Add 'zfs send --saved' flag

This commit adds the --saved (-S) to the 'zfs send' command.
This flag allows a user to send a partially received dataset,
which can be useful when migrating a backup server to new
hardware. This flag is compatible with resumable receives, so
even if the saved send is interrupted, it can be resumed.
The flag does not require any user / kernel ABI changes or any
new feature flags in the send stream format.

Reviewed-by: Paul Dagnelie <[email protected]>
Reviewed-by: Alek Pinchuk <[email protected]>
Reviewed-by: Paul Zuchowski <[email protected]>
Reviewed-by: Christian Schwarz <[email protected]>
Reviewed-by: Matt Ahrens <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Tom Caputi <[email protected]>
Closes #9007 

1 files changed, 142 insertions, 31 deletions

diff --git a/module/zfs/dmu_send.c b/module/zfs/dmu_send.c
index b0a56650e..62de978d3 100644
--- a/module/zfs/dmu_send.c
+++ b/module/zfs/dmu_send.c
@@ -51,6 +51,7 @@
 #include <sys/ddt.h>
 #include <sys/zfs_onexit.h>
 #include <sys/dmu_send.h>
+#include <sys/dmu_recv.h>
 #include <sys/dsl_destroy.h>
 #include <sys/blkptr.h>
 #include <sys/dsl_bookmark.h>
@@ -1888,8 +1889,11 @@ struct dmu_send_params {
 	boolean_t embedok;
 	boolean_t large_block_ok;
 	boolean_t compressok;
+	boolean_t rawok;
+	boolean_t savedok;
 	uint64_t resumeobj;
 	uint64_t resumeoff;
+	uint64_t saved_guid;
 	zfs_bookmark_phys_t *redactbook;
 	/* Stream output params */
 	dmu_send_outparams_t *dso;
@@ -1897,7 +1901,7 @@ struct dmu_send_params {
 	/* Stream progress params */
 	offset_t *off;
 	int outfd;
-	boolean_t rawok;
+	char saved_toname[MAXNAMELEN];
 };
 
 static int
@@ -1984,10 +1988,15 @@ create_begin_record(struct dmu_send_params *dspp, objset_t *os,
 		drrb->drr_flags |= DRR_FLAG_FREERECORDS;
 	drr->drr_u.drr_begin.drr_flags |= DRR_FLAG_SPILL_BLOCK;
 
-	dsl_dataset_name(to_ds, drrb->drr_toname);
-	if (!to_ds->ds_is_snapshot) {
-		(void) strlcat(drrb->drr_toname, "@--head--",
-		    sizeof (drrb->drr_toname));
+	if (dspp->savedok) {
+		drrb->drr_toguid = dspp->saved_guid;
+		strcpy(drrb->drr_toname, dspp->saved_toname);
+	} else {
+		dsl_dataset_name(to_ds, drrb->drr_toname);
+		if (!to_ds->ds_is_snapshot) {
+			(void) strlcat(drrb->drr_toname, "@--head--",
+			    sizeof (drrb->drr_toname));
+		}
 	}
 	return (drr);
 }
@@ -2305,6 +2314,7 @@ dmu_send_impl(struct dmu_send_params *dspp)
 		dsl_pool_rele(dp, tag);
 		return (err);
 	}
+
 	/*
 	 * If this is a non-raw send of an encrypted ds, we can ensure that
 	 * the objset_phys_t is authenticated. This is safe because this is
@@ -2526,19 +2536,27 @@ dmu_send_impl(struct dmu_send_params *dspp)
 		goto out;
 	}
 
-	bzero(drr, sizeof (dmu_replay_record_t));
-	drr->drr_type = DRR_END;
-	drr->drr_u.drr_end.drr_checksum = dsc.dsc_zc;
-	drr->drr_u.drr_end.drr_toguid = dsc.dsc_toguid;
+	/*
+	 * Send the DRR_END record if this is not a saved stream.
+	 * Otherwise, the omitted DRR_END record will signal to
+	 * the receive side that the stream is incomplete.
+	 */
+	if (!dspp->savedok) {
+		bzero(drr, sizeof (dmu_replay_record_t));
+		drr->drr_type = DRR_END;
+		drr->drr_u.drr_end.drr_checksum = dsc.dsc_zc;
+		drr->drr_u.drr_end.drr_toguid = dsc.dsc_toguid;
 
-	if (dump_record(&dsc, NULL, 0) != 0)
-		err = dsc.dsc_err;
+		if (dump_record(&dsc, NULL, 0) != 0)
+			err = dsc.dsc_err;
+	}
 out:
 	mutex_enter(&to_ds->ds_sendstream_lock);
 	list_remove(&to_ds->ds_sendstreams, dssp);
 	mutex_exit(&to_ds->ds_sendstream_lock);
 
