scn, const zbookmark_phys_t *zb)
 		return (B_FALSE);
 
 	/*
-	 * We pause if:
+	 * We suspend if:
 	 *  - we have scanned for the maximum time: an entire txg
 	 *    timeout (default 5 sec)
 	 *  or
@@ -488,19 +577,19 @@ dsl_scan_check_pause(dsl_scan_t *scn, const zbookmark_phys_t *zb)
 	    dirty_pct >= zfs_vdev_async_write_active_min_dirty_percent)) ||
 	    spa_shutting_down(scn->scn_dp->dp_spa)) {
 		if (zb) {
-			dprintf("pausing at bookmark %llx/%llx/%llx/%llx\n",
+			dprintf("suspending at bookmark %llx/%llx/%llx/%llx\n",
 			    (longlong_t)zb->zb_objset,
 			    (longlong_t)zb->zb_object,
 			    (longlong_t)zb->zb_level,
 			    (longlong_t)zb->zb_blkid);
 			scn->scn_phys.scn_bookmark = *zb;
 		}
-		dprintf("pausing at DDT bookmark %llx/%llx/%llx/%llx\n",
+		dprintf("suspending at DDT bookmark %llx/%llx/%llx/%llx\n",
 		    (longlong_t)scn->scn_phys.scn_ddt_bookmark.ddb_class,
 		    (longlong_t)scn->scn_phys.scn_ddt_bookmark.ddb_type,
 		    (longlong_t)scn->scn_phys.scn_ddt_bookmark.ddb_checksum,
 		    (longlong_t)scn->scn_phys.scn_ddt_bookmark.ddb_cursor);
-		scn->scn_pausing = B_TRUE;
+		scn->scn_suspending = B_TRUE;
 		return (B_TRUE);
 	}
 	return (B_FALSE);
@@ -638,7 +727,7 @@ dsl_scan_check_resume(dsl_scan_t *scn, const dnode_phys_t *dnp,
 		/*
 		 * If we found the block we're trying to resume from, or
 		 * we went past it to a different object, zero it out to
-		 * indicate that it's OK to start checking for pausing
+		 * indicate that it's OK to start checking for suspending
 		 * again.
 		 */
 		if (bcmp(zb, &scn->scn_phys.scn_bookmark, sizeof (*zb)) == 0 ||
@@ -745,7 +834,7 @@ dsl_scan_recurse(dsl_scan_t *scn, dsl_dataset_t *ds, dmu_objset_type_t ostype,
 			/*
 			 * We also always visit user/group accounting
 			 * objects, and never skip them, even if we are
-			 * pausing.  This is necessary so that the space
+			 * suspending.  This is necessary so that the space
 			 * deltas from this txg get integrated.
 			 */
 			dsl_scan_visitdnode(scn, ds, osp->os_type,
@@ -803,7 +892,7 @@ dsl_scan_visitbp(blkptr_t *bp, const zbookmark_phys_t *zb,
 
 	/* ASSERT(pbuf == NULL || arc_released(pbuf)); */
 
-	if (dsl_scan_check_pause(scn, zb))
+	if (dsl_scan_check_suspend(scn, zb))
 		goto out;
 
 	if (dsl_scan_check_resume(scn, dnp, zb))
@@ -1149,14 +1238,14 @@ dsl_scan_visitds(dsl_scan_t *scn, uint64_t dsobj, dmu_tx_t *tx)
 	dsname = kmem_alloc(ZFS_MAX_DATASET_NAME_LEN, KM_SLEEP);
 	dsl_dataset_name(ds, dsname);
 	zfs_dbgmsg("scanned dataset %llu (%s) with min=%llu max=%llu; "
-	    "pausing=%u",
+	    "suspending=%u",
 	    (longlong_t)dsobj, dsname,
 	    (longlong_t)scn->scn_phys.scn_cur_min_txg,
 	    (longlong_t)scn->scn_phys.scn_cur_max_txg,
-	    (int)scn->scn_pausing);
+	    (int)scn->scn_suspending);
 	kmem_free(dsname, ZFS_MAX_DATASET_NAME_LEN);
 
-	if (scn->scn_pausing)
+	if (scn->scn_suspending)
 		goto out;
 
 	/*
@@ -1322,13 +1411,13 @@ dsl_scan_ddt(dsl_scan_t *scn, dmu_tx_t *tx)
 		dsl_scan_ddt_entry(scn, ddb->ddb_checksum, &dde, tx);
 		n++;
 
