Raw sends must be able to decrease nlevels

Currently, when a raw zfs send file includes a DRR_OBJECT record
that would decrease the number of levels of an existing object,
the object is reallocated with dmu_object_reclaim() which
creates the new dnode using the old object's nlevels. For non-raw
sends this doesn't really matter, but raw sends require that
nlevels on the receive side match that of the send side so that
the checksum-of-MAC tree can be properly maintained. This patch
corrects the issue by freeing the object completely before
allocating it again in this case.

This patch also corrects several issues with dnode_hold_impl()
and related functions that prevented dnodes (particularly
multi-slot dnodes) from being reallocated properly due to
the fact that existing dnodes were not being fully cleaned up
when they were freed.

This patch adds a test to make sure that zfs recv functions
properly with incremental streams containing dnodes of different
sizes.

Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed-by: Jorgen Lundman <lundman@lundman.net>
Signed-off-by: Tom Caputi <tcaputi@datto.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #6821
Closes #6864

cmd/ztest/ztest.c

@@ -201,6 +201,7 @@ extern unsigned long zfs_deadman_synctime_ms;
 extern int metaslab_preload_limit;
 extern boolean_t zfs_compressed_arc_enabled;
 extern int zfs_abd_scatter_enabled;
+extern int dmu_object_alloc_chunk_shift;
 
 static ztest_shared_opts_t *ztest_shared_opts;
 static ztest_shared_opts_t ztest_opts;
@@ -314,6 +315,7 @@ static ztest_shared_callstate_t *ztest_shared_callstate;
 ztest_func_t ztest_dmu_read_write;
 ztest_func_t ztest_dmu_write_parallel;
 ztest_func_t ztest_dmu_object_alloc_free;
+ztest_func_t ztest_dmu_object_next_chunk;
 ztest_func_t ztest_dmu_commit_callbacks;
 ztest_func_t ztest_zap;
 ztest_func_t ztest_zap_parallel;
@@ -361,6 +363,7 @@ ztest_info_t ztest_info[] = {
 	ZTI_INIT(ztest_dmu_read_write, 1, &zopt_always),
 	ZTI_INIT(ztest_dmu_write_parallel, 10, &zopt_always),
 	ZTI_INIT(ztest_dmu_object_alloc_free, 1, &zopt_always),
+	ZTI_INIT(ztest_dmu_object_next_chunk, 1, &zopt_sometimes),
 	ZTI_INIT(ztest_dmu_commit_callbacks, 1, &zopt_always),
 	ZTI_INIT(ztest_zap, 30, &zopt_always),
 	ZTI_INIT(ztest_zap_parallel, 100, &zopt_always),
@@ -4055,6 +4058,26 @@ ztest_dmu_object_alloc_free(ztest_ds_t *zd, uint64_t id)
 	umem_free(od, size);
 }
 
+/*
+ * Rewind the global allocator to verify object allocation backfilling.
+ */
+void
+ztest_dmu_object_next_chunk(ztest_ds_t *zd, uint64_t id)
+{
+	objset_t *os = zd->zd_os;
+	int dnodes_per_chunk = 1 << dmu_object_alloc_chunk_shift;
+	uint64_t object;
+
+	/*
+	 * Rewind the global allocator randomly back to a lower object number
+	 * to force backfilling and reclamation of recently freed dnodes.
+	 */
+	mutex_enter(&os->os_obj_lock);
+	object = ztest_random(os->os_obj_next_chunk);
+	os->os_obj_next_chunk = P2ALIGN(object, dnodes_per_chunk);
+	mutex_exit(&os->os_obj_lock);
+}
+
 #undef OD_ARRAY_SIZE
 #define	OD_ARRAY_SIZE	2
 

include/sys/dnode.h

@@ -424,6 +424,7 @@ int dnode_next_offset(dnode_t *dn, int flags, uint64_t *off,
     int minlvl, uint64_t blkfill, uint64_t txg);
 void dnode_evict_dbufs(dnode_t *dn);
 void dnode_evict_bonus(dnode_t *dn);
+void dnode_free_interior_slots(dnode_t *dn);
 
