Author: avg
Date: Thu Mar 23 07:57:42 2017
New Revision: 315833
URL: https://svnweb.freebsd.org/changeset/base/315833
Log:
MFC r314912: MFV r314910: 7843 get_clones_stat() is suboptimal for lots of
clones
Modified:
stable/10/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_dataset.c
Directory Properties:
stable/10/ (props changed)
Modified: stable/10/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_dataset.c
==============================================================================
--- stable/10/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_dataset.c
Thu Mar 23 07:57:37 2017 (r315832)
+++ stable/10/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_dataset.c
Thu Mar 23 07:57:42 2017 (r315833)
@@ -1766,11 +1766,22 @@ get_clones_stat(dsl_dataset_t *ds, nvlis
zap_cursor_t zc;
zap_attribute_t za;
nvlist_t *propval = fnvlist_alloc();
- nvlist_t *val = fnvlist_alloc();
+ nvlist_t *val;
ASSERT(dsl_pool_config_held(ds->ds_dir->dd_pool));
/*
+ * We use nvlist_alloc() instead of fnvlist_alloc() because the
+ * latter would allocate the list with NV_UNIQUE_NAME flag.
+ * As a result, every time a clone name is appended to the list
+ * it would be (linearly) searched for for a duplicate name.
+ * We already know that all clone names must be unique and we
+ * want avoid the quadratic complexity of double-checking that
+ * because we can have a large number of clones.
+ */
+ VERIFY0(nvlist_alloc(&val, 0, KM_SLEEP));
+
+ /*
* There may be missing entries in ds_next_clones_obj
* due to a bug in a previous version of the code.
* Only trust it if it has the right number of entries.
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