Add ability to recompress send streams with new compression algorithm

As new compression algorithms are added to ZFS, it could be useful for 
people to recompress data with new algorithms. There is currently no 
mechanism to do this aside from copying the data manually into a new 
filesystem with the new algorithm enabled. This tool allows the 
transformation to happen through zfs send, allowing it to be done 
efficiently to remote systems and in an incremental fashion.

A new zstream command is added that decompresses WRITE records and 
then recompresses them with a provided algorithm, and then re-emits 
the modified send stream. It may also be possible to re-compress 
embedded block pointers, but that was not attempted for the initial 
version.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Matthew Ahrens <mahrens@delphix.com>
Signed-off-by: Paul Dagnelie <pcd@delphix.com>
Closes #14106

cmd/zstream/Makefile.am

@@ -6,6 +6,7 @@ zstream_SOURCES = \
 	%D%/zstream.h \
 	%D%/zstream_decompress.c \
 	%D%/zstream_dump.c \
+	%D%/zstream_recompress.c \
 	%D%/zstream_redup.c \
 	%D%/zstream_token.c
 

cmd/zstream/zstream.c

@@ -42,6 +42,8 @@ zstream_usage(void)
 	    "\n"
 	    "\tzstream decompress [-v] [OBJECT,OFFSET[,TYPE]] ...\n"
 	    "\n"
+	    "\tzstream recompress [ -l level] TYPE\n"
+	    "\n"
 	    "\tzstream token resume_token\n"
 	    "\n"
 	    "\tzstream redup [-v] FILE | ...\n");
@@ -65,6 +67,8 @@ main(int argc, char *argv[])
 		return (zstream_do_dump(argc - 1, argv + 1));
 	} else if (strcmp(subcommand, "decompress") == 0) {
 		return (zstream_do_decompress(argc - 1, argv + 1));
+	} else if (strcmp(subcommand, "recompress") == 0) {
+		return (zstream_do_recompress(argc - 1, argv + 1));
 	} else if (strcmp(subcommand, "token") == 0) {
 		return (zstream_do_token(argc - 1, argv + 1));
 	} else if (strcmp(subcommand, "redup") == 0) {

cmd/zstream/zstream.h

@@ -30,6 +30,7 @@ extern void *safe_malloc(size_t size);
 extern int zstream_do_redup(int, char *[]);
 extern int zstream_do_dump(int, char *[]);
 extern int zstream_do_decompress(int argc, char *argv[]);
+extern int zstream_do_recompress(int argc, char *argv[]);
 extern int zstream_do_token(int, char *[]);
 extern void zstream_usage(void);
 

