Avoid retrieving unused snapshot props

This patch modifies the zfs_ioc_snapshot_list_next() ioctl to enable it
to take input parameters that alter the way looping through the list of
snapshots is performed. The idea here is to restrict functions that
throw away some of the snapshots returned by the ioctl to a range of
snapshots that these functions actually use. This improves efficiency
and execution speed for some rollback and send operations.

Reviewed-by: Tom Caputi <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Reviewed by: Matt Ahrens <[email protected]>
Signed-off-by: Alek Pinchuk <[email protected]>
Closes #8077 

1 files changed, 60 insertions, 18 deletions

diff --git a/module/zfs/zfs_ioctl.c b/module/zfs/zfs_ioctl.c
index ab40ae185..047193c61 100644
--- a/module/zfs/zfs_ioctl.c
+++ b/module/zfs/zfs_ioctl.c
@@ -34,9 +34,9 @@
  * Copyright 2016 Toomas Soome <[email protected]>
  * Copyright (c) 2016 Actifio, Inc. All rights reserved.
  * Copyright (c) 2018, loli10K <[email protected]>. All rights reserved.
- * Copyright (c) 2017 Datto Inc. All rights reserved.
  * Copyright 2017 RackTop Systems.
  * Copyright (c) 2017 Open-E, Inc. All Rights Reserved.
+ * Copyright (c) 2019 Datto Inc.
  */
 
 /*
@@ -2315,7 +2315,8 @@ top:
  * inputs:
  * zc_name		name of filesystem
  * zc_cookie		zap cursor
- * zc_nvlist_dst_size	size of buffer for property nvlist
+ * zc_nvlist_src	iteration range nvlist
+ * zc_nvlist_src_size	size of iteration range nvlist
  *
  * outputs:
  * zc_name		name of next snapshot
@@ -2326,8 +2327,23 @@ top:
 static int
 zfs_ioc_snapshot_list_next(zfs_cmd_t *zc)
 {
-	objset_t *os;
 	int error;
+	objset_t *os, *ossnap;
+	dsl_dataset_t *ds;
+	uint64_t min_txg = 0, max_txg = 0;
+
+	if (zc->zc_nvlist_src_size != 0) {
+		nvlist_t *props = NULL;
+		error = get_nvlist(zc->zc_nvlist_src, zc->zc_nvlist_src_size,
+		    zc->zc_iflags, &props);
+		if (error != 0)
+			return (error);
+		(void) nvlist_lookup_uint64(props, SNAP_ITER_MIN_TXG,
+		    &min_txg);
+		(void) nvlist_lookup_uint64(props, SNAP_ITER_MAX_TXG,
+		    &max_txg);
+		nvlist_free(props);
+	}
 
 	error = dmu_objset_hold(zc->zc_name, FTAG, &os);
 	if (error != 0) {
@@ -2344,26 +2360,52 @@ zfs_ioc_snapshot_list_next(zfs_cmd_t *zc)
 		return (SET_ERROR(ESRCH));
 	}
 
-	error = dmu_snapshot_list_next(os,
-	    sizeof (zc->zc_name) - strlen(zc->zc_name),
-	    zc->zc_name + strlen(zc->zc_name), &zc->zc_obj, &zc->zc_cookie,
-	    NULL);
+	while (error == 0) {
+		if (issig(JUSTLOOKING) && issig(FORREAL)) {
+			error = SET_ERROR(EINTR);
+			break;
+		}
 
-	if (error == 0 && !zc->zc_simple) {
-		dsl_dataset_t *ds;
-		dsl_pool_t *dp = os->os_dsl_dataset->ds_dir->dd_pool;
+		error = dmu_snapshot_list_next(os,
+		    sizeof (zc->zc_name) - strlen(zc->zc_name),
+		    zc->zc_name + strlen(zc->zc_name), &zc->zc_obj,
+		    &zc->zc_cookie, NULL);
+		if (error == ENOENT) {
+			error = SET_ERROR(ESRCH);
+			break;
+		} else if (error != 0) {
+			break;
+		}
 
-		error = dsl_dataset_hold_obj(dp, zc->zc_obj, FTAG, &ds);
-		if (error == 0) {
-			objset_t *ossnap;
+		error = dsl_dataset_hold_obj(dmu_objset_pool(os), zc->zc_obj,
+		    FTAG, &ds);
+		if (error != 0)
+			break;
 
-			error = dmu_objset_from_ds(ds, &ossnap);
-			if (error == 0)
-				error = zfs_ioc_objset_stats_impl(zc, ossnap);
+		if ((min_txg != 0 && dsl_get_creationtxg(ds) < min_txg) ||
+		    (max_txg != 0 && dsl_get_creationtxg(ds) > max_txg)) {
 			dsl_dataset_rele(ds, FTAG);
+			/* undo snapshot name append */
+			*(strchr(zc->zc_name, '@') + 1) = '\0';
+			/* skip snapshot */
+			continue;
 		}
-	} else if (error == ENOENT) {
-		error = SET_ERROR(ESRCH);
+
+		if (zc->zc_simple) {
+			dsl_dataset_rele(ds, FTAG);
+			break;
+		}
+
+		if ((error = dmu_objset_from_ds(ds, &ossnap)) != 0) {
+			dsl_dataset_rele(ds, FTAG);
+			break;
+		}
+		if ((error = zfs_ioc_objset_stats_impl(zc, ossnap)) != 0) {
+			dsl_dataset_rele(ds, FTAG);
+			break;
+		}
+		dsl_dataset_rele(ds, FTAG);
+		break;
 	}
 
 	dmu_objset_rele(os, FTAG);