zfs get: don't lookup mount options when using "-s local"

Looking up mount options can be very expensive on servers with many
mounted file systems.  When doing "zfs get" with any "-s" option that
does not include "temporary", the mount list will never be used.  This
commit optimizes for that case.

This is a breaking commit for libzfs!  Callers of zfs_get_prop are now
required to initialize src.  To preserve existing behavior, they should
initialize it to ZPROP_SRC_NONE.

Sponsored by: Axcient
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Alan Somers <asomers@gmail.com>
Closes #11955

cmd/zfs/zfs_main.c

@@ -1882,7 +1882,6 @@ get_callback(zfs_handle_t *zhp, void *data)
 {
 	char buf[ZFS_MAXPROPLEN];
 	char rbuf[ZFS_MAXPROPLEN];
-	zprop_source_t sourcetype;
 	char source[ZFS_MAX_DATASET_NAME_LEN];
 	zprop_get_cbdata_t *cbp = data;
 	nvlist_t *user_props = zfs_get_user_props(zhp);
@@ -1893,6 +1892,7 @@ get_callback(zfs_handle_t *zhp, void *data)
 	boolean_t received = is_recvd_column(cbp);
 
 	for (; pl != NULL; pl = pl->pl_next) {
+		zprop_source_t sourcetype = cbp->cb_sources;
 		char *recvdval = NULL;
 		/*
 		 * Skip the special fake placeholder.  This will also skip over
@@ -4660,7 +4660,7 @@ zfs_do_send(int argc, char **argv)
 	 */
 	if (fromname && (cp = strchr(fromname, '@')) != NULL) {
 		char origin[ZFS_MAX_DATASET_NAME_LEN];
-		zprop_source_t src;
+		zprop_source_t src = ZPROP_SRC_NONE;
 
 		(void) zfs_prop_get(zhp, ZFS_PROP_ORIGIN,
 		    origin, sizeof (origin), &src, NULL, 0, B_FALSE);

lib/libzfs/libzfs_dataset.c

@@ -2180,7 +2180,8 @@ get_numeric_property(zfs_handle_t *zhp, zfs_prop_t prop, zprop_source_t *src,
 	 * its presence.
 	 */
 	if (!zhp->zfs_mntcheck &&
-	    (mntopt_on != NULL || prop == ZFS_PROP_MOUNTED)) {
+	    (mntopt_on != NULL || prop == ZFS_PROP_MOUNTED) &&
+	    (src && (*src & ZPROP_SRC_TEMPORARY))) {
 		libzfs_handle_t *hdl = zhp->zfs_hdl;
 		struct mnttab entry;
 
@@ -2595,9 +2596,16 @@ zcp_check(zfs_handle_t *zhp, zfs_prop_t prop, uint64_t intval,
 }
 
 /*
- * Retrieve a property from the given object.  If 'literal' is specified, then
+ * Retrieve a property from the given object.
- * numbers are left as exact values.  Otherwise, numbers are converted to a
+ *
- * human-readable form.
+ * Arguments:
+ *  src :	On call, this must contain the bitmap of ZPROP_SRC_* types to
+ * 		query.  Properties whose values come from a different source
+ * 		may not be returned. NULL will be treated as ZPROP_SRC_ALL.  On
+ * 		return, if not NULL, this variable will contain the source for
+ * 		the queried property.
+ *  literal :	If specified, then numbers are left as exact values.  Otherwise,
+ *		they are converted to a human-readable form.
  *
  * Returns 0 on success, or -1 on error.
  */
@@ -2620,9 +2628,6 @@ zfs_prop_get(zfs_handle_t *zhp, zfs_prop_t prop, char *propbuf, size_t proplen,
 	if (received && zfs_prop_readonly(prop))
 		return (-1);
 
-	if (src)
-		*src = ZPROP_SRC_NONE;
-
 	switch (prop) {
 	case ZFS_PROP_CREATION:
 		/*

lib/libzfs/libzfs_diff.c

@@ -575,7 +575,7 @@ get_snapshot_names(differ_info_t *di, const char *fromsnap,
 		 * tosnap is a clone of a fromsnap descendant.
 		 */
 		char origin[ZFS_MAX_DATASET_NAME_LEN];
-		zprop_source_t src;
+		zprop_source_t src = ZPROP_SRC_NONE;
 		zfs_handle_t *zhp;
 
 		di->ds = zfs_alloc(di->zhp->zfs_hdl, tdslen + 1);

lib/libzfs/libzfs_mount.c

@@ -266,7 +266,7 @@ zfs_is_mountable(zfs_handle_t *zhp, char *buf, size_t buflen,
     zprop_source_t *source, int flags)
 {
 	char sourceloc[MAXNAMELEN];
-	zprop_source_t sourcetype;
+	zprop_source_t sourcetype = ZPROP_SRC_NONE;
 
 	if (!zfs_prop_valid_for_type(ZFS_PROP_MOUNTPOINT, zhp->zfs_type,
 	    B_FALSE))
@@ -765,7 +765,7 @@ zfs_share_proto(zfs_handle_t *zhp, zfs_share_proto_t *proto)
 	char shareopts[ZFS_MAXPROPLEN];
 	char sourcestr[ZFS_MAXPROPLEN];
 	zfs_share_proto_t *curr_proto;
-	zprop_source_t sourcetype;
+	zprop_source_t sourcetype = ZPROP_SRC_NONE;
 	int err = 0;
 
 	if (!zfs_is_mountable(zhp, mountpoint, sizeof (mountpoint), NULL, 0))

lib/libzfs/libzfs_sendrecv.c

@@ -2662,7 +2662,7 @@ static zfs_handle_t *
 recv_open_grand_origin(zfs_handle_t *zhp)
 {
 	char origin[ZFS_MAX_DATASET_NAME_LEN];
-	zprop_source_t src;
+	zprop_source_t src = ZPROP_SRC_NONE;
 	zfs_handle_t *ozhp = zfs_handle_dup(zhp);
 
 	while (ozhp != NULL) {