-	VERIFY(err != 0 || (dsc.dsc_sent_begin && dsc.dsc_sent_end));
+	VERIFY(err != 0 || (dsc.dsc_sent_begin &&
+	    (dsc.dsc_sent_end || dspp->savedok)));
 
 	kmem_free(drr, sizeof (dmu_replay_record_t));
 	kmem_free(dssp, sizeof (dmu_sendstatus_t));
@@ -2564,7 +2582,8 @@ out:
 int
 dmu_send_obj(const char *pool, uint64_t tosnap, uint64_t fromsnap,
     boolean_t embedok, boolean_t large_block_ok, boolean_t compressok,
-    boolean_t rawok, int outfd, offset_t *off, dmu_send_outparams_t *dsop)
+    boolean_t rawok, boolean_t savedok, int outfd, offset_t *off,
+    dmu_send_outparams_t *dsop)
 {
 	int err;
 	dsl_dataset_t *fromds;
@@ -2578,6 +2597,7 @@ dmu_send_obj(const char *pool, uint64_t tosnap, uint64_t fromsnap,
 	dspp.dso = dsop;
 	dspp.tag = FTAG;
 	dspp.rawok = rawok;
+	dspp.savedok = savedok;
 
 	err = dsl_pool_hold(pool, FTAG, &dspp.dp);
 	if (err != 0)
@@ -2644,8 +2664,9 @@ dmu_send_obj(const char *pool, uint64_t tosnap, uint64_t fromsnap,
 int
 dmu_send(const char *tosnap, const char *fromsnap, boolean_t embedok,
     boolean_t large_block_ok, boolean_t compressok, boolean_t rawok,
-    uint64_t resumeobj, uint64_t resumeoff, const char *redactbook, int outfd,
-    offset_t *off, dmu_send_outparams_t *dsop)
+    boolean_t savedok, uint64_t resumeobj, uint64_t resumeoff,
+    const char *redactbook, int outfd, offset_t *off,
+    dmu_send_outparams_t *dsop)
 {
 	int err = 0;
 	ds_hold_flags_t dsflags = (rawok) ? 0 : DS_HOLD_FLAG_DECRYPT;
@@ -2653,6 +2674,7 @@ dmu_send(const char *tosnap, const char *fromsnap, boolean_t embedok,
 	dsl_dataset_t *fromds = NULL;
 	zfs_bookmark_phys_t book = {0};
 	struct dmu_send_params dspp = {0};
+
 	dspp.tosnap = tosnap;
 	dspp.embedok = embedok;
 	dspp.large_block_ok = large_block_ok;
@@ -2664,6 +2686,7 @@ dmu_send(const char *tosnap, const char *fromsnap, boolean_t embedok,
 	dspp.resumeobj = resumeobj;
 	dspp.resumeoff = resumeoff;
 	dspp.rawok = rawok;
+	dspp.savedok = savedok;
 
 	if (fromsnap != NULL && strpbrk(fromsnap, "@#") == NULL)
 		return (SET_ERROR(EINVAL));
@@ -2671,13 +2694,57 @@ dmu_send(const char *tosnap, const char *fromsnap, boolean_t embedok,
 	err = dsl_pool_hold(tosnap, FTAG, &dspp.dp);
 	if (err != 0)
 		return (err);
+
 	if (strchr(tosnap, '@') == NULL && spa_writeable(dspp.dp->dp_spa)) {
 		/*
 		 * We are sending a filesystem or volume.  Ensure
 		 * that it doesn't change by owning the dataset.
 		 */
-		err = dsl_dataset_own(dspp.dp, tosnap, dsflags, FTAG,
-		    &dspp.to_ds);
+
+		if (savedok) {
+			/*
+			 * We are looking for the dataset that represents the
+			 * partially received send stream. If this stream was
+			 * received as a new snapshot of an existing dataset,
+			 * this will be saved in a hidden clone named
+			 * "<pool>/<dataset>/%recv". Otherwise, the stream
+			 * will be saved in the live dataset itself. In
+			 * either case we need to use dsl_dataset_own_force()
+			 * because the stream is marked as inconsistent,
+			 * which would normally make it unavailable to be
+			 * owned.
+			 */
+			char *name = kmem_asprintf("%s/%s", tosnap,
+			    recv_clone_name);
+			err = dsl_dataset_own_force(dspp.dp, name, dsflags,
+			    FTAG, &dspp.to_ds);
+			if (err == ENOENT) {
+				err = dsl_dataset_own_force(dspp.dp, tosnap,
+				    dsflags, FTAG, &dspp.to_ds);
+			}
+
+			if (err == 0) {
+				err = zap_lookup(dspp.dp->dp_meta_objset,
+				    dspp.to_ds->ds_object,
+				    DS_FIELD_RESUME_TOGUID, 8, 1,
+				    &dspp.saved_guid);
+			}
+
+			if (err == 0) {
+				err = zap_lookup(dspp.dp->dp_meta_objset,
+				    dspp.to_ds->ds_object,
+				    DS_FIELD_RESUME_TONAME, 1,
+				    sizeof (dspp.saved_toname),
+				    dspp.saved_toname);
+			}
+			if (err != 0)
+				dsl_dataset_disown(dspp.to_ds, dsflags, FTAG);
+
+			kmem_strfree(name);
+		} else {
+			err = dsl_dataset_own(dspp.dp, tosnap, dsflags,
+			    FTAG, &dspp.to_ds);
+		}
 		owned = B_TRUE;
 	} else {
 		err = dsl_dataset_hold_flags(dspp.dp, tosnap, dsflags, FTAG,
@@ -2763,9 +2830,6 @@ dmu_send(const char *tosnap, const char *fromsnap, boolean_t embedok,
 				    0)) {
 					err = SET_ERROR(EXDEV);
 				} else {
-					ASSERT3U(dspp.is_clone, ==,
-					    (dspp.to_ds->ds_dir !=
-					    fromds->ds_dir));
 					zb->zbm_creation_txg =
 					    dsl_dataset_phys(fromds)->
 					    ds_creation_txg;
@@ -2870,37 +2934,80 @@ dmu_adjust_send_estimate_for_indirects(dsl_dataset_t *ds, uint64_t uncompressed,
 }
 