-		if (dsl_scan_check_pause(scn, NULL))
+		if (dsl_scan_check_suspend(scn, NULL))
 			break;
 	}
 
-	zfs_dbgmsg("scanned %llu ddt entries with class_max = %u; pausing=%u",
-	    (longlong_t)n, (int)scn->scn_phys.scn_ddt_class_max,
-	    (int)scn->scn_pausing);
+	zfs_dbgmsg("scanned %llu ddt entries with class_max = %u; "
+	    "suspending=%u", (longlong_t)n,
+	    (int)scn->scn_phys.scn_ddt_class_max, (int)scn->scn_suspending);
 
 	ASSERT(error == 0 || error == ENOENT);
 	ASSERT(error != ENOENT ||
@@ -1372,7 +1461,7 @@ dsl_scan_visit(dsl_scan_t *scn, dmu_tx_t *tx)
 		scn->scn_phys.scn_cur_min_txg = scn->scn_phys.scn_min_txg;
 		scn->scn_phys.scn_cur_max_txg = scn->scn_phys.scn_max_txg;
 		dsl_scan_ddt(scn, tx);
-		if (scn->scn_pausing)
+		if (scn->scn_suspending)
 			return;
 	}
 
@@ -1384,7 +1473,7 @@ dsl_scan_visit(dsl_scan_t *scn, dmu_tx_t *tx)
 		dsl_scan_visit_rootbp(scn, NULL,
 		    &dp->dp_meta_rootbp, tx);
 		spa_set_rootblkptr(dp->dp_spa, &dp->dp_meta_rootbp);
-		if (scn->scn_pausing)
+		if (scn->scn_suspending)
 			return;
 
 		if (spa_version(dp->dp_spa) < SPA_VERSION_DSL_SCRUB) {
@@ -1394,22 +1483,22 @@ dsl_scan_visit(dsl_scan_t *scn, dmu_tx_t *tx)
 			dsl_scan_visitds(scn,
 			    dp->dp_origin_snap->ds_object, tx);
 		}
-		ASSERT(!scn->scn_pausing);
+		ASSERT(!scn->scn_suspending);
 	} else if (scn->scn_phys.scn_bookmark.zb_objset !=
 	    ZB_DESTROYED_OBJSET) {
 		/*
-		 * If we were paused, continue from here.  Note if the
-		 * ds we were paused on was deleted, the zb_objset may
+		 * If we were suspended, continue from here.  Note if the
+		 * ds we were suspended on was deleted, the zb_objset may
 		 * be -1, so we will skip this and find a new objset
 		 * below.
 		 */
 		dsl_scan_visitds(scn, scn->scn_phys.scn_bookmark.zb_objset, tx);
-		if (scn->scn_pausing)
+		if (scn->scn_suspending)
 			return;
 	}
 
 	/*
-	 * In case we were paused right at the end of the ds, zero the
+	 * In case we were suspended right at the end of the ds, zero the
 	 * bookmark so we don't think that we're still trying to resume.
 	 */
 	bzero(&scn->scn_phys.scn_bookmark, sizeof (zbookmark_phys_t));
@@ -1443,7 +1532,7 @@ dsl_scan_visit(dsl_scan_t *scn, dmu_tx_t *tx)
 
 		dsl_scan_visitds(scn, dsobj, tx);
 		zap_cursor_fini(zc);
-		if (scn->scn_pausing)
+		if (scn->scn_suspending)
 			goto out;
 	}
 	zap_cursor_fini(zc);
@@ -1453,7 +1542,7 @@ out:
 }
 
 static boolean_t
-dsl_scan_free_should_pause(dsl_scan_t *scn)
+dsl_scan_free_should_suspend(dsl_scan_t *scn)
 {
 	uint64_t elapsed_nanosecs;
 
@@ -1477,7 +1566,7 @@ dsl_scan_free_block_cb(void *arg, const blkptr_t *bp, dmu_tx_t *tx)
 
 	if (!scn->scn_is_bptree ||
 	    (BP_GET_LEVEL(bp) == 0 && BP_GET_TYPE(bp) != DMU_OT_OBJSET)) {
-		if (dsl_scan_free_should_pause(scn))
+		if (dsl_scan_free_should_suspend(scn))
 			return (SET_ERROR(ERESTART));
 	}
 