 #define	DNODE_IS_CACHEABLE(_dn)						\
 	((_dn)->dn_objset->os_primary_cache == ZFS_CACHE_ALL ||		\
@@ -517,6 +518,11 @@ typedef struct dnode_stats {
 	 * which had already been unlinked in an earlier txg.
 	 */
 	kstat_named_t dnode_hold_free_txg;
+	/*
+	 * Number of times dnode_free_interior_slots() needed to retry
+	 * acquiring a slot zrl lock due to contention.
+	 */
+	kstat_named_t dnode_free_interior_lock_retry;
 	/*
 	 * Number of new dnodes allocated by dnode_allocate().
 	 */

module/zfs/dmu_object.c

@@ -275,7 +275,6 @@ dmu_object_reclaim_dnsize(objset_t *os, uint64_t object, dmu_object_type_t ot,
 	return (err);
 }
 
-
 int
 dmu_object_free(objset_t *os, uint64_t object, dmu_tx_t *tx)
 {

module/zfs/dmu_send.c

@@ -2455,10 +2455,8 @@ receive_object(struct receive_writer_arg *rwa, struct drr_object *drro,
 	}
 
 	err = dmu_object_info(rwa->os, drro->drr_object, &doi);
-
-	if (err != 0 && err != ENOENT)
+	if (err != 0 && err != ENOENT && err != EEXIST)
 		return (SET_ERROR(EINVAL));
-	object = err == 0 ? drro->drr_object : DMU_NEW_OBJECT;
 
 	if (drro->drr_object > rwa->max_object)
 		rwa->max_object = drro->drr_object;
@@ -2476,6 +2474,8 @@ receive_object(struct receive_writer_arg *rwa, struct drr_object *drro,
 		int nblkptr = deduce_nblkptr(drro->drr_bonustype,
 		    drro->drr_bonuslen);
 