 int
-dmu_send_estimate_fast(dsl_dataset_t *ds, dsl_dataset_t *fromds,
-    zfs_bookmark_phys_t *frombook, boolean_t stream_compressed, uint64_t *sizep)
+dmu_send_estimate_fast(dsl_dataset_t *origds, dsl_dataset_t *fromds,
+    zfs_bookmark_phys_t *frombook, boolean_t stream_compressed,
+    boolean_t saved, uint64_t *sizep)
 {
 	int err;
+	dsl_dataset_t *ds = origds;
 	uint64_t uncomp, comp;
 
-	ASSERT(dsl_pool_config_held(ds->ds_dir->dd_pool));
+	ASSERT(dsl_pool_config_held(origds->ds_dir->dd_pool));
 	ASSERT(fromds == NULL || frombook == NULL);
 
-	/* tosnap must be a snapshot */
-	if (!ds->ds_is_snapshot)
+	/*
+	 * If this is a saved send we may actually be sending
+	 * from the %recv clone used for resuming.
+	 */
+	if (saved) {
+		objset_t *mos = origds->ds_dir->dd_pool->dp_meta_objset;
+		uint64_t guid;
+		char dsname[ZFS_MAX_DATASET_NAME_LEN + 6];
+
+		dsl_dataset_name(origds, dsname);
+		(void) strcat(dsname, "/");
+		(void) strcat(dsname, recv_clone_name);
+
+		err = dsl_dataset_hold(origds->ds_dir->dd_pool,
+		    dsname, FTAG, &ds);
+		if (err != ENOENT && err != 0) {
+			return (err);
+		} else if (err == ENOENT) {
+			ds = origds;
+		}
+
+		/* check that this dataset has partially received data */
+		err = zap_lookup(mos, ds->ds_object,
+		    DS_FIELD_RESUME_TOGUID, 8, 1, &guid);
+		if (err != 0) {
+			err = SET_ERROR(err == ENOENT ? EINVAL : err);
+			goto out;
+		}
+
+		err = zap_lookup(mos, ds->ds_object,
+		    DS_FIELD_RESUME_TONAME, 1, sizeof (dsname), dsname);
+		if (err != 0) {
+			err = SET_ERROR(err == ENOENT ? EINVAL : err);
+			goto out;
+		}
+	}
+
+	/* tosnap must be a snapshot or the target of a saved send */
+	if (!ds->ds_is_snapshot && ds == origds)
 		return (SET_ERROR(EINVAL));
 
 	if (fromds != NULL) {
 		uint64_t used;
-		if (!fromds->ds_is_snapshot)
-			return (SET_ERROR(EINVAL));
+		if (!fromds->ds_is_snapshot) {
+			err = SET_ERROR(EINVAL);
+			goto out;
+		}
 
-		if (!dsl_dataset_is_before(ds, fromds, 0))
-			return (SET_ERROR(EXDEV));
+		if (!dsl_dataset_is_before(ds, fromds, 0)) {
+			err = SET_ERROR(EXDEV);
+			goto out;
+		}
 
 		err = dsl_dataset_space_written(fromds, ds, &used, &comp,
 		    &uncomp);
 		if (err != 0)
-			return (err);
+			goto out;
 	} else if (frombook != NULL) {
 		uint64_t used;
 		err = dsl_dataset_space_written_bookmark(frombook, ds, &used,
 		    &comp, &uncomp);
 		if (err != 0)
-			return (err);
+			goto out;
 	} else {
 		uncomp = dsl_dataset_phys(ds)->ds_uncompressed_bytes;
 		comp = dsl_dataset_phys(ds)->ds_compressed_bytes;
@@ -2912,6 +3019,10 @@ dmu_send_estimate_fast(dsl_dataset_t *ds, dsl_dataset_t *fromds,
 	 * Add the size of the BEGIN and END records to the estimate.
 	 */
 	*sizep += 2 * sizeof (dmu_replay_record_t);
+
+out:
+	if (ds != origds)
+		dsl_dataset_rele(ds, FTAG);
 	return (err);
 }