@@ -1500,7 +1589,8 @@ dsl_scan_active(dsl_scan_t *scn)
 		return (B_FALSE);
 	if (spa_shutting_down(spa))
 		return (B_FALSE);
-	if (scn->scn_phys.scn_state == DSS_SCANNING ||
+	if ((scn->scn_phys.scn_state == DSS_SCANNING &&
+	    !dsl_scan_is_paused_scrub(scn)) ||
 	    (scn->scn_async_destroying && !scn->scn_async_stalled))
 		return (B_TRUE);
 
@@ -1555,12 +1645,12 @@ dsl_scan_sync(dsl_pool_t *dp, dmu_tx_t *tx)
 		return;
 
 	scn->scn_visited_this_txg = 0;
-	scn->scn_pausing = B_FALSE;
+	scn->scn_suspending = B_FALSE;
 	scn->scn_sync_start_time = gethrtime();
 	spa->spa_scrub_active = B_TRUE;
 
 	/*
-	 * First process the async destroys.  If we pause, don't do
+	 * First process the async destroys.  If we suspend, don't do
 	 * any scrubbing or resilvering.  This ensures that there are no
 	 * async destroys while we are scanning, so the scan code doesn't
 	 * have to worry about traversing it.  It is also faster to free the
@@ -1677,7 +1767,7 @@ dsl_scan_sync(dsl_pool_t *dp, dmu_tx_t *tx)
 		return;
 
 	if (scn->scn_done_txg == tx->tx_txg) {
-		ASSERT(!scn->scn_pausing);
+		ASSERT(!scn->scn_suspending);
 		/* finished with scan. */
 		zfs_dbgmsg("txg %llu scan complete", tx->tx_txg);
 		dsl_scan_done(scn, B_TRUE, tx);
@@ -1686,6 +1776,9 @@ dsl_scan_sync(dsl_pool_t *dp, dmu_tx_t *tx)
 		return;
 	}
 
+	if (dsl_scan_is_paused_scrub(scn))
+		return;
+
 	if (scn->scn_phys.scn_ddt_bookmark.ddb_class <=
 	    scn->scn_phys.scn_ddt_class_max) {
 		zfs_dbgmsg("doing scan sync txg %llu; "
@@ -1720,7 +1813,7 @@ dsl_scan_sync(dsl_pool_t *dp, dmu_tx_t *tx)
 	    (longlong_t)scn->scn_visited_this_txg,
 	    (longlong_t)NSEC2MSEC(gethrtime() - scn->scn_sync_start_time));
 
-	if (!scn->scn_pausing) {
+	if (!scn->scn_suspending) {
 		scn->scn_done_txg = tx->tx_txg + 1;
 		zfs_dbgmsg("txg %llu traversal complete, waiting till txg %llu",
 		    tx->tx_txg, scn->scn_done_txg);
@@ -1957,11 +2050,15 @@ dsl_scan_scrub_cb(dsl_pool_t *dp,
 	return (0);
 }
 
-/* Called by the ZFS_IOC_POOL_SCAN ioctl to start a scrub or resilver */
+/*
+ * Called by the ZFS_IOC_POOL_SCAN ioctl to start a scrub or resilver.
+ * Can also be called to resume a paused scrub.
+ */
 int
 dsl_scan(dsl_pool_t *dp, pool_scan_func_t func)
 {
 	spa_t *spa = dp->dp_spa;
+	dsl_scan_t *scn = dp->dp_scan;
 
 	/*
 	 * Purge all vdev caches and probe all devices.  We do this here
@@ -1976,6 +2073,16 @@ dsl_scan(dsl_pool_t *dp, pool_scan_func_t func)
 	spa->spa_scrub_reopen = B_FALSE;
 	(void) spa_vdev_state_exit(spa, NULL, 0);
 
+	if (func == POOL_SCAN_SCRUB && dsl_scan_is_paused_scrub(scn)) {
+		/* got scrub start cmd, resume paused scrub */
+		int err = dsl_scrub_set_pause_resume(scn->scn_dp,
+		    POOL_SCRUB_NORMAL);
+		if (err == 0)
+			return (ECANCELED);
+
+		return (SET_ERROR(err));
+	}
+
 	return (dsl_sync_task(spa_name(spa), dsl_scan_setup_check,
 	    dsl_scan_setup_sync, &func, 0, ZFS_SPACE_CHECK_NONE));
 }
diff --git a/module/zfs/spa.c b/module/zfs/spa.c
index 031535321..d759ce718 100644
--- a/module/zfs/spa.c
+++ b/module/zfs/spa.c
@@ -29,6 +29,7 @@
  * Copyright (c) 2014 Integros [integros.com]
  * Copyright 2016 Toomas Soome <[email protected]>
  * Copyright (c) 2016 Actifio, Inc. All rights reserved.
+ * Copyright (c) 2017 Datto Inc.
  */
 
