Fix handling of maxblkid for raw sends

Currently, the receive code can create an unreadable dataset from
a correct raw send stream. This is because it is currently
impossible to set maxblkid to a lower value without freeing the
associated object. This means truncating files on the send side
to a non-0 size could result in corruption. This patch solves this
issue by adding a new 'force' flag to dnode_new_blkid() which will
allow the raw receive code to force the DMU to accept the provided
maxblkid even if it is a lower value than the existing one.

For testing purposes the send_encrypted_files.ksh test has been
extended to include a variety of truncated files and multiple
snapshots. It also now leverages the xattrtest command to help
ensure raw receives correctly handle xattrs.

Reviewed-by: Paul Dagnelie <pcd@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Matt Ahrens <mahrens@delphix.com>
Signed-off-by: Tom Caputi <tcaputi@datto.com>
Closes #8168 
Closes #8487

module/zfs/dbuf.c

@@ -2116,7 +2116,8 @@ dbuf_dirty(dmu_buf_impl_t *db, dmu_tx_t *tx)
 	if (db->db_level == 0) {
 		ASSERT(!db->db_objset->os_raw_receive ||
 		    dn->dn_maxblkid >= db->db_blkid);
-		dnode_new_blkid(dn, db->db_blkid, tx, drop_struct_lock);
+		dnode_new_blkid(dn, db->db_blkid, tx,
+		    drop_struct_lock, B_FALSE);
 		ASSERT(dn->dn_maxblkid >= db->db_blkid);
 	}
 

module/zfs/dmu.c

@@ -2155,7 +2155,7 @@ dmu_object_set_maxblkid(objset_t *os, uint64_t object, uint64_t maxblkid,
 	if (err)
 		return (err);
 	rw_enter(&dn->dn_struct_rwlock, RW_WRITER);
-	dnode_new_blkid(dn, maxblkid, tx, B_FALSE);
+	dnode_new_blkid(dn, maxblkid, tx, B_FALSE, B_TRUE);
 	rw_exit(&dn->dn_struct_rwlock);
 	dnode_rele(dn, FTAG);
 	return (0);

module/zfs/dmu_recv.c

@@ -1179,10 +1179,22 @@ receive_object(struct receive_writer_arg *rwa, struct drr_object *drro,
 
 		object = drro->drr_object;
 
-		/* nblkptr will be bounded by the bonus size and type */
+		/* nblkptr should be bounded by the bonus size and type */
 		if (rwa->raw && nblkptr != drro->drr_nblkptr)
 			return (SET_ERROR(EINVAL));
 
+		/*
+		 * Check for indicators that the object was freed and
+		 * reallocated. For all sends, these indicators are:
+		 *     - A changed block size
+		 *     - A smaller nblkptr
+		 *     - A changed dnode size
+		 * For raw sends we also check a few other fields to
+		 * ensure we are preserving the objset structure exactly
+		 * as it was on the receive side:
+		 *     - A changed indirect block size
+		 *     - A smaller nlevels
+		 */
 		if (drro->drr_blksz != doi.doi_data_block_size ||
 		    nblkptr < doi.doi_nblkptr ||
 		    dn_slots != doi.doi_dnodesize >> DNODE_SHIFT ||
@@ -1197,13 +1209,14 @@ receive_object(struct receive_writer_arg *rwa, struct drr_object *drro,
 
 		/*
 		 * 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.
+		 * or changing the number of dnode slots 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 and dnode slots) 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) ||
 		    dn_slots != doi.doi_dnodesize >> DNODE_SHIFT) {
@@ -1214,6 +1227,23 @@ receive_object(struct receive_writer_arg *rwa, struct drr_object *drro,
 			txg_wait_synced(dmu_objset_pool(rwa->os), 0);
 			object = DMU_NEW_OBJECT;
 		}
+
+		/*
+		 * For raw receives, free everything beyond the new incoming
+		 * maxblkid. Normally this would be done with a DRR_FREE
+		 * record that would come after this DRR_OBJECT record is
+		 * processed. However, for raw receives we manually set the
+		 * maxblkid from the drr_maxblkid and so we must first free
+		 * everything above that blkid to ensure the DMU is always
+		 * consistent with itself.
+		 */
+		if (rwa->raw) {
+			err = dmu_free_long_range(rwa->os, drro->drr_object,
+			    (drro->drr_maxblkid + 1) * drro->drr_blksz,
+			    DMU_OBJECT_END);
+			if (err != 0)
+				return (SET_ERROR(EINVAL));
+		}
 	} else if (err == EEXIST) {
 		/*
 		 * The object requested is currently an interior slot of a
@@ -1333,14 +1363,24 @@ receive_object(struct receive_writer_arg *rwa, struct drr_object *drro,
 	/* handle more restrictive dnode structuring for raw recvs */
 	if (rwa->raw) {
 		/*
-		 * Set the indirect block shift and nlevels. This will not fail
-		 * because we ensured all of the blocks were free earlier if
-		 * this is a new object.
+		 * Set the indirect block size, block shift, nlevels.
+		 * This will not fail because we ensured all of the
+		 * blocks were freed earlier if this is a new object.
+		 * For non-new objects block size and indirect block
+		 * shift cannot change and nlevels can only increase.
 		 */
 		VERIFY0(dmu_object_set_blocksize(rwa->os, drro->drr_object,
 		    drro->drr_blksz, drro->drr_indblkshift, tx));
 		VERIFY0(dmu_object_set_nlevels(rwa->os, drro->drr_object,
 		    drro->drr_nlevels, tx));
+
+		/*
+		 * Set the maxblkid. We will never free the first block of
+		 * an object here because a maxblkid of 0 could indicate
+		 * an object with a single block or one with no blocks.
+		 * This will always succeed because we freed all blocks
+		 * beyond the new maxblkid above.
+		 */
 		VERIFY0(dmu_object_set_maxblkid(rwa->os, drro->drr_object,
 		    drro->drr_maxblkid, tx));
 	}

module/zfs/dnode.c

@@ -1828,7 +1828,8 @@ out:
 
