Author: mav
Date: Wed Feb 26 15:45:04 2020
New Revision: 358336
URL: https://svnweb.freebsd.org/changeset/base/358336
Log:
MFZoL: Fix txg_sync_thread hang in scan_exec_io()
When scn->scn_maxinflight_bytes has not been initialized it's
possible to hang on the condition variable in scan_exec_io().
This issue was uncovered by ztest and is only possible when
deduplication is enabled through the following call path.
txg_sync_thread()
spa_sync()
ddt_sync_table()
ddt_sync_entry()
dsl_scan_ddt_entry()
dsl_scan_scrub_cb()
dsl_scan_enqueuei()
scan_exec_io()
cv_wait()
Resolve the issue by always initializing scn_maxinflight_bytes
to a reasonable minimum value. This value will be recalculated
in dsl_scan_sync() to pick up changes to zfs_scan_vdev_limit
and the addition/removal of vdevs.
Reviewed-by: Tom Caputi <tcap...@datto.com>
Reviewed by: George Melikov <m...@gmelikov.ru>
Signed-off-by: Brian Behlendorf <behlendo...@llnl.gov>
Closes #7098
zfsonlinux/zfs@f90a30ad1b32a971f62a540f8944e42f99b254ce
MFC after: 1 week
Modified:
head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_scan.c
Modified: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_scan.c
==============================================================================
--- head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_scan.c Wed Feb
26 15:15:55 2020 (r358335)
+++ head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_scan.c Wed Feb
26 15:45:04 2020 (r358336)
@@ -125,6 +125,7 @@ static boolean_t scan_ds_queue_contains(dsl_scan_t *sc
static void scan_ds_queue_insert(dsl_scan_t *scn, uint64_t dsobj, uint64_t
txg);
static void scan_ds_queue_remove(dsl_scan_t *scn, uint64_t dsobj);
static void scan_ds_queue_sync(dsl_scan_t *scn, dmu_tx_t *tx);
+static uint64_t dsl_scan_count_leaves(vdev_t *vd);
extern int zfs_vdev_async_write_active_min_dirty_percent;
@@ -439,6 +440,14 @@ dsl_scan_init(dsl_pool_t *dp, uint64_t txg)
scn->scn_async_destroying = spa_feature_is_active(dp->dp_spa,
SPA_FEATURE_ASYNC_DESTROY);
+ /*
+ * Calculate the max number of in-flight bytes for pool-wide
+ * scanning operations (minimum 1MB). Limits for the issuing
+ * phase are done per top-level vdev and are handled separately.
+ */
+ scn->scn_maxinflight_bytes = MAX(zfs_scan_vdev_limit *
+ dsl_scan_count_leaves(spa->spa_root_vdev), 1ULL << 20);
+
bcopy(&scn->scn_phys, &scn->scn_phys_cached, sizeof (scn->scn_phys));
avl_create(&scn->scn_queue, scan_ds_queue_compare, sizeof (scan_ds_t),
offsetof(scan_ds_t, sds_node));
@@ -2350,7 +2359,7 @@ dsl_scan_ddt_entry(dsl_scan_t *scn, enum zio_checksum
zbookmark_phys_t zb = { 0 };
int p;
- if (scn->scn_phys.scn_state != DSS_SCANNING)
+ if (!dsl_scan_is_running(scn))
return;
for (p = 0; p < DDT_PHYS_TYPES; p++, ddp++) {
@@ -3333,7 +3342,7 @@ dsl_scan_sync(dsl_pool_t *dp, dmu_tx_t *tx)
uint64_t nr_leaves = dsl_scan_count_leaves(spa->spa_root_vdev);
/*
- * Calculate the max number of in-flight bytes for pool-wide
+ * Recalculate the max number of in-flight bytes for pool-wide
* scanning operations (minimum 1MB). Limits for the issuing
* phase are done per top-level vdev and are handled separately.
*/
@@ -3652,6 +3661,8 @@ dsl_scan_scrub_done(zio_t *zio)
dsl_scan_io_queue_t *queue = zio->io_private;
abd_free(zio->io_abd);
+
+ ASSERT3U(scn->scn_maxinflight_bytes, >, 0);
if (queue == NULL) {
mutex_enter(&spa->spa_scrub_lock);
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