From a1034ee90978042c3c744ef11549cd732dd1dcfd Mon Sep 17 00:00:00 2001
From: Alan Somers <asomers@FreeBSD.org>
Date: Fri, 14 Oct 2022 14:40:00 -0600
Subject: [PATCH] zstream: allow decompress to fix metadata for uncompressed
 records

If a record is uncompressed on-disk but the block pointer insists
otherwise, reading it will return EIO.  This commit adds an "off" type
to the "zstream decompress" command.  Using it will set the compression
field in a zfs stream to "off" without changing the record's data.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Signed-off-by:	Alan Somers <asomers@FreeBSD.org>
Sponsored by:	Axcient
Closes #13997
---
 cmd/zstream/zstream_decompress.c | 38 ++++++++++++++++++++++++++------
 man/man8/zstream.8               |  8 ++++++-
 2 files changed, 38 insertions(+), 8 deletions(-)

diff --git a/cmd/zstream/zstream_decompress.c b/cmd/zstream/zstream_decompress.c
index 31d4b2d36..e5527777b 100644
--- a/cmd/zstream/zstream_decompress.c
+++ b/cmd/zstream/zstream_decompress.c
@@ -115,7 +115,9 @@ zstream_do_decompress(int argc, char *argv[])
 		if (errno || *end != '\0')
 			errx(1, "invalid value for offset");
 		if (argv[i]) {
-			if (0 == strcmp("lz4", argv[i]))
+			if (0 == strcmp("off", argv[i]))
+				type = ZIO_COMPRESS_OFF;
+			else if (0 == strcmp("lz4", argv[i]))
 				type = ZIO_COMPRESS_LZ4;
 			else if (0 == strcmp("lzjb", argv[i]))
 				type = ZIO_COMPRESS_LZJB;
@@ -127,8 +129,8 @@ zstream_do_decompress(int argc, char *argv[])
 				type = ZIO_COMPRESS_ZSTD;
 			else {
 				fprintf(stderr, "Invalid compression type %s.\n"
-				    "Supported types are lz4, lzjb, gzip, zle, "
-				    "and zstd\n",
+				    "Supported types are off, lz4, lzjb, gzip, "
+				    "zle, and zstd\n",
 				    argv[i]);
 				exit(2);
 			}
@@ -240,6 +242,9 @@ zstream_do_decompress(int argc, char *argv[])
 			if (p != NULL) {
 				zio_decompress_func_t *xfunc = NULL;
 				switch ((enum zio_compress)(intptr_t)p->data) {
+				case ZIO_COMPRESS_OFF:
+					xfunc = NULL;
+					break;
 				case ZIO_COMPRESS_LZJB:
 					xfunc = lzjb_decompress;
 					break;
@@ -258,7 +263,6 @@ zstream_do_decompress(int argc, char *argv[])
 				default:
 					assert(B_FALSE);
 				}
-				assert(xfunc != NULL);
 
 
 				/*
@@ -266,12 +270,27 @@ zstream_do_decompress(int argc, char *argv[])
 				 */
 				char *lzbuf = safe_calloc(payload_size);
 				(void) sfread(lzbuf, payload_size, stdin);
-				if (0 != xfunc(lzbuf, buf,
+				if (xfunc == NULL) {
+					memcpy(buf, lzbuf, payload_size);
+					drrw->drr_compressiontype =
+					    ZIO_COMPRESS_OFF;
+					if (verbose)
+						fprintf(stderr, "Resetting "
+						    "compression type to off "
+						    "for ino %llu offset "
+						    "%llu\n",
+						    (u_longlong_t)
+						    drrw->drr_object,
+						    (u_longlong_t)
+						    drrw->drr_offset);
+				} else if (0 != xfunc(lzbuf, buf,
 				    payload_size, payload_size, 0)) {
 					/*
 					 * The block must not be compressed,
-					 * possibly because it gets written
-					 * multiple times in this stream.
+					 * at least not with this compression
+					 * type, possibly because it gets
+					 * written multiple times in this
+					 * stream.
 					 */
 					warnx("decompression failed for "
 					    "ino %llu offset %llu",
@@ -279,11 +298,16 @@ zstream_do_decompress(int argc, char *argv[])
 					    (u_longlong_t)drrw->drr_offset);
 					memcpy(buf, lzbuf, payload_size);
 				} else if (verbose) {
+					drrw->drr_compressiontype =
+					    ZIO_COMPRESS_OFF;
 					fprintf(stderr, "successfully "
 					    "decompressed ino %llu "
 					    "offset %llu\n",
 					    (u_longlong_t)drrw->drr_object,
 					    (u_longlong_t)drrw->drr_offset);
+				} else {
+					drrw->drr_compressiontype =
+					    ZIO_COMPRESS_OFF;
 				}
 				free(lzbuf);
 			} else {
diff --git a/man/man8/zstream.8 b/man/man8/zstream.8
index dd5342000..bfe7ac3f6 100644
--- a/man/man8/zstream.8
+++ b/man/man8/zstream.8
@@ -20,7 +20,7 @@
 .\"
 .\" Copyright (c) 2020 by Delphix. All rights reserved.
 .\"
-.Dd March 25, 2022
+.Dd October 4, 2022
 .Dt ZSTREAM 8
 .Os
 .
@@ -96,6 +96,7 @@ Specify the object number and byte offset of each record that you wish to
 decompress.
 Optionally specify the compression type.
 Valid compression types include
+.Sy off ,
 .Sy gzip ,
 .Sy lz4 ,
 .Sy lzjb ,
@@ -108,6 +109,11 @@ Every record for that object beginning at that offset will be decompressed, if
 possible.
 It may not be possible, because the record may be corrupted in some but not
 all of the stream's snapshots.
+Specifying a compression type of
+.Sy off
+will change the stream's metadata accordingly, without attempting decompression.
+This can be useful if the record is already uncompressed but the metadata
+insists otherwise.
 The repaired stream will be written to standard output.
 .Bl -tag -width "-v"
 .It Fl v