+		object = drro->drr_object;
+
 		/* nblkptr will be bounded by the bonus size and type */
 		if (rwa->raw && nblkptr != drro->drr_nblkptr)
 			return (SET_ERROR(EINVAL));
@@ -2484,18 +2484,89 @@ receive_object(struct receive_writer_arg *rwa, struct drr_object *drro,
 		    (drro->drr_blksz != doi.doi_data_block_size ||
 		    nblkptr < doi.doi_nblkptr ||
 		    indblksz != doi.doi_metadata_block_size ||
-		    drro->drr_nlevels < doi.doi_indirection)) {
+		    drro->drr_nlevels < doi.doi_indirection ||
+		    drro->drr_dn_slots != doi.doi_dnodesize >> DNODE_SHIFT)) {
 			err = dmu_free_long_range_raw(rwa->os,
 			    drro->drr_object, 0, DMU_OBJECT_END);
 			if (err != 0)
 				return (SET_ERROR(EINVAL));
 		} else if (drro->drr_blksz != doi.doi_data_block_size ||
-		    nblkptr < doi.doi_nblkptr) {
+		    nblkptr < doi.doi_nblkptr ||
+		    drro->drr_dn_slots != doi.doi_dnodesize >> DNODE_SHIFT) {
 			err = dmu_free_long_range(rwa->os, drro->drr_object,
 			    0, DMU_OBJECT_END);
 			if (err != 0)
 				return (SET_ERROR(EINVAL));
 		}
+
+		/*
+		 * The dmu does not currently support decreasing nlevels
+		 * on an object. For non-raw sends, this does not matter
+		 * and the new object can just use the previous one's nlevels.
+		 * For raw sends, however, the structure of the received dnode
+		 * (including nlevels) must match that of the send side.
+		 * Therefore, instead of using dmu_object_reclaim(), we must
+		 * free the object completely and call dmu_object_claim_dnsize()
+		 * instead.
+		 */
+		if ((rwa->raw && drro->drr_nlevels < doi.doi_indirection) ||
+		    drro->drr_dn_slots != doi.doi_dnodesize >> DNODE_SHIFT) {
+			if (rwa->raw) {
+				err = dmu_free_long_object_raw(rwa->os,
+				    drro->drr_object);
+			} else {
+				err = dmu_free_long_object(rwa->os,
+				    drro->drr_object);
+			}
+			if (err != 0)
+				return (SET_ERROR(EINVAL));
+
+			txg_wait_synced(dmu_objset_pool(rwa->os), 0);
+			object = DMU_NEW_OBJECT;
+		}
+	} else if (err == EEXIST) {
+		/*
+		 * The object requested is currently an interior slot of a
+		 * multi-slot dnode. This will be resolved when the next txg
+		 * is synced out, since the send stream will have told us
+		 * to free this slot when we freed the associated dnode
+		 * earlier in the stream.
+		 */
+		txg_wait_synced(dmu_objset_pool(rwa->os), 0);
+		object = drro->drr_object;
+	} else {
+		/* object is free and we are about to allocate a new one */
+		object = DMU_NEW_OBJECT;
+	}
+
+	/*
+	 * If this is a multi-slot dnode there is a chance that this
+	 * object will expand into a slot that is already used by
+	 * another object from the previous snapshot. We must free
+	 * these objects before we attempt to allocate the new dnode.
+	 */
+	if (drro->drr_dn_slots > 1) {
+		for (uint64_t slot = drro->drr_object + 1;
+		    slot < drro->drr_object + drro->drr_dn_slots;
+		    slot++) {
+			dmu_object_info_t slot_doi;
+
+			err = dmu_object_info(rwa->os, slot, &slot_doi);
+			if (err == ENOENT || err == EEXIST)
+				continue;
+			else if (err != 0)
+				return (err);
+
+			if (rwa->raw)
+				err = dmu_free_long_object_raw(rwa->os, slot);
+			else
+				err = dmu_free_long_object(rwa->os, slot);
+
+			if (err != 0)
+				return (err);
+		}
+
+		txg_wait_synced(dmu_objset_pool(rwa->os), 0);
 	}
 
 	tx = dmu_tx_create(rwa->os);
@@ -2849,6 +2920,7 @@ receive_spill(struct receive_writer_arg *rwa, struct drr_spill *drrs,
 		dmu_tx_abort(tx);
 		return (err);
 	}
+
 	if (rwa->raw) {
 		VERIFY0(dmu_object_dirty_raw(rwa->os, drrs->drr_object, tx));
 		dmu_buf_will_change_crypt_params(db_spill, tx);
@@ -3199,7 +3271,7 @@ receive_read_record(struct receive_arg *ra)
 		 * See receive_read_prefetch for an explanation why we're
 		 * storing this object in the ignore_obj_list.
 		 */
-		if (err == ENOENT ||
+		if (err == ENOENT || err == EEXIST ||
 		    (err == 0 && doi.doi_data_block_size != drro->drr_blksz)) {
 			objlist_insert(&ra->ignore_objlist, drro->drr_object);
 			err = 0;

module/zfs/dnode.c

@@ -55,6 +55,7 @@ dnode_stats_t dnode_stats = {
 	{ "dnode_hold_free_overflow",		KSTAT_DATA_UINT64 },
 	{ "dnode_hold_free_refcount",		KSTAT_DATA_UINT64 },
 	{ "dnode_hold_free_txg",		KSTAT_DATA_UINT64 },
+	{ "dnode_free_interior_lock_retry",	KSTAT_DATA_UINT64 },
 	{ "dnode_allocate",			KSTAT_DATA_UINT64 },
 	{ "dnode_reallocate",			KSTAT_DATA_UINT64 },
 	{ "dnode_buf_evict",			KSTAT_DATA_UINT64 },
@@ -518,6 +519,7 @@ dnode_destroy(dnode_t *dn)
 	mutex_exit(&os->os_lock);
 
