svn commit: r309250 - head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs
Andriy Gapon
avg at FreeBSD.org
Mon Nov 28 15:14:32 UTC 2016
Author: avg
Date: Mon Nov 28 15:14:31 2016
New Revision: 309250
URL: https://svnweb.freebsd.org/changeset/base/309250
Log:
MFV r309249: 3821 Race in rollback, zil close, and zil flush
Note: there was a merge conflict resolved by me.
illumos/illumos-gate at 43297f973a3543e7403ac27076490ab958a94b15
https://github.com/illumos/illumos-gate/commit/43297f973a3543e7403ac27076490ab958a94b15
https://www.illumos.org/issues/3821
We recently had nodes with some of the latest zfs bits panic on us in a
rollback-heavy environment. The following is from my preliminary analysis:
Let's look at where we died:
> $C
ffffff01ea6b9a10 taskq_dispatch+0x3a(0, fffffffff7d20450, ffffff5551dea920, 1)
ffffff01ea6b9a60 zil_clean+0xce(ffffff4b7106c080, 7e0f1)
ffffff01ea6b9aa0 dsl_pool_sync_done+0x47(ffffff4313065680, 7e0f1)
ffffff01ea6b9b70 spa_sync+0x55f(ffffff4310c1d040, 7e0f1)
ffffff01ea6b9c20 txg_sync_thread+0x20f(ffffff4313065680)
ffffff01ea6b9c30 thread_start+8()
If we dig in we can find that this dataset corresponds to a zone:
> ffffff4b7106c080::print zilog_t zl_os->os_dsl_dataset->ds_dir->dd_myname
zl_os->os_dsl_dataset->ds_dir->dd_myname = [ "8ffce16a-13c2-4efa-a233-
9e378e89877b" ]
Okay so we have a null taskq pointer. That only happens during the calls to
zil_open and zil_close. If we poke around we can see that we're actually in
midst of a rollback:
> ::pgrep zfs | ::printf "0x%x %s\\n" proc_t . p_user.u_psargs
0xffffff43262800a0 zfs rollback zones/15714eb6-f5ea-469f-ac6d-
4b8ab06213c2 at marlin_init
0xffffff54e22a1028 zfs rollback zones/8ffce16a-13c2-4efa-a233-
9e378e89877b at marlin_init
0xffffff4362f3a058 zfs rollback zones/0ddb8e49-ca7e-42e1-8fdc-
4ac4ba8fe9f8 at marlin_init
0xffffff5748e8d020 zfs rollback zones/426357b5-832d-4430-953e-
10cd45ff8e9f at marlin_init
0xffffff436b867008 zfs rollback zones/8f36bf37-8a9c-4a44-995c-
6d1b2751e6f5 at marlin_init
0xffffff4381ad4090 zfs rollback zones/6c8eca18-fbd6-46dd-ac24-
2ed45cd0da70 at marlin_init
Reviewed by: Matthew Ahrens <mahrens at delphix.com>
Reviewed by: Dan Kimmel <dan.kimmel at delphix.com>
Reviewed by: Pavel Zakharov <pavel.zakharov at delphix.com>
Reviewed by: Andriy Gapon <avg at FreeBSD.org>
Approved by: Richard Lowe <richlowe at richlowe.net>
Author: George Wilson <george.wilson at delphix.com>
MFC after: 3 weeks
Modified:
head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_pool.c
head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/spa.c
head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zil.c
Directory Properties:
head/sys/cddl/contrib/opensolaris/ (props changed)
Modified: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_pool.c
==============================================================================
--- head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_pool.c Mon Nov 28 15:09:58 2016 (r309249)
+++ head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_pool.c Mon Nov 28 15:14:31 2016 (r309250)
@@ -20,7 +20,7 @@
*/
/*
* Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2011, 2015 by Delphix. All rights reserved.
+ * Copyright (c) 2011, 2016 by Delphix. All rights reserved.
* Copyright (c) 2013 Steven Hartland. All rights reserved.
* Copyright (c) 2014 Spectra Logic Corporation, All rights reserved.
* Copyright (c) 2014 Integros [integros.com]
@@ -681,9 +681,16 @@ dsl_pool_sync_done(dsl_pool_t *dp, uint6
{
zilog_t *zilog;
- while (zilog = txg_list_remove(&dp->dp_dirty_zilogs, txg)) {
+ while (zilog = txg_list_head(&dp->dp_dirty_zilogs, txg)) {
dsl_dataset_t *ds = dmu_objset_ds(zilog->zl_os);
+ /*
+ * We don't remove the zilog from the dp_dirty_zilogs
+ * list until after we've cleaned it. This ensures that
+ * callers of zilog_is_dirty() receive an accurate
+ * answer when they are racing with the spa sync thread.
+ */
zil_clean(zilog, txg);
+ (void) txg_list_remove_this(&dp->dp_dirty_zilogs, zilog, txg);
ASSERT(!dmu_objset_is_dirty(zilog->zl_os, txg));
dmu_buf_rele(ds->ds_dbuf, zilog);
}
Modified: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/spa.c
==============================================================================
--- head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/spa.c Mon Nov 28 15:09:58 2016 (r309249)
+++ head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/spa.c Mon Nov 28 15:14:31 2016 (r309250)
@@ -7086,8 +7086,6 @@ spa_sync(spa_t *spa, uint64_t txg)
spa->spa_config_syncing = NULL;
}
- spa->spa_ubsync = spa->spa_uberblock;
-
dsl_pool_sync_done(dp, txg);
mutex_enter(&spa->spa_alloc_lock);
@@ -7112,6 +7110,13 @@ spa_sync(spa_t *spa, uint64_t txg)
spa->spa_sync_pass = 0;
+ /*
+ * Update the last synced uberblock here. We want to do this at
+ * the end of spa_sync() so that consumers of spa_last_synced_txg()
+ * will be guaranteed that all the processing associated with
+ * that txg has been completed.