cmd/zstream/zstream_recompress.c

@@ -0,0 +1,356 @@
+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
+ *
+ * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+ * or https://opensource.org/licenses/CDDL-1.0.
+ * See the License for the specific language governing permissions
+ * and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+
+/*
+ * Copyright 2022 Axcient.  All rights reserved.
+ * Use is subject to license terms.
+ */
+
+/*
+ * Copyright (c) 2022 by Delphix. All rights reserved.
+ */
+
+#include <err.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/zfs_ioctl.h>
+#include <sys/zio_checksum.h>
+#include <sys/zstd/zstd.h>
+#include "zfs_fletcher.h"
+#include "zstream.h"
+
+static int
+dump_record(dmu_replay_record_t *drr, void *payload, int payload_len,
+    zio_cksum_t *zc, int outfd)
+{
+	assert(offsetof(dmu_replay_record_t, drr_u.drr_checksum.drr_checksum)
+	    == sizeof (dmu_replay_record_t) - sizeof (zio_cksum_t));
+	fletcher_4_incremental_native(drr,
+	    offsetof(dmu_replay_record_t, drr_u.drr_checksum.drr_checksum), zc);
+	if (drr->drr_type != DRR_BEGIN) {
+		assert(ZIO_CHECKSUM_IS_ZERO(&drr->drr_u.
+		    drr_checksum.drr_checksum));
+		drr->drr_u.drr_checksum.drr_checksum = *zc;
+	}
+	fletcher_4_incremental_native(&drr->drr_u.drr_checksum.drr_checksum,
+	    sizeof (zio_cksum_t), zc);
+	if (write(outfd, drr, sizeof (*drr)) == -1)
+		return (errno);
+	if (payload_len != 0) {
+		fletcher_4_incremental_native(payload, payload_len, zc);
+		if (write(outfd, payload, payload_len) == -1)
+			return (errno);
+	}
+	return (0);
+}
+
+int
+zstream_do_recompress(int argc, char *argv[])
+{
+	int bufsz = SPA_MAXBLOCKSIZE;
+	char *buf = safe_malloc(bufsz);
+	dmu_replay_record_t thedrr;
+	dmu_replay_record_t *drr = &thedrr;
+	zio_cksum_t stream_cksum;
+	int c;
+	int level = -1;
+
+	while ((c = getopt(argc, argv, "l:")) != -1) {
+		switch (c) {
+		case 'l':
+			if (sscanf(optarg, "%d", &level) != 0) {
+				fprintf(stderr,
+				    "failed to parse level '%s'\n",
+				    optarg);
+				zstream_usage();
+			}
+			break;
+		case '?':
+			(void) fprintf(stderr, "invalid option '%c'\n",
+			    optopt);
+			zstream_usage();
+			break;
+		}
+	}
+
+	argc -= optind;
+	argv += optind;
+
+	if (argc != 1)
+		zstream_usage();
+	int type = 0;
+	zio_compress_info_t *cinfo = NULL;
+	if (0 == strcmp(argv[0], "off")) {
+		type = ZIO_COMPRESS_OFF;
+		cinfo = &zio_compress_table[type];
+	} else if (0 == strcmp(argv[0], "inherit") ||
+	    0 == strcmp(argv[0], "empty") ||
+	    0 == strcmp(argv[0], "on")) {
+		// Fall through to invalid compression type case
+	} else {
+		for (int i = 0; i < ZIO_COMPRESS_FUNCTIONS; i++) {
+			if (0 == strcmp(zio_compress_table[i].ci_name,
+			    argv[0])) {
+				cinfo = &zio_compress_table[i];
+				type = i;
+				break;
+			}
+		}
+	}
+	if (cinfo == NULL) {
+		fprintf(stderr, "Invalid compression type %s.\n",
+		    argv[0]);
+		exit(2);
+	}
+
+	if (cinfo->ci_compress == NULL) {
