Illumos #3894

3894 zfs should not allow snapshot of inconsistent dataset
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Approved by: Gordon Ross <gwr@nexenta.com>

References:
  https://www.illumos.org/issues/3894
  illumos/illumos-gate@ca48f36f20

Ported-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #1775

cmd/zfs/zfs_main.c

@@ -3480,6 +3480,12 @@ zfs_snapshot_cb(zfs_handle_t *zhp, void *arg)
 	int rv = 0;
 	int error;
 
+	if (sd->sd_recursive &&
+	    zfs_prop_get_int(zhp, ZFS_PROP_INCONSISTENT) != 0) {
+		zfs_close(zhp);
+		return (0);
+	}
+
 	error = asprintf(&name, "%s@%s", zfs_get_name(zhp), sd->sd_snapname);
 	if (error == -1)
 		nomem();

include/sys/dsl_dataset.h

@@ -251,7 +251,7 @@ int dsl_dataset_clone_swap_check_impl(dsl_dataset_t *clone,
 void dsl_dataset_clone_swap_sync_impl(dsl_dataset_t *clone,
     dsl_dataset_t *origin_head, dmu_tx_t *tx);
 int dsl_dataset_snapshot_check_impl(dsl_dataset_t *ds, const char *snapname,
-    dmu_tx_t *tx);
+    dmu_tx_t *tx, boolean_t recv);
 void dsl_dataset_snapshot_sync_impl(dsl_dataset_t *ds, const char *snapname,
     dmu_tx_t *tx);
 

include/sys/fs/zfs.h

@@ -140,6 +140,7 @@ typedef enum {
 	ZFS_PROP_CLONES,
 	ZFS_PROP_LOGICALUSED,
 	ZFS_PROP_LOGICALREFERENCED,
+	ZFS_PROP_INCONSISTENT,		/* not exposed to the user */
 	ZFS_PROP_SNAPDEV,
 	ZFS_PROP_ACLTYPE,
 	ZFS_NUM_PROPS

lib/libzfs/libzfs_dataset.c

@@ -1872,6 +1872,10 @@ get_numeric_property(zfs_handle_t *zhp, zfs_prop_t prop, zprop_source_t *src,
 		zcmd_free_nvlists(&zc);
 		break;
 
+	case ZFS_PROP_INCONSISTENT:
+		*val = zhp->zfs_dmustats.dds_inconsistent;
+		break;
+
 	default:
 		switch (zfs_prop_get_type(prop)) {
 		case PROP_TYPE_NUMBER:
@@ -3514,13 +3518,16 @@ zfs_snapshot_cb(zfs_handle_t *zhp, void *arg)
 	char name[ZFS_MAXNAMELEN];
 	int rv = 0;
 
-	(void) snprintf(name, sizeof (name),
+	if (zfs_prop_get_int(zhp, ZFS_PROP_INCONSISTENT) == 0) {
-	    "%s@%s", zfs_get_name(zhp), sd->sd_snapname);
+		(void) snprintf(name, sizeof (name),
+		    "%s@%s", zfs_get_name(zhp), sd->sd_snapname);
 
-	fnvlist_add_boolean(sd->sd_nvl, name);
+		fnvlist_add_boolean(sd->sd_nvl, name);
 
-	rv = zfs_iter_filesystems(zhp, zfs_snapshot_cb, sd);
+		rv = zfs_iter_filesystems(zhp, zfs_snapshot_cb, sd);
+	}
 	zfs_close(zhp);
+
 	return (rv);
 }
 

module/zcommon/zfs_prop.c

@@ -410,6 +410,8 @@ zfs_prop_init(void)
 	    PROP_READONLY, ZFS_TYPE_DATASET, "UNIQUE");
 	zprop_register_hidden(ZFS_PROP_OBJSETID, "objsetid", PROP_TYPE_NUMBER,
 	    PROP_READONLY, ZFS_TYPE_DATASET, "OBJSETID");
+	zprop_register_hidden(ZFS_PROP_INCONSISTENT, "inconsistent",
+	    PROP_TYPE_NUMBER, PROP_READONLY, ZFS_TYPE_DATASET, "INCONSISTENT");
 
 	/*
 	 * Property to be removed once libbe is integrated

module/zfs/dmu_send.c

@@ -1584,7 +1584,7 @@ dmu_recv_end_check(void *arg, dmu_tx_t *tx)
 			return (error);
 		}
 		error = dsl_dataset_snapshot_check_impl(origin_head,
-		    drc->drc_tosnap, tx);
+		    drc->drc_tosnap, tx, B_TRUE);
 		dsl_dataset_rele(origin_head, FTAG);
 		if (error != 0)
 			return (error);
@@ -1592,7 +1592,7 @@ dmu_recv_end_check(void *arg, dmu_tx_t *tx)
 		error = dsl_destroy_head_check_impl(drc->drc_ds, 1);
 	} else {
 		error = dsl_dataset_snapshot_check_impl(drc->drc_ds,
-		    drc->drc_tosnap, tx);
+		    drc->drc_tosnap, tx, B_TRUE);
 	}
 	return (error);
 }

module/zfs/dsl_dataset.c

@@ -929,7 +929,7 @@ typedef struct dsl_dataset_snapshot_arg {
 
 int
 dsl_dataset_snapshot_check_impl(dsl_dataset_t *ds, const char *snapname,
-    dmu_tx_t *tx)
+    dmu_tx_t *tx, boolean_t recv)
 {
 	int error;
 	uint64_t value;
@@ -955,6 +955,18 @@ dsl_dataset_snapshot_check_impl(dsl_dataset_t *ds, const char *snapname,
 	if (error != ENOENT)
 		return (error);
 
+	/*
+	 * We don't allow taking snapshots of inconsistent datasets, such as
+	 * those into which we are currently receiving.  However, if we are
+	 * creating this snapshot as part of a receive, this check will be
+	 * executed atomically with respect to the completion of the receive
+	 * itself but prior to the clearing of DS_FLAG_INCONSISTENT; in this
+	 * case we ignore this, knowing it will be fixed up for us shortly in
+	 * dmu_recv_end_sync().
+	 */
+	if (!recv && DS_IS_INCONSISTENT(ds))
+		return (SET_ERROR(EBUSY));
+
 	error = dsl_dataset_snapshot_reserve_space(ds, tx);
 	if (error != 0)
 		return (error);
@@ -991,7 +1003,7 @@ dsl_dataset_snapshot_check(void *arg, dmu_tx_t *tx)
 			error = dsl_dataset_hold(dp, dsname, FTAG, &ds);
 		if (error == 0) {
 			error = dsl_dataset_snapshot_check_impl(ds,
-			    atp + 1, tx);
+			    atp + 1, tx, B_FALSE);
 			dsl_dataset_rele(ds, FTAG);
 		}
 
@@ -1243,7 +1255,8 @@ dsl_dataset_snapshot_tmp_check(void *arg, dmu_tx_t *tx)
 	if (error != 0)
 		return (error);
 
-	error = dsl_dataset_snapshot_check_impl(ds, ddsta->ddsta_snapname, tx);
+	error = dsl_dataset_snapshot_check_impl(ds, ddsta->ddsta_snapname,
+	    tx, B_FALSE);
 	if (error != 0) {
 		dsl_dataset_rele(ds, FTAG);
 		return (error);