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Resilver restarts unnecessarily when it encounters errors

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When a resilver finishes, vdev_dtl_reassess is called to hopefully
excise DTL_MISSING (amongst other things). If there are errors during
the resilver, they are tracked in DTL_SCRUB, as spelled out in the
block comment in vdev.c. DTL_SCRUB is in-core only, so it can only
be used if the pool was online for the whole resilver. This state is
tracked with the spa_scrub_started flag, which only gets set when
the scan is initialized. Unfortunately, this flag gets cleared right
before vdev_dtl_reassess gets called, so if there are any errors
during the scan, DTL_MISSING will never get excised and the resilver
will just continually restart. This fix simply moves clearing that
flag until after the call to vdev_dtl_reasses.

In addition, if a pool is imported and already has scn_errors > 0,
this change will restart the resilver immediately instead of doing
the rest of the scan and then restarting it from the beginning. On
the other hand, if scn_errors == 0 at import, then no errors have
been encountered so far, so the spa_scrub_started flag can be safely
set.

A test has been added to verify that resilver does not restart when
relevant DTL's are available.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Paul Zuchowski <pzuchowski@datto.com>
Signed-off-by: John Poduska <jpoduska@datto.com>
Closes #10291
This commit is contained in:
John Poduska
2020-05-13 13:54:27 -04:00
committed by GitHub
parent b29e31d80d
commit 41035a0496
6 changed files with 149 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files
module/zfs/dsl_scan.c
+22 -1
View File
@@ -542,6 +542,22 @@ dsl_scan_init(dsl_pool_t *dp, uint64_t txg)
zfs_dbgmsg("new-style scrub was modified "
"by old software; restarting in txg %llu",
(longlong_t)scn->scn_restart_txg);
} else if (dsl_scan_resilvering(dp)) {
/*
* If a resilver is in progress and there are already
* errors, restart it instead of finishing this scan and
* then restarting it. If there haven't been any errors
* then remember that the incore DTL is valid.
*/
if (scn->scn_phys.scn_errors > 0) {
scn->scn_restart_txg = txg;
zfs_dbgmsg("resilver can't excise DTL_MISSING "
"when finished; restarting in txg %llu",
(u_longlong_t)scn->scn_restart_txg);
} else {
/* it's safe to excise DTL when finished */
spa->spa_scrub_started = B_TRUE;
}
}
}
@@ -887,7 +903,6 @@ dsl_scan_done(dsl_scan_t *scn, boolean_t complete, dmu_tx_t *tx)
"errors=%llu", (u_longlong_t)spa_get_errlog_size(spa));
if (DSL_SCAN_IS_SCRUB_RESILVER(scn)) {
spa->spa_scrub_started = B_FALSE;
spa->spa_scrub_active = B_FALSE;
/*
@@ -914,6 +929,12 @@ dsl_scan_done(dsl_scan_t *scn, boolean_t complete, dmu_tx_t *tx)
}
spa_errlog_rotate(spa);
/*
* Don't clear flag until after vdev_dtl_reassess to ensure that
* DTL_MISSING will get updated when possible.
*/
spa->spa_scrub_started = B_FALSE;
/*
* We may have finished replacing a device.
* Let the async thread assess this and handle the detach.