 	/* the dnode can no longer move, so we can release the handle */
+	if (!zrl_is_locked(&dn->dn_handle->dnh_zrlock))
 		zrl_remove(&dn->dn_handle->dnh_zrlock);
 
 	dn->dn_allocated_txg = 0;
@@ -665,6 +667,8 @@ dnode_reallocate(dnode_t *dn, dmu_object_type_t ot, int blocksize,
 	    DN_BONUS_SIZE(spa_maxdnodesize(dmu_objset_spa(dn->dn_objset))));
 
 	dn_slots = dn_slots > 0 ? dn_slots : DNODE_MIN_SLOTS;
+
+	dnode_free_interior_slots(dn);
 	DNODE_STAT_BUMP(dnode_reallocate);
 
 	/* clean up any unreferenced dbufs */
@@ -1067,19 +1071,73 @@ dnode_set_slots(dnode_children_t *children, int idx, int slots, void *ptr)
 }
 
 static boolean_t
-dnode_check_slots(dnode_children_t *children, int idx, int slots, void *ptr)
+dnode_check_slots_free(dnode_children_t *children, int idx, int slots)
 {
 	ASSERT3S(idx + slots, <=, DNODES_PER_BLOCK);
 
 	for (int i = idx; i < idx + slots; i++) {
 		dnode_handle_t *dnh = &children->dnc_children[i];
-		if (dnh->dnh_dnode != ptr)
+		dnode_t *dn = dnh->dnh_dnode;
+
+		if (dn == DN_SLOT_FREE) {
+			continue;
+		} else if (DN_SLOT_IS_PTR(dn)) {
+			mutex_enter(&dn->dn_mtx);
+			dmu_object_type_t type = dn->dn_type;
+			mutex_exit(&dn->dn_mtx);
+
+			if (type != DMU_OT_NONE)
+				return (B_FALSE);
+
+			continue;
+		} else {
+			return (B_FALSE);
+		}
+
 		return (B_FALSE);
 	}
 
 	return (B_TRUE);
 }
 
+static void
+dnode_reclaim_slots(dnode_children_t *children, int idx, int slots)
+{
+	ASSERT3S(idx + slots, <=, DNODES_PER_BLOCK);
+
+	for (int i = idx; i < idx + slots; i++) {
+		dnode_handle_t *dnh = &children->dnc_children[i];
+
+		ASSERT(zrl_is_locked(&dnh->dnh_zrlock));
+
+		if (DN_SLOT_IS_PTR(dnh->dnh_dnode)) {
+			ASSERT3S(dnh->dnh_dnode->dn_type, ==, DMU_OT_NONE);
+			dnode_destroy(dnh->dnh_dnode);
+			dnh->dnh_dnode = DN_SLOT_FREE;
+		}
+	}
+}
+
+void
+dnode_free_interior_slots(dnode_t *dn)
+{
+	dnode_children_t *children = dmu_buf_get_user(&dn->dn_dbuf->db);
+	int epb = dn->dn_dbuf->db.db_size >> DNODE_SHIFT;
+	int idx = (dn->dn_object & (epb - 1)) + 1;
+	int slots = dn->dn_num_slots - 1;
+
+	if (slots == 0)
+		return;
+
+	ASSERT3S(idx + slots, <=, DNODES_PER_BLOCK);
+
+	while (!dnode_slots_tryenter(children, idx, slots))
+		DNODE_STAT_BUMP(dnode_free_interior_lock_retry);
+
+	dnode_set_slots(children, idx, slots, DN_SLOT_FREE);
+	dnode_slots_rele(children, idx, slots);
+}
+
 void
 dnode_special_close(dnode_handle_t *dnh)
 {
@@ -1377,7 +1435,7 @@ dnode_hold_impl(objset_t *os, uint64_t object, int flag, int slots,
 		while (dn == DN_SLOT_UNINIT) {
 			dnode_slots_hold(dnc, idx, slots);
 
