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3821 Race in rollback, zil close, and zil flush

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illumos/illumos-gate@43297f973a
43297f973a

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@marlin_init
  0xffffff54e22a1028 zfs rollback zones/8ffce16a-13c2-4efa-a233-
  9e378e89877b@marlin_init
  0xffffff4362f3a058 zfs rollback zones/0ddb8e49-ca7e-42e1-8fdc-
  4ac4ba8fe9f8@marlin_init
  0xffffff5748e8d020 zfs rollback zones/426357b5-832d-4430-953e-
  10cd45ff8e9f@marlin_init
  0xffffff436b867008 zfs rollback zones/8f36bf37-8a9c-4a44-995c-
  6d1b2751e6f5@marlin_init
  0xffffff4381ad4090 zfs rollback zones/6c8eca18-fbd6-46dd-ac24-
  2ed45cd0da70@marlin_init

Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Dan Kimmel <dan.kimmel@delphix.com>
Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com>
Reviewed by: Andriy Gapon <avg@FreeBSD.org>
Approved by: Richard Lowe <richlowe@richlowe.net>
Author: George Wilson <george.wilson@delphix.com>
This commit is contained in:
Andriy Gapon 2016-11-28 15:09:58 +00:00
parent aee4554721
commit aed3e94d2f
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/vendor-sys/illumos/dist/; revision=309249
3 changed files with 70 additions and 10 deletions
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11
uts/common/fs/zfs/dsl_pool.c
View File

@ -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]
@ -581,9 +581,16 @@ dsl_pool_sync_done(dsl_pool_t *dp, uint64_t txg)
{
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);
}

9
uts/common/fs/zfs/spa.c
View File

@ -6735,8 +6735,6 @@ 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);
@ -6761,6 +6759,13 @@ 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);

60
uts/common/fs/zfs/zil.c
View File

@ -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]
*/
@ -485,6 +484,27 @@ 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)
{
@ -1048,8 +1068,6 @@ zil_lwb_commit(zilog_t *zilog, itx_t *itx, lwb_t *lwb)
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(
@ -1285,6 +1303,8 @@ zil_itx_assign(zilog_t *zilog, itx_t *itx, dmu_tx_t *tx)
* this itxg. Save the itxs for release below.
* This should be rare.
*/
zfs_dbgmsg("zil_itx_assign: missed itx cleanup for "
"txg %llu", itxg->itxg_txg);
atomic_add_64(&zilog->zl_itx_list_sz, -itxg->itxg_sod);
itxg->itxg_sod = 0;
clean = itxg->itxg_itxs;
@ -1382,6 +1402,11 @@ 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];
@ -1391,6 +1416,16 @@ 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);
push_sod += itxg->itxg_sod;
itxg->itxg_sod = 0;
@ -1416,6 +1451,10 @@ zil_async_to_sync(zilog_t *zilog, uint64_t foid)
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];
@ -1487,8 +1526,14 @@ 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);
@ -1805,7 +1850,10 @@ 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;