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dnode_sync is careless with range tree 

Because dnode_sync_free_range() must drop dn_mtx during its processing,
using it as a callback to range_tree_vacate() is not safe.  No other
operations (besides destroy) are allowed once range_tree_vacate() has
begun, and dropping dn_mtx would leave a window open for another thread
to observe that invalid (and unsafe) state via dnode_block_freed().

Reviewed-by: Matthew Ahrens <mahrens@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Igor Kozhukhov <igor@dilos.org>
Signed-off-by: Patrick Mooney <pmooney@oxide.computer>
Closes #10708 
Closes #10823
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Patrick Mooney 2020-08-26 23:48:29 -05:00 committed by GitHub
parent 600def792e
commit 8d42c98d95
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1 changed files with 12 additions and 2 deletions
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14
module/zfs/dnode_sync.c
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@ -23,6 +23,7 @@
* Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2012, 2018 by Delphix. All rights reserved.
* Copyright (c) 2014 Spectra Logic Corporation, All rights reserved.
* Copyright 2020 Oxide Computer Company
*/
#include <sys/zfs_context.h>
@ -762,13 +763,22 @@ dnode_sync(dnode_t *dn, dmu_tx_t *tx)
dsfra.dsfra_dnode = dn;
dsfra.dsfra_tx = tx;
dsfra.dsfra_free_indirects = freeing_dnode;
mutex_enter(&dn->dn_mtx);
if (freeing_dnode) {
ASSERT(range_tree_contains(dn->dn_free_ranges[txgoff],
0, dn->dn_maxblkid + 1));
}
mutex_enter(&dn->dn_mtx);
range_tree_vacate(dn->dn_free_ranges[txgoff],
/*
* Because dnode_sync_free_range() must drop dn_mtx during its
* processing, using it as a callback to range_tree_vacate() is
* not safe. No other operations (besides destroy) are allowed
* once range_tree_vacate() has begun, and dropping dn_mtx
* would leave a window open for another thread to observe that
* invalid (and unsafe) state.
*/
range_tree_walk(dn->dn_free_ranges[txgoff],
dnode_sync_free_range, &dsfra);
range_tree_vacate(dn->dn_free_ranges[txgoff], NULL, NULL);
range_tree_destroy(dn->dn_free_ranges[txgoff]);
dn->dn_free_ranges[txgoff] = NULL;
mutex_exit(&dn->dn_mtx);