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Don't dirty bpobj if it has no entries 

In certain cases (dsl_scan_sync() is one), we may end up calling
bpobj_iterate() on an empty bpobj. Even though we don't end up
modifying the bpobj it still gets dirtied, causing unneeded writes
to the pool.

This patch adds an early bail from bpobj_iterate_impl() if bpobj
is empty to prevent unneeded writes.

Reviewed-by: George Melikov <mail@gmelikov.ru>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Signed-off-by: Alek Pinchuk <apinchuk@datto.com>
Closes #6164
This commit is contained in:
Alek P 2017-05-26 08:42:10 -10:00 committed by Brian Behlendorf
parent 261c013fbf
commit 9210e43a16
1 changed files with 4 additions and 0 deletions
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4
module/zfs/bpobj.c
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@ -21,6 +21,7 @@
/*
* Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2011, 2016 by Delphix. All rights reserved.
* Copyright (c) 2017 Datto Inc.
*/
#include <sys/bpobj.h>
@ -211,6 +212,9 @@ bpobj_iterate_impl(bpobj_t *bpo, bpobj_itor_t func, void *arg, dmu_tx_t *tx,
mutex_enter(&bpo->bpo_lock);
if (!bpobj_hasentries(bpo))
goto out;
if (free)
dmu_buf_will_dirty(bpo->bpo_dbuf, tx);