Use dsl_dataset_snap_lookup()

Retire the dmu_snapshot_id() function which was introduced in the
initial .zfs control directory implementation.  There is already
an existing dsl_dataset_snap_lookup() which does exactly what we
need, and the dmu_snapshot_id() function as implemented is racy.

https://github.com/zfsonlinux/zfs/issues/1215#issuecomment-12579879

Signed-off-by: Brian Behlendorf <[email protected]>
Closes #1238

1 files changed, 2 insertions, 31 deletions

diff --git a/module/zfs/dmu_objset.c b/module/zfs/dmu_objset.c
index 628b23be1..c59973a77 100644
--- a/module/zfs/dmu_objset.c
+++ b/module/zfs/dmu_objset.c
@@ -1573,39 +1573,10 @@ dmu_snapshot_list_next(objset_t *os, int namelen, char *name,
 	return (0);
 }
 
-/*
- * Determine the objset id for a given snapshot name.
- */
 int
-dmu_snapshot_id(objset_t *os, const char *snapname, uint64_t *idp)
+dmu_snapshot_lookup(objset_t *os, const char *name, uint64_t *value)
 {
-	dsl_dataset_t *ds = os->os_dsl_dataset;
-	zap_cursor_t cursor;
-	zap_attribute_t attr;
-	int error;
-
-	if (ds->ds_phys->ds_snapnames_zapobj == 0)
-		return (ENOENT);
-
-	zap_cursor_init(&cursor, ds->ds_dir->dd_pool->dp_meta_objset,
-	    ds->ds_phys->ds_snapnames_zapobj);
-
-	error = zap_cursor_move_to_key(&cursor, snapname, MT_EXACT);
-	if (error) {
-		zap_cursor_fini(&cursor);
-		return (error);
-	}
-
-	error = zap_cursor_retrieve(&cursor, &attr);
-	if (error) {
-		zap_cursor_fini(&cursor);
-		return (error);
-	}
-
-	*idp = attr.za_first_integer;
-	zap_cursor_fini(&cursor);
-
-	return (0);
+	return dsl_dataset_snap_lookup(os->os_dsl_dataset, name, value);
 }
 
 int