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Prevent ZFS leaking pool free space

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When processing async destroys ZFS would leak space every txg timeout
(5 seconds by default), if no writes occurred, until the pool is totally
full. At this point it would be unfixable without a pool recreation.

In addition if the machine was rebooted with the pool in this situation
would fail to import on boot, hanging indefinitely, as the import process
requires the ability to write data to the pool. Any attempts to query the
pool status during the hung import would not return as the import holds
the pool lock.

The only way to import such a pool would be to specify -o readonly=on
to the zpool import.

zdb -bb <pool> can be used to check for "deferred free" size which is where
this lost space will be counted.

MFC after:	3 days
Sponsored by:	Multiplay
This commit is contained in:
Steven Hartland 2014-10-16 02:23:27 +00:00
parent bbcf1f62b6
commit ca6505b818
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=273158
1 changed files with 8 additions and 7 deletions
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15
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_scan.c
View File

@ -1459,13 +1459,6 @@ dsl_scan_sync(dsl_pool_t *dp, dmu_tx_t *tx)
"traverse_dataset_destroyed()", err);
}
/*
* If we didn't make progress, mark the async destroy as
* stalled, so that we will not initiate a spa_sync() on
* its behalf.
*/
scn->scn_async_stalled = (scn->scn_visited_this_txg == 0);
if (bptree_is_empty(dp->dp_meta_objset, dp->dp_bptree_obj)) {
/* finished; deactivate async destroy feature */
spa_feature_decr(spa, SPA_FEATURE_ASYNC_DESTROY, tx);
@ -1478,6 +1471,14 @@ dsl_scan_sync(dsl_pool_t *dp, dmu_tx_t *tx)
dp->dp_bptree_obj, tx));
dp->dp_bptree_obj = 0;
scn->scn_async_destroying = B_FALSE;
} else {
/*
* If we didn't make progress, mark the async destroy as
* stalled, so that we will not initiate a spa_sync() on
* its behalf.
*/
scn->scn_async_stalled =
(scn->scn_visited_this_txg == 0);
}
}
if (scn->scn_visited_this_txg) {