+		type = 0;
+		cinfo = &zio_compress_table[0];
+	}
+
+	if (isatty(STDIN_FILENO)) {
+		(void) fprintf(stderr,
+		    "Error: The send stream is a binary format "
+		    "and can not be read from a\n"
+		    "terminal.  Standard input must be redirected.\n");
+		exit(1);
+	}
+
+	fletcher_4_init();
+	zio_init();
+	zstd_init();
+	while (sfread(drr, sizeof (*drr), stdin) != 0) {
+		struct drr_write *drrw;
+		uint64_t payload_size = 0;
+
+		/*
+		 * We need to regenerate the checksum.
+		 */
+		if (drr->drr_type != DRR_BEGIN) {
+			memset(&drr->drr_u.drr_checksum.drr_checksum, 0,
+			    sizeof (drr->drr_u.drr_checksum.drr_checksum));
+		}
+
+
+		switch (drr->drr_type) {
+		case DRR_BEGIN:
+		{
+			ZIO_SET_CHECKSUM(&stream_cksum, 0, 0, 0, 0);
+
+			int sz = drr->drr_payloadlen;
+			if (sz != 0) {
+				if (sz > bufsz) {
+					buf = realloc(buf, sz);
+					if (buf == NULL)
+						err(1, "realloc");
+					bufsz = sz;
+				}
+				(void) sfread(buf, sz, stdin);
+			}
+			payload_size = sz;
+			break;
+		}
+		case DRR_END:
+		{
+			struct drr_end *drre = &drr->drr_u.drr_end;
+			/*
+			 * Use the recalculated checksum, unless this is
+			 * the END record of a stream package, which has
+			 * no checksum.
+			 */
+			if (!ZIO_CHECKSUM_IS_ZERO(&drre->drr_checksum))
+				drre->drr_checksum = stream_cksum;
+			break;
+		}
+
+		case DRR_OBJECT:
+		{
+			struct drr_object *drro = &drr->drr_u.drr_object;
+
+			if (drro->drr_bonuslen > 0) {
+				payload_size = DRR_OBJECT_PAYLOAD_SIZE(drro);
+				(void) sfread(buf, payload_size, stdin);
+			}
+			break;
+		}
+
+		case DRR_SPILL:
+		{
+			struct drr_spill *drrs = &drr->drr_u.drr_spill;
+			payload_size = DRR_SPILL_PAYLOAD_SIZE(drrs);
+			(void) sfread(buf, payload_size, stdin);
+			break;
+		}
+
+		case DRR_WRITE_BYREF:
+			fprintf(stderr,
+			    "Deduplicated streams are not supported\n");
+			exit(1);
+			break;
+
+		case DRR_WRITE:
+		{
+			drrw = &thedrr.drr_u.drr_write;
+			payload_size = DRR_WRITE_PAYLOAD_SIZE(drrw);
+			/*
+			 * In order to recompress an encrypted block, you have
+			 * to decrypt, decompress, recompress, and
+			 * re-encrypt. That can be a future enhancement (along
+			 * with decryption or re-encryption), but for now we
+			 * skip encrypted blocks.
+			 */
+			boolean_t encrypted = B_FALSE;
+			for (int i = 0; i < ZIO_DATA_SALT_LEN; i++) {
+				if (drrw->drr_salt[i] != 0) {
+					encrypted = B_TRUE;
+					break;
+				}
+			}
+			if (encrypted) {
+				(void) sfread(buf, payload_size, stdin);
+				break;
+			}
+			if (drrw->drr_compressiontype >=
+			    ZIO_COMPRESS_FUNCTIONS) {
+				fprintf(stderr, "Invalid compression type in "
+				    "stream: %d\n", drrw->drr_compressiontype);
+				exit(3);
+			}
+			zio_compress_info_t *dinfo =
+			    &zio_compress_table[drrw->drr_compressiontype];
+
+			/* Set up buffers to minimize memcpys */
+			char *cbuf, *dbuf;
+			if (cinfo->ci_compress == NULL)
+				dbuf = buf;
+			else
