zfs list: Allow more fields in ZFS_ITER_SIMPLE mode

If the fields to be listed and sorted by are constrained to those
populated by dsl_dataset_fast_stat(), then zfs list is much faster,
as it does not need to open each objset and reads its properties.

A previous optimization by Pawel Dawidek
(0cee24064a79f9c01fc4521543c37acea538405f) took advantage
of this to make listing snapshot names sorted only by name much faster.

However, it was limited to `-o name -s name`, this work extends this
optimization to work with:
  - name
  - guid
  - createtxg
  - numclones
  - inconsistent
  - redacted
  - origin
and could be further extended to any other properties supported by
dsl_dataset_fast_stat() or similar, that do not require extra locking
or reading from disk.

This was committed before (9a9e2e343dfa2af28bf7910de77ae73aa006de62),
but was reverted due to a regression when used with an older kernel.

If the kernel does not populate zc->zc_objset_stats, we now fallback
to getting the properties via the slower interface, to avoid problems
with newer userland and older kernels.

Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Allan Jude <[email protected]>
Closes #14110

1 files changed, 2 insertions, 3 deletions

diff --git a/module/zfs/zfs_ioctl.c b/module/zfs/zfs_ioctl.c
index a5168b937..a55d9f88a 100644
--- a/module/zfs/zfs_ioctl.c
+++ b/module/zfs/zfs_ioctl.c
@@ -2039,7 +2039,7 @@ zfs_ioc_objset_stats_impl(zfs_cmd_t *zc, objset_t *os)
 
 	dmu_objset_fast_stat(os, &zc->zc_objset_stats);
 
-	if (zc->zc_nvlist_dst != 0 &&
+	if (!zc->zc_simple && zc->zc_nvlist_dst != 0 &&
 	    (error = dsl_prop_get_all(os, &nv)) == 0) {
 		dmu_objset_stats(os, nv);
 		/*
@@ -2326,8 +2326,7 @@ zfs_ioc_snapshot_list_next(zfs_cmd_t *zc)
 		}
 
 		if (zc->zc_simple) {
-			zc->zc_objset_stats.dds_creation_txg =
-			    dsl_get_creationtxg(ds);
+			dsl_dataset_fast_stat(ds, &zc->zc_objset_stats);
 			dsl_dataset_rele(ds, FTAG);
 			break;
 		}