Raw receives must compress metadnode blocks

Currently, the DMU relies on ZIO layer compression to free LO dnode blocks that no longer have objects in them. However, raw receives disable all compression, meaning that these blocks can never be freed. In addition to the obvious space concerns, this could also cause incremental raw receives to fail to mount since the MAC of a hole is different from that of a completely zeroed block. This patch corrects this issue by adding a special case in zio_write_compress() which will attempt to compress these blocks to a hole even if ZIO_FLAG_RAW_ENCRYPT is set. This patch also removes the zfs_mdcomp_disable tunable, since tuning it could cause these same issues. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Tom Caputi <tcaputi@datto.com>
openzfsonosx · Jul 12, 2018 · 5f27a49 · 5f27a49
1 parent 61f53ad
commit 5f27a49
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diff --git a/man/man5/zfs-module-parameters.5 b/man/man5/zfs-module-parameters.5
@@ -1144,17 +1144,6 @@ regardless of this setting.
 Default value: \fB1,048,576\fR.
 .RE
 
-.sp
-.ne 2
-.na
-\fBzfs_mdcomp_disable\fR (int)
-.ad
-.RS 12n
-Disable meta data compression
-.sp
-Use \fB1\fR for yes and \fB0\fR for no (default).
-.RE
-
 .sp
 .ne 2
 .na

diff --git a/module/zfs/dbuf.c b/module/zfs/dbuf.c
@@ -3477,7 +3477,7 @@ dbuf_prepare_encrypted_dnode_leaf(dbuf_dirty_record_t *dr)
 		    dmu_objset_id(db->db_objset),
 		    dr->dt.dl.dr_byteorder, DMU_OT_DNODE,
 		    dr->dt.dl.dr_salt, dr->dt.dl.dr_iv, dr->dt.dl.dr_mac);
-	}
+        }
 }
 
 /*

diff --git a/module/zfs/dmu.c b/module/zfs/dmu.c
@@ -2400,16 +2400,12 @@ dmu_write_policy(objset_t *os, dnode_t *dn, int level, int wp, zio_prop_t *zp)
 	 *	 3. all other level 0 blocks
 	 */
 	if (ismd) {
-		if (zfs_mdcomp_disable) {
-			compress = ZIO_COMPRESS_EMPTY;
-		} else {
-			/*
-			 * XXX -- we should design a compression algorithm
-			 * that specializes in arrays of bps.
-			 */
-			compress = zio_compress_select(os->os_spa,
-			    ZIO_COMPRESS_ON, ZIO_COMPRESS_ON);
-		}
+		/*
+		 * XXX -- we should design a compression algorithm
+		 * that specializes in arrays of bps.
+		 */
+		compress = zio_compress_select(os->os_spa,
+		    ZIO_COMPRESS_ON, ZIO_COMPRESS_ON);
 
 		/*
 		 * Metadata always gets checksummed.  If the data

diff --git a/module/zfs/zio.c b/module/zfs/zio.c
@@ -1630,6 +1630,19 @@ zio_write_compress(zio_t *zio)
 		*bp = zio->io_bp_orig;
 		zio->io_pipeline = zio->io_orig_pipeline;
 
+	} else if ((zio->io_flags & ZIO_FLAG_RAW_ENCRYPT) != 0 &&
+	    zp->zp_type == DMU_OT_DNODE) {
+		/*
+		 * The DMU actually relies on the zio layer's compression
+		 * to free metadnode blocks that have had all contained
+		 * dnodes freed. As a result, even when doing a raw
+		 * receive, we must check whether the block can be compressed
+		 * to a hole.
+		 */
+		psize = zio_compress_data(ZIO_COMPRESS_EMPTY,
+		    zio->io_abd, NULL, lsize);
+		if (psize == 0)
+			compress = ZIO_COMPRESS_OFF;
 	} else {
 		ASSERT3U(psize, !=, 0);
 	}

diff --git a/tests/zfs-tests/tests/functional/rsend/send_encrypted_files.ksh b/tests/zfs-tests/tests/functional/rsend/send_encrypted_files.ksh
@@ -74,12 +74,6 @@ log_must mkfile -n 32M /$TESTPOOL/$TESTFS2/truncated
 log_must truncate -s 4M /$TESTPOOL/$TESTFS2/truncated
 sync
 
-log_must set_metadata_compression_disabled 1
-log_must dd if=/dev/urandom of=/$TESTPOOL/$TESTFS2/no_mdcomp \
-	count=1 bs=512 seek=10G >/dev/null 2>&1
-sync
-log_must set_metadata_compression_disabled 0
-
 log_must mkdir -p /$TESTPOOL/$TESTFS2/dir
 for i in {1..1000}; do
 	log_must mkfile 512 /$TESTPOOL/$TESTFS2/dir/file-$i