diff options
| author | Brian Behlendorf <[email protected]> | 2017-03-07 09:47:40 -0800 |
|---|---|---|
| committer | GitHub <[email protected]> | 2017-03-07 09:47:40 -0800 |
| commit | e2fcb562759f32d3ca6f3764914222132ce2cfd9 (patch) | |
| tree | b2b50b7a7cbee4ea1f929b96147737dea3029d47 | |
| parent | 3c9e0d673e1d47622e6be0bdb06d53fa8655cdf3 (diff) | |
OpenZFS 7843 - get_clones_stat() is suboptimal for lots of clones
Reviewed by: Pavel Zakharov <[email protected]>
Reviewed by: Matthew Ahrens <[email protected]>
Reviewed-by: George Melikov <[email protected]>
Reviewed-by: Giuseppe Di Natale <[email protected]>
Ported-by: Brian Behlendorf <[email protected]>
OpenZFS-issue: https://www.illumos.org/issues/7843
OpenZFS-commit: https://github.com/openzfs/openzfs/commit/4d519e7
Closes #5868
| -rw-r--r-- | module/zfs/dsl_dataset.c | 13 |
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. |