8604 Avoid unnecessary search in VFS when unmounting snapshots

usr/src/uts/common/fs/zfs/dsl_destroy.c

@@ -488,23 +488,29 @@ dsl_destroy_snapshots_nvl(nvlist_t *snaps, boolean_t defer,
 	if (nvlist_next_nvpair(snaps, NULL) == NULL)
 		return (0);
 
-	nvlist_t *arg = fnvlist_alloc();
-	nvlist_t *snaps_normalized = fnvlist_alloc();
 	/*
 	 * lzc_destroy_snaps() is documented to take an nvlist whose
-	 * values "don't matter".  We need to convert that nvlist to one
-	 * that we know can be converted to LUA.
+	 * values "don't matter".  We need to convert that nvlist to
+	 * one that we know can be converted to LUA. We also don't
+	 * care about any duplicate entries because the nvlist will
+	 * be converted to a LUA table which should take care of this.
 	 */
+	nvlist_t *snaps_normalized;
+	VERIFY0(nvlist_alloc(&snaps_normalized, 0, KM_SLEEP));
 	for (nvpair_t *pair = nvlist_next_nvpair(snaps, NULL);
 	    pair != NULL; pair = nvlist_next_nvpair(snaps, pair)) {
 		fnvlist_add_boolean_value(snaps_normalized,
 		    nvpair_name(pair), B_TRUE);
 	}
+
+	nvlist_t *arg;
+	VERIFY0(nvlist_alloc(&arg, 0, KM_SLEEP));
 	fnvlist_add_nvlist(arg, "snaps", snaps_normalized);
 	fnvlist_free(snaps_normalized);
 	fnvlist_add_boolean_value(arg, "defer", defer);
 
-	nvlist_t *wrapper = fnvlist_alloc();
+	nvlist_t *wrapper;
+	VERIFY0(nvlist_alloc(&wrapper, 0, KM_SLEEP));
 	fnvlist_add_nvlist(wrapper, ZCP_ARG_ARGLIST, arg);
 	fnvlist_free(arg);
 
@@ -538,7 +544,7 @@ dsl_destroy_snapshots_nvl(nvlist_t *snaps, boolean_t defer,
 	    program,
 	    0,
 	    zfs_lua_max_memlimit,
-	    fnvlist_lookup_nvpair(wrapper, ZCP_ARG_ARGLIST), result);
+	    nvlist_next_nvpair(wrapper, NULL), result);
 	if (error != 0) {
 		char *errorstr = NULL;
 		(void) nvlist_lookup_string(result, ZCP_RET_ERROR, &errorstr);

usr/src/uts/common/fs/zfs/sys/zfs_ioctl.h

@@ -21,7 +21,7 @@
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2011-2012 Pawel Jakub Dawidek. All rights reserved.
- * Copyright (c) 2012, 2016 by Delphix. All rights reserved.
+ * Copyright (c) 2012, 2017 by Delphix. All rights reserved.
  * Copyright 2016 RackTop Systems.
  * Copyright (c) 2014 Integros [integros.com]
  */
@@ -428,9 +428,10 @@ extern int zfs_secpolicy_snapshot_perms(const char *, cred_t *);
 extern int zfs_secpolicy_rename_perms(const char *, const char *, cred_t *);
 extern int zfs_secpolicy_destroy_perms(const char *, cred_t *);
 extern int zfs_busy(void);
-extern int zfs_unmount_snap(const char *);
+extern void zfs_unmount_snap(const char *);
 extern void zfs_destroy_unmount_origin(const char *);
 extern int getzfsvfs_impl(struct objset *, struct zfsvfs **);
+extern int getzfsvfs(const char *, struct zfsvfs **);
 
 /*
  * ZFS minor numbers can refer to either a control device instance or

usr/src/uts/common/fs/zfs/zfs_ioctl.c

@@ -1417,7 +1417,7 @@ getzfsvfs_impl(objset_t *os, zfsvfs_t **zfvp)
 	return (error);
 }
 
-static int
+int
 getzfsvfs(const char *dsname, zfsvfs_t **zfvp)
 {
 	objset_t *os;
@@ -2988,31 +2988,6 @@ zfs_ioc_get_fsacl(zfs_cmd_t *zc)
 	return (error);
 }
 