-			if (!dnode_check_slots(dnc, idx, slots, DN_SLOT_FREE)) {
+			if (!dnode_check_slots_free(dnc, idx, slots)) {
 				DNODE_STAT_BUMP(dnode_hold_free_misses);
 				dnode_slots_rele(dnc, idx, slots);
 				dbuf_rele(db, FTAG);
@@ -1390,15 +1448,29 @@ dnode_hold_impl(objset_t *os, uint64_t object, int flag, int slots,
 				continue;
 			}
 
-			if (!dnode_check_slots(dnc, idx, slots, DN_SLOT_FREE)) {
+			if (!dnode_check_slots_free(dnc, idx, slots)) {
 				DNODE_STAT_BUMP(dnode_hold_free_lock_misses);
 				dnode_slots_rele(dnc, idx, slots);
 				dbuf_rele(db, FTAG);
 				return (SET_ERROR(ENOSPC));
 			}
 
+			/*
+			 * Allocated but otherwise free dnodes which would
+			 * be in the interior of a multi-slot dnodes need
+			 * to be freed.  Single slot dnodes can be safely
+			 * re-purposed as a performance optimization.
+			 */
+			if (slots > 1)
+				dnode_reclaim_slots(dnc, idx + 1, slots - 1);
+
 			dnh = &dnc->dnc_children[idx];
-			dn = dnode_create(os, dn_block + idx, db, object, dnh);
+			if (DN_SLOT_IS_PTR(dnh->dnh_dnode)) {
+				dn = dnh->dnh_dnode;
+			} else {
+				dn = dnode_create(os, dn_block + idx, db,
+				    object, dnh);
+			}
 		}
 
 		mutex_enter(&dn->dn_mtx);

module/zfs/dnode_sync.c

@@ -529,6 +529,7 @@ dnode_sync_free(dnode_t *dn, dmu_tx_t *tx)
 	if (dn->dn_allocated_txg != dn->dn_free_txg)
 		dmu_buf_will_dirty(&dn->dn_dbuf->db, tx);
 	bzero(dn->dn_phys, sizeof (dnode_phys_t) * dn->dn_num_slots);
+	dnode_free_interior_slots(dn);
 
 	mutex_enter(&dn->dn_mtx);
 	dn->dn_type = DMU_OT_NONE;
@@ -536,6 +537,7 @@ dnode_sync_free(dnode_t *dn, dmu_tx_t *tx)
 	dn->dn_allocated_txg = 0;
 	dn->dn_free_txg = 0;
 	dn->dn_have_spill = B_FALSE;
+	dn->dn_num_slots = 1;
 	mutex_exit(&dn->dn_mtx);
 
 	ASSERT(dn->dn_object != DMU_META_DNODE_OBJECT);

tests/runfiles/linux.run

@@ -657,7 +657,7 @@ tests = ['rsend_001_pos', 'rsend_002_pos', 'rsend_003_pos', 'rsend_004_pos',
     'send-c_mixed_compression', 'send-c_stream_size_estimate', 'send-cD',
     'send-c_embedded_blocks', 'send-c_resume', 'send-cpL_varied_recsize',
     'send-c_recv_dedup', 'send_encrypted_files', 'send_encrypted_heirarchy',
-    'send_freeobjects']
+    'send_freeobjects', 'send_realloc_dnode_size']
 tags = ['functional', 'rsend']
 
