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[2001:8b0:bb71:7140:64::1]) by smtp.gmail.com with ESMTPSA id k6sm9193085ejb.84.2021.02.02.02.20.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 02 Feb 2021 02:20:22 -0800 (PST) Received: from localhost (disaster-area.hh.sledj.net [local]) by disaster-area.hh.sledj.net (OpenSMTPD) with ESMTPA id edab9290; Tue, 2 Feb 2021 10:20:21 +0000 (UTC) To: Peter Lieven , qemu-block@nongnu.org Subject: Re: [PATCH] qemu-img: add seek and -n option to dd command In-Reply-To: <20210128140704.6547-1-pl@kamp.de> References: <20210128140704.6547-1-pl@kamp.de> X-HGTTG: zarquon From: David Edmondson X-Now-Playing: Peter Gabriel - Up: The Barry Williams Show Date: Tue, 02 Feb 2021 10:20:21 +0000 Message-ID: MIME-Version: 1.0 Content-Type: text/plain Received-SPF: neutral client-ip=2a00:1450:4864:20::52c; envelope-from=dme@dme.org; helo=mail-ed1-x52c.google.com X-Spam_score_int: -10 X-Spam_score: -1.1 X-Spam_bar: - X-Spam_report: (-1.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_NEUTRAL=0.779, UNPARSEABLE_RELAY=0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kwolf@redhat.com, Peter Lieven , qemu-devel@nongnu.org, mreitz@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thursday, 2021-01-28 at 15:07:04 +01, Peter Lieven wrote: > Signed-off-by: Peter Lieven > > diff --git a/docs/tools/qemu-img.rst b/docs/tools/qemu-img.rst > index b615aa8419..7d4564c2b8 100644 > --- a/docs/tools/qemu-img.rst > +++ b/docs/tools/qemu-img.rst > @@ -209,6 +209,10 @@ Parameters to dd subcommand: > > .. program:: qemu-img-dd > > +.. option:: -n > + > + Skip the creation of the output file > + > .. option:: bs=BLOCK_SIZE > > Defines the block size > @@ -229,6 +233,10 @@ Parameters to dd subcommand: > > Sets the number of input blocks to skip > > +.. option:: sseek=BLOCKS > + > + Sets the number of blocks to seek into the output > + > Parameters to snapshot subcommand: > > .. program:: qemu-img-snapshot > diff --git a/qemu-img.c b/qemu-img.c > index 8597d069af..d7f390e382 100644 > --- a/qemu-img.c > +++ b/qemu-img.c > @@ -213,12 +213,17 @@ static void QEMU_NORETURN help(void) > " '-s' run in Strict mode - fail on different image size or sector allocation\n" > "\n" > "Parameters to dd subcommand:\n" > + " '-n' skips the target volume creation (useful if the volume is created\n" > + " prior to running qemu-img). Note that he behaviour is not identical to\n" s/he/the/ > + " original dd option conv=nocreat. The output is neither truncated nor\n" > + " is it possible to write past the end of an existing file.\n" > " 'bs=BYTES' read and write up to BYTES bytes at a time " > "(default: 512)\n" > " 'count=N' copy only N input blocks\n" > " 'if=FILE' read from FILE\n" > " 'of=FILE' write to FILE\n" > - " 'skip=N' skip N bs-sized blocks at the start of input\n"; > + " 'skip=N' skip N bs-sized blocks at the start of input\n" > + " 'seek=N' seek N bs-sized blocks into the output\n"; > > printf("%s\nSupported formats:", help_msg); > bdrv_iterate_format(format_print, NULL, false); > @@ -4885,6 +4890,7 @@ static int img_bitmap(int argc, char **argv) > #define C_IF 04 > #define C_OF 010 > #define C_SKIP 020 > +#define C_SEEK 040 > > struct DdInfo { > unsigned int flags; > @@ -4964,6 +4970,19 @@ static int img_dd_skip(const char *arg, > return 0; > } > > +static int img_dd_seek(const char *arg, > + struct DdIo *in, struct DdIo *out, > + struct DdInfo *dd) > +{ > + out->offset = cvtnum("seek", arg); > + > + if (in