-/*
- * Search the vfs list for a specified resource.  Returns a pointer to it
- * or NULL if no suitable entry is found. The caller of this routine
- * is responsible for releasing the returned vfs pointer.
- */
-static vfs_t *
-zfs_get_vfs(const char *resource)
-{
-	struct vfs *vfsp;
-	struct vfs *vfs_found = NULL;
-
-	vfs_list_read_lock();
-	vfsp = rootvfs;
-	do {
-		if (strcmp(refstr_value(vfsp->vfs_resource), resource) == 0) {
-			VFS_HOLD(vfsp);
-			vfs_found = vfsp;
-			break;
-		}
-		vfsp = vfsp->vfs_next;
-	} while (vfsp != rootvfs);
-	vfs_list_unlock();
-	return (vfs_found);
-}
-
 /* ARGSUSED */
 static void
 zfs_create_cb(objset_t *os, void *arg, cred_t *cr, dmu_tx_t *tx)
@@ -3439,40 +3414,41 @@ zfs_ioc_log_history(const char *unused, nvlist_t *innvl, nvlist_t *outnvl)
  * Returns 0 if the argument is not a snapshot, or it is not currently a
  * filesystem, or we were able to unmount it.  Returns error code otherwise.
  */
-int
+void
 zfs_unmount_snap(const char *snapname)
 {
-	vfs_t *vfsp;
-	zfsvfs_t *zfsvfs;
-	int err;
+	vfs_t *vfsp = NULL;
+	zfsvfs_t *zfsvfs = NULL;
 
 	if (strchr(snapname, '@') == NULL)
-		return (0);
+		return;
 
-	vfsp = zfs_get_vfs(snapname);
-	if (vfsp == NULL)
-		return (0);
+	int err = getzfsvfs(snapname, &zfsvfs);
+	if (err != 0) {
+		ASSERT3P(zfsvfs, ==, NULL);
+		return;
+	}
+	vfsp = zfsvfs->z_vfs;
 
-	zfsvfs = vfsp->vfs_data;
 	ASSERT(!dsl_pool_config_held(dmu_objset_pool(zfsvfs->z_os)));
 
 	err = vn_vfswlock(vfsp->vfs_vnodecovered);
 	VFS_RELE(vfsp);
 	if (err != 0)
-		return (SET_ERROR(err));
+		return;
 
 	/*
 	 * Always force the unmount for snapshots.
 	 */
 	(void) dounmount(vfsp, MS_FORCE, kcred);
-	return (0);
 }
 
 /* ARGSUSED */
 static int
 zfs_unmount_snap_cb(const char *snapname, void *arg)
 {
-	return (zfs_unmount_snap(snapname));
+	zfs_unmount_snap(snapname);
+	return (0);
 }
 
 /*
@@ -3495,7 +3471,7 @@ zfs_destroy_unmount_origin(const char *fsname)
 		char originname[ZFS_MAX_DATASET_NAME_LEN];
 		dsl_dataset_name(ds->ds_prev, originname);
 		dmu_objset_rele(os, FTAG);
-		(void) zfs_unmount_snap(originname);
+		zfs_unmount_snap(originname);
 	} else {
 		dmu_objset_rele(os, FTAG);
 	}
@@ -3524,7 +3500,7 @@ zfs_ioc_destroy_snaps(const char *poolname, nvlist_t *innvl, nvlist_t *outnvl)
 
 	for (pair = nvlist_next_nvpair(snaps, NULL); pair != NULL;
 	    pair = nvlist_next_nvpair(snaps, pair)) {
-		(void) zfs_unmount_snap(nvpair_name(pair));
+		zfs_unmount_snap(nvpair_name(pair));
 	}
 
 	return (dsl_destroy_snapshots_nvl(snaps, defer, outnvl));
@@ -3667,11 +3643,8 @@ zfs_ioc_destroy(zfs_cmd_t *zc)
 {
 	int err;
 
-	if (zc->zc_objset_type == DMU_OST_ZFS) {
-		err = zfs_unmount_snap(zc->zc_name);
-		if (err != 0)
-			return (err);
-	}
+	if (zc->zc_objset_type == DMU_OST_ZFS)
+		zfs_unmount_snap(zc->zc_name);
 
 	if (strchr(zc->zc_name, '@'))
 		err = dsl_destroy_snapshot(zc->zc_name, zc->zc_defer_destroy);
@@ -3735,7 +3708,9 @@ recursive_unmount(const char *fsname, void *arg)
 	char fullname[ZFS_MAX_DATASET_NAME_LEN];
 
 	(void) snprintf(fullname, sizeof (fullname), "%s@%s", fsname, snapname);
-	return (zfs_unmount_snap(fullname));
+	zfs_unmount_snap(fullname);
+
+	return (0);
 }
 
 /*