+ */
+ spa->spa_ubsync = spa->spa_uberblock;
spa_config_exit(spa, SCL_CONFIG, FTAG);
spa_handle_ignored_writes(spa);
Modified: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zil.c
==============================================================================
--- head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zil.c Mon Nov 28 15:09:58 2016 (r309249)
+++ head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zil.c Mon Nov 28 15:14:31 2016 (r309250)
@@ -20,8 +20,7 @@
*/
/*
* Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2011, 2015 by Delphix. All rights reserved.
- * Copyright (c) 2011, 2014 by Delphix. All rights reserved.
+ * Copyright (c) 2011, 2016 by Delphix. All rights reserved.
* Copyright (c) 2014 Integros [integros.com]
*/
@@ -502,6 +501,27 @@ zilog_dirty(zilog_t *zilog, uint64_t txg
}
}
+/*
+ * Determine if the zil is dirty in the specified txg. Callers wanting to
+ * ensure that the dirty state does not change must hold the itxg_lock for
+ * the specified txg. Holding the lock will ensure that the zil cannot be
+ * dirtied (zil_itx_assign) or cleaned (zil_clean) while we check its current
+ * state.
+ */
+boolean_t
+zilog_is_dirty_in_txg(zilog_t *zilog, uint64_t txg)
+{
+ dsl_pool_t *dp = zilog->zl_dmu_pool;
+
+ if (txg_list_member(&dp->dp_dirty_zilogs, zilog, txg & TXG_MASK))
+ return (B_TRUE);
+ return (B_FALSE);
+}
+
+/*
+ * Determine if the zil is dirty. The zil is considered dirty if it has
+ * any pending itx records that have not been cleaned by zil_clean().
+ */
boolean_t
zilog_is_dirty(zilog_t *zilog)
{
@@ -1062,8 +1082,6 @@ zil_lwb_commit(zilog_t *zilog, itx_t *it
return (NULL);
ASSERT(lwb->lwb_buf != NULL);
- ASSERT(zilog_is_dirty(zilog) ||
- spa_freeze_txg(zilog->zl_spa) != UINT64_MAX);
if (lrc->lrc_txtype == TX_WRITE && itx->itx_wr_state == WR_NEED_COPY)
dlen = P2ROUNDUP_TYPED(
@@ -1401,6 +1419,11 @@ zil_get_commit_list(zilog_t *zilog)
else
otxg = spa_last_synced_txg(zilog->zl_spa) + 1;
+ /*
+ * This is inherently racy, since there is nothing to prevent
+ * the last synced txg from changing. That's okay since we'll
+ * only commit things in the future.
+ */
for (txg = otxg; txg < (otxg + TXG_CONCURRENT_STATES); txg++) {
itxg_t *itxg = &zilog->zl_itxg[txg & TXG_MASK];
@@ -1410,6 +1433,16 @@ zil_get_commit_list(zilog_t *zilog)
continue;
}
+ /*
+ * If we're adding itx records to the zl_itx_commit_list,
+ * then the zil better be dirty in this "txg". We can assert
+ * that here since we're holding the itxg_lock which will
+ * prevent spa_sync from cleaning it. Once we add the itxs
+ * to the zl_itx_commit_list we must commit it to disk even
+ * if it's unnecessary (i.e. the txg was synced).
+ */
+ ASSERT(zilog_is_dirty_in_txg(zilog, txg) ||
+ spa_freeze_txg(zilog->zl_spa) != UINT64_MAX);
list_move_tail(commit_list, &itxg->itxg_itxs->i_sync_list);
mutex_exit(&itxg->itxg_lock);
@@ -1432,6 +1465,10 @@ zil_async_to_sync(zilog_t *zilog, uint64
else
otxg = spa_last_synced_txg(zilog->zl_spa) + 1;
+ /*
+ * This is inherently racy, since there is nothing to prevent
+ * the last synced txg from changing.
+ */
for (txg = otxg; txg < (otxg + TXG_CONCURRENT_STATES); txg++) {
itxg_t *itxg = &zilog->zl_itxg[txg & TXG_MASK];
@@ -1503,8 +1540,14 @@ zil_commit_writer(zilog_t *zilog)
DTRACE_PROBE1(zil__cw1, zilog_t *, zilog);
while (itx = list_head(&zilog->zl_itx_commit_list)) {
txg = itx->itx_lr.lrc_txg;
- ASSERT(txg);
+ ASSERT3U(txg, !=, 0);
+ /*
+ * This is inherently racy and may result in us writing
+ * out a log block for a txg that was just synced. This is
+ * ok since we'll end cleaning up that log block the next
+ * time we call zil_sync().
+ */
if (txg > spa_last_synced_txg(spa) || txg > spa_freeze_txg(spa))
lwb = zil_lwb_commit(zilog, itx, lwb);
list_remove(&zilog->zl_itx_commit_list, itx);
@@ -1821,7 +1864,10 @@ zil_close(zilog_t *zilog)
mutex_exit(&zilog->zl_lock);
if (txg)
txg_wait_synced(zilog->zl_dmu_pool, txg);
- ASSERT(!zilog_is_dirty(zilog));
+
+ if (zilog_is_dirty(zilog))
+ zfs_dbgmsg("zil (%p) is dirty, txg %llu", zilog, txg);
+ VERIFY(!zilog_is_dirty(zilog));
taskq_destroy(zilog->zl_clean_taskq);
zilog->zl_clean_taskq = NULL;
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