+				dbuf = safe_calloc(bufsz);
+
+			if (dinfo->ci_decompress == NULL)
+				cbuf = dbuf;
+			else
+				cbuf = safe_calloc(payload_size);
+
+			/* Read and decompress the payload */
+			(void) sfread(cbuf, payload_size, stdin);
+			if (dinfo->ci_decompress != NULL) {
+				if (0 != dinfo->ci_decompress(cbuf, dbuf,
+				    payload_size, MIN(bufsz,
+				    drrw->drr_logical_size), dinfo->ci_level)) {
+					warnx("decompression type %d failed "
+					    "for ino %llu offset %llu",
+					    type,
+					    (u_longlong_t)drrw->drr_object,
+					    (u_longlong_t)drrw->drr_offset);
+					exit(4);
+				}
+				payload_size = drrw->drr_logical_size;
+				free(cbuf);
+			}
+
+			/* Recompress the payload */
+			if (cinfo->ci_compress != NULL) {
+				payload_size = P2ROUNDUP(cinfo->ci_compress(
+				    dbuf, buf, drrw->drr_logical_size,
+				    MIN(payload_size, bufsz), (level == -1 ?
+				    cinfo->ci_level : level)),
+				    SPA_MINBLOCKSIZE);
+				if (payload_size != drrw->drr_logical_size) {
+					drrw->drr_compressiontype = type;
+					drrw->drr_compressed_size =
+					    payload_size;
+				} else {
+					memcpy(buf, dbuf, payload_size);
+					drrw->drr_compressiontype = 0;
+					drrw->drr_compressed_size = 0;
+				}
+				free(dbuf);
+			} else {
+				drrw->drr_compressiontype = type;
+				drrw->drr_compressed_size = 0;
+			}
+			break;
+		}
+
+		case DRR_WRITE_EMBEDDED:
+		{
+			struct drr_write_embedded *drrwe =
+			    &drr->drr_u.drr_write_embedded;
+			payload_size =
+			    P2ROUNDUP((uint64_t)drrwe->drr_psize, 8);
+			(void) sfread(buf, payload_size, stdin);
+			break;
+		}
+
+		case DRR_FREEOBJECTS:
+		case DRR_FREE:
+		case DRR_OBJECT_RANGE:
+			break;
+
+		default:
+			(void) fprintf(stderr, "INVALID record type 0x%x\n",
+			    drr->drr_type);
+			/* should never happen, so assert */
+			assert(B_FALSE);
+		}
+
+		if (feof(stdout)) {
+			fprintf(stderr, "Error: unexpected end-of-file\n");
+			exit(1);
+		}
+		if (ferror(stdout)) {
+			fprintf(stderr, "Error while reading file: %s\n",
+			    strerror(errno));
+			exit(1);
+		}
+
+		/*
+		 * We need to recalculate the checksum, and it needs to be
+		 * initially zero to do that.  BEGIN records don't have
+		 * a checksum.
+		 */
+		if (drr->drr_type != DRR_BEGIN) {
+			memset(&drr->drr_u.drr_checksum.drr_checksum, 0,
+			    sizeof (drr->drr_u.drr_checksum.drr_checksum));
+		}
+		if (dump_record(drr, buf, payload_size,
+		    &stream_cksum, STDOUT_FILENO) != 0)
+			break;
+		if (drr->drr_type == DRR_END) {
+			/*
+			 * Typically the END record is either the last
+			 * thing in the stream, or it is followed
+			 * by a BEGIN record (which also zeros the checksum).
+			 * However, a stream package ends with two END
+			 * records.  The last END record's checksum starts
+			 * from zero.
+			 */
+			ZIO_SET_CHECKSUM(&stream_cksum, 0, 0, 0, 0);
+		}
+	}
+	free(buf);
+	fletcher_4_fini();
+	zio_fini();
+	zstd_fini();
+
+	return (0);
+}