 [tests/functional/scrub_mirror]

tests/zfs-tests/tests/functional/rsend/Makefile.am

@@ -40,4 +40,5 @@ dist_pkgdata_SCRIPTS = \
 	send-c_volume.ksh \
 	send-c_zstreamdump.ksh \
 	send-cpL_varied_recsize.ksh \
-	send_freeobjects.ksh
+	send_freeobjects.ksh \
+	send_realloc_dnode_size.ksh

tests/zfs-tests/tests/functional/rsend/send_realloc_dnode_size.ksh

@@ -0,0 +1,98 @@
+#!/bin/ksh
+
+#
+# This file and its contents are supplied under the terms of the
+# Common Development and Distribution License ("CDDL"), version 1.0.
+# You may only use this file in accordance with the terms of version
+# 1.0 of the CDDL.
+#
+# A full copy of the text of the CDDL should have accompanied this
+# source.  A copy of the CDDL is also available via the Internet at
+# http://www.illumos.org/license/CDDL.
+#
+
+#
+# Copyright (c) 2017 by Lawrence Livermore National Security, LLC.
+#
+
+. $STF_SUITE/include/libtest.shlib
+. $STF_SUITE/tests/functional/rsend/rsend.kshlib
+
+#
+# Description:
+# Verify incremental receive properly handles objects with changed
+# dnode slot count.
+#
+# Strategy:
+# 1. Populate a dataset with 1k byte dnodes and snapshot
+# 2. Remove objects, set dnodesize=legacy, and remount dataset so new objects
+#    get recycled numbers and formerly "interior" dnode slots get assigned
+#    to new objects
+# 3. Remove objects, set dnodesize=2k, and remount dataset so new objects
+#    overlap with recently recycled and formerly "normal" dnode slots get
+#    assigned to new objects
+# 4. Generate initial and incremental streams
+# 5. Verify initial and incremental streams can be received
+#
+
+verify_runnable "both"
+
+log_assert "Verify incremental receive handles objects with changed dnode size"
+
+function cleanup
+{
+	rm -f $BACKDIR/fs-dn-legacy
+	rm -f $BACKDIR/fs-dn-1k
+	rm -f $BACKDIR/fs-dn-2k
+
+	if datasetexists $POOL/fs ; then
+		log_must zfs destroy -rR $POOL/fs
+	fi
+
+	if datasetexists $POOL/newfs ; then
+		log_must zfs destroy -rR $POOL/newfs
+	fi
+}
+
+log_onexit cleanup
+
+# 1. Populate a dataset with 1k byte dnodes and snapshot
+log_must zfs create -o dnodesize=1k $POOL/fs
+log_must mk_files 200 262144 0 $POOL/fs
+log_must zfs snapshot $POOL/fs@a
+
+# 2. Remove objects, set dnodesize=legacy, and remount dataset so new objects
+#    get recycled numbers and formerly "interior" dnode slots get assigned
+#    to new objects
+rm /$POOL/fs/*
+
+log_must zfs unmount $POOL/fs
+log_must zfs set dnodesize=legacy $POOL/fs
+log_must zfs mount $POOL/fs
+
+log_must mk_files 200 262144 0 $POOL/fs
+log_must zfs snapshot $POOL/fs@b
+
+# 3. Remove objects, set dnodesize=2k, and remount dataset so new objects
+#    overlap with recently recycled and formerly "normal" dnode slots get
+#    assigned to new objects
+rm /$POOL/fs/*
+
+log_must zfs unmount $POOL/fs
+log_must zfs set dnodesize=2k $POOL/fs
+log_must zfs mount $POOL/fs
+
+mk_files 200 262144 0 $POOL/fs
+log_must zfs snapshot $POOL/fs@c
+
+# 4. Generate initial and incremental streams
+log_must eval "zfs send $POOL/fs@a > $BACKDIR/fs-dn-1k"
+log_must eval "zfs send -i $POOL/fs@a $POOL/fs@b > $BACKDIR/fs-dn-legacy"
+log_must eval "zfs send -i $POOL/fs@b $POOL/fs@c > $BACKDIR/fs-dn-2k"
+
+# 5. Verify initial and incremental streams can be received
+log_must eval "zfs recv $POOL/newfs < $BACKDIR/fs-dn-1k"
+log_must eval "zfs recv $POOL/newfs < $BACKDIR/fs-dn-legacy"
+log_must eval "zfs recv $POOL/newfs < $BACKDIR/fs-dn-2k"
+
+log_pass "Verify incremental receive handles objects with changed dnode size"