 /* read-holding callers must not rely on the lock being continuously held */
 void
-dnode_new_blkid(dnode_t *dn, uint64_t blkid, dmu_tx_t *tx, boolean_t have_read)
+dnode_new_blkid(dnode_t *dn, uint64_t blkid, dmu_tx_t *tx, boolean_t have_read,
+    boolean_t force)
 {
 	int epbs, new_nlevels;
 	uint64_t sz;
@@ -1853,14 +1854,25 @@ dnode_new_blkid(dnode_t *dn, uint64_t blkid, dmu_tx_t *tx, boolean_t have_read)
 		}
 	}
 
-	if (blkid <= dn->dn_maxblkid)
+	/*
+	 * Raw sends (indicated by the force flag) require that we take the
+	 * given blkid even if the value is lower than the current value.
+	 */
+	if (!force && blkid <= dn->dn_maxblkid)
 		goto out;
 
+	/*
+	 * We use the (otherwise unused) top bit of dn_next_maxblkid[txgoff]
+	 * to indicate that this field is set. This allows us to set the
+	 * maxblkid to 0 on an existing object in dnode_sync().
+	 */
 	dn->dn_maxblkid = blkid;
-	dn->dn_next_maxblkid[tx->tx_txg & TXG_MASK] = blkid;
+	dn->dn_next_maxblkid[tx->tx_txg & TXG_MASK] =
+	    blkid | DMU_NEXT_MAXBLKID_SET;
 
 	/*
 	 * Compute the number of levels necessary to support the new maxblkid.
+	 * Raw sends will ensure nlevels is set correctly for us.
 	 */
 	new_nlevels = 1;
 	epbs = dn->dn_indblkshift - SPA_BLKPTRSHIFT;
@@ -1870,8 +1882,12 @@ dnode_new_blkid(dnode_t *dn, uint64_t blkid, dmu_tx_t *tx, boolean_t have_read)
 
 	ASSERT3U(new_nlevels, <=, DN_MAX_LEVELS);
 
-	if (new_nlevels > dn->dn_nlevels)
-		dnode_set_nlevels_impl(dn, new_nlevels, tx);
+	if (!force) {
+		if (new_nlevels > dn->dn_nlevels)
+			dnode_set_nlevels_impl(dn, new_nlevels, tx);
+	} else {
+		ASSERT3U(dn->dn_nlevels, >=, new_nlevels);
+	}
 
 out:
 	if (have_read)

module/zfs/dnode_sync.c

@@ -384,12 +384,7 @@ dnode_sync_free_range_impl(dnode_t *dn, uint64_t blkid, uint64_t nblks,
 		}
 	}
 
-	/*
-	 * Do not truncate the maxblkid if we are performing a raw
-	 * receive. The raw receive sets the mablkid manually and
-	 * must not be overriden.
-	 */
-	if (trunc && !dn->dn_objset->os_raw_receive) {
+	if (trunc) {
 		ASSERTV(uint64_t off);
 		dn->dn_phys->dn_maxblkid = blkid == 0 ? 0 : blkid - 1;
 
@@ -765,11 +760,13 @@ dnode_sync(dnode_t *dn, dmu_tx_t *tx)
 
 	/*
 	 * This must be done after dnode_sync_free_range()
-	 * and dnode_increase_indirection().
+	 * and dnode_increase_indirection(). See dnode_new_blkid()
+	 * for an explanation of the high bit being set.
 	 */
 	if (dn->dn_next_maxblkid[txgoff]) {
 		mutex_enter(&dn->dn_mtx);
-		dnp->dn_maxblkid = dn->dn_next_maxblkid[txgoff];
+		dnp->dn_maxblkid =
+		    dn->dn_next_maxblkid[txgoff] & ~DMU_NEXT_MAXBLKID_SET;
 		dn->dn_next_maxblkid[txgoff] = 0;
 		mutex_exit(&dn->dn_mtx);
 	}

module/zfs/dsl_crypt.c

@@ -2099,7 +2099,7 @@ dsl_crypto_recv_raw_objset_sync(dsl_dataset_t *ds, dmu_objset_type_t ostype,
 	mdn->dn_checksum = checksum;
 
 	rw_enter(&mdn->dn_struct_rwlock, RW_WRITER);
-	dnode_new_blkid(mdn, maxblkid, tx, B_FALSE);
+	dnode_new_blkid(mdn, maxblkid, tx, B_FALSE, B_TRUE);
 	rw_exit(&mdn->dn_struct_rwlock);
 
 	/*