man/man8/zstream.8

@@ -43,6 +43,10 @@
 .Nm
 .Cm token
 .Ar resume_token
+.Nm
+.Cm recompress
+.Op Fl l Ar level
+.Ar algorithm
 .
 .Sh DESCRIPTION
 The
@@ -149,6 +153,27 @@ Therefore, a deduplicated send stream can be received by running:
 Verbose.
 Print summary of converted records.
 .El
+.It Xo
+.Nm
+.Cm recompress
+.Op Fl l Ar level
+.Ar algorithm
+.Xc
+Recompresses a send stream, provided on standard input, using the provided
+algorithm and optional level, and writes the modified stream to standard output.
+All WRITE records in the send stream will be recompressed, unless they fail
+to result in size reduction compared to being left uncompressed.
+The provided algorithm can be any valid value to the
+.Nm compress
+property.
+Note that encrypted send streams cannot be recompressed.
+.Bl -tag -width "-l"
+.It Fl l Ar level
+Specifies compression level.
+Only needed for algorithms where the level is not implied as part of the name
+of the algorithm (e.g. gzip-3 does not require it, while zstd does, if a
+non-default level is desired).
+.El
 .El
 .
 .Sh EXAMPLES

tests/runfiles/common.run

@@ -838,12 +838,12 @@ tests = ['recv_dedup', 'recv_dedup_encrypted_zvol', 'rsend_001_pos',
     'rsend_026_neg', 'rsend_027_pos', 'rsend_028_neg', 'rsend_029_neg',
     'rsend_030_pos', 'send-c_verify_ratio', 'send-c_verify_contents',
     'send-c_props', 'send-c_incremental', 'send-c_volume',
-    'send-c_zstreamdump', 'send-c_lz4_disabled', 'send-c_recv_lz4_disabled',
+    'send-c_zstream_recompress', 'send-c_zstreamdump', 'send-c_lz4_disabled',
-    'send-c_mixed_compression', 'send-c_stream_size_estimate',
+    'send-c_recv_lz4_disabled', 'send-c_mixed_compression',
-    'send-c_embedded_blocks', 'send-c_resume', 'send-cpL_varied_recsize',
+    'send-c_stream_size_estimate', 'send-c_embedded_blocks', 'send-c_resume',
-    'send-c_recv_dedup', 'send-L_toggle', 'send_encrypted_hierarchy',
+    'send-cpL_varied_recsize', 'send-c_recv_dedup', 'send-L_toggle',
-    'send_encrypted_props', 'send_encrypted_truncated_files',
+    'send_encrypted_hierarchy', 'send_encrypted_props',
-    'send_freeobjects', 'send_realloc_files',
+    'send_encrypted_truncated_files', 'send_freeobjects', 'send_realloc_files',
     'send_realloc_encrypted_files', 'send_spill_block', 'send_holds',
     'send_hole_birth', 'send_mixed_raw', 'send-wR_encrypted_zvol',
     'send_partial_dataset', 'send_invalid', 'send_doall',

tests/zfs-tests/tests/functional/rsend/send-c_zstream_recompress.ksh

@@ -0,0 +1,58 @@
+#!/bin/ksh -p
+
+#
+# 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) 2022 by Delphix. All rights reserved.
+#
+
+. $STF_SUITE/tests/functional/rsend/rsend.kshlib
+. $STF_SUITE/include/math.shlib
+
+#
+# Description:
+# Verify compression features show up in zstream dump
+#
+# Strategy:
+# 1. Create a compressed send stream
+# 2. Recompress the stream with a different algorithm
+# 3. Verify it can be received correctly
+# 4. Verify the contents match the original filesystem
+# 5. Create an uncompressed send stream
+# 6. Compress the send stream
+# 7. Verify that the stream is smaller when compressed
+#
+
+verify_runnable "both"
+
+log_assert "Verify zstream recompress correctly modifies send streams."
+log_onexit cleanup_pool $POOL2
+
+typeset sendfs=$POOL2/fs
+typeset recvfs=$POOL2/fs2
+
+log_must zfs create -o compress=lz4 $sendfs
+typeset dir=$(get_prop mountpoint $sendfs)
+write_compressible $dir 16m
+log_must zfs snapshot $sendfs@snap
+
+log_must eval "zfs send -c $sendfs@snap | zstream recompress gzip-1 | zfs recv $recvfs"
+typeset recvdir=$(get_prop mountpoint $recvfs)
+log_must diff -r $dir $recvdir
+
+log_must eval "zfs send $sendfs@snap >$BACKDIR/uncompressed"
+log_must zstream recompress gzip-1 <$BACKDIR/uncompressed >$BACKDIR/compressed
+typeset uncomp_size=$(wc -c $BACKDIR/uncompressed | awk '{print $1}')
+typeset comp_size=$(wc -c $BACKDIR/compressed | awk '{print $1}')
+[[ "$uncomp_size" -gt "$comp_size" ]] || log_fail "recompressed stream was not smaller"
+
+log_pass "zstream recompress correctly modifies send streams."