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-rw-r--r--module/zfs/dsl_dataset.c13
1 files changed, 12 insertions, 1 deletions
diff --git a/module/zfs/dsl_dataset.c b/module/zfs/dsl_dataset.c
index 6c9bcbc9f..c91c2e991 100644
--- a/module/zfs/dsl_dataset.c
+++ b/module/zfs/dsl_dataset.c
@@ -1753,11 +1753,22 @@ get_clones_stat(dsl_dataset_t *ds, nvlist_t *nv)
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.