 /*
@@ -5726,6 +5727,16 @@ spa_vdev_setfru(spa_t *spa, uint64_t guid, const char *newfru)
  * SPA Scanning
  * ==========================================================================
  */
+int
+spa_scrub_pause_resume(spa_t *spa, pool_scrub_cmd_t cmd)
+{
+	ASSERT(spa_config_held(spa, SCL_ALL, RW_WRITER) == 0);
+
+	if (dsl_scan_resilvering(spa->spa_dsl_pool))
+		return (SET_ERROR(EBUSY));
+
+	return (dsl_scrub_set_pause_resume(spa->spa_dsl_pool, cmd));
+}
 
 int
 spa_scan_stop(spa_t *spa)
diff --git a/module/zfs/spa_misc.c b/module/zfs/spa_misc.c
index fb425e121..8e23bcf45 100644
--- a/module/zfs/spa_misc.c
+++ b/module/zfs/spa_misc.c
@@ -24,6 +24,7 @@
  * Copyright 2015 Nexenta Systems, Inc.  All rights reserved.
  * Copyright (c) 2014 Spectra Logic Corporation, All rights reserved.
  * Copyright 2013 Saso Kiselkov. All rights reserved.
+ * Copyright (c) 2017 Datto Inc.
  */
 
 #include <sys/zfs_context.h>
@@ -2007,6 +2008,11 @@ spa_scan_stat_init(spa_t *spa)
 {
 	/* data not stored on disk */
 	spa->spa_scan_pass_start = gethrestime_sec();
+	if (dsl_scan_is_paused_scrub(spa->spa_dsl_pool->dp_scan))
+		spa->spa_scan_pass_scrub_pause = spa->spa_scan_pass_start;
+	else
+		spa->spa_scan_pass_scrub_pause = 0;
+	spa->spa_scan_pass_scrub_spent_paused = 0;
 	spa->spa_scan_pass_exam = 0;
 	vdev_scan_stat_init(spa->spa_root_vdev);
 }
@@ -2037,6 +2043,8 @@ spa_scan_get_stats(spa_t *spa, pool_scan_stat_t *ps)
 	/* data not stored on disk */
 	ps->pss_pass_start = spa->spa_scan_pass_start;
 	ps->pss_pass_exam = spa->spa_scan_pass_exam;
+	ps->pss_pass_scrub_pause = spa->spa_scan_pass_scrub_pause;
+	ps->pss_pass_scrub_spent_paused = spa->spa_scan_pass_scrub_spent_paused;
 
 	return (0);
 }
diff --git a/module/zfs/zfs_ioctl.c b/module/zfs/zfs_ioctl.c
index fff1a3c06..acdfba173 100644
--- a/module/zfs/zfs_ioctl.c
+++ b/module/zfs/zfs_ioctl.c
@@ -1674,6 +1674,7 @@ zfs_ioc_pool_tryimport(zfs_cmd_t *zc)
  * inputs:
  * zc_name              name of the pool
  * zc_cookie            scan func (pool_scan_func_t)
+ * zc_flags             scrub pause/resume flag (pool_scrub_cmd_t)
  */
 static int
 zfs_ioc_pool_scan(zfs_cmd_t *zc)
@@ -1684,7 +1685,12 @@ zfs_ioc_pool_scan(zfs_cmd_t *zc)
 	if ((error = spa_open(zc->zc_name, &spa, FTAG)) != 0)
 		return (error);
 
-	if (zc->zc_cookie == POOL_SCAN_NONE)
+	if (zc->zc_flags >= POOL_SCRUB_FLAGS_END)
+		return (SET_ERROR(EINVAL));
+
+	if (zc->zc_flags == POOL_SCRUB_PAUSE)
+		error = spa_scrub_pause_resume(spa, POOL_SCRUB_PAUSE);
+	else if (zc->zc_cookie == POOL_SCAN_NONE)
 		error = spa_scan_stop(spa);
 	else
 		error = spa_scan(spa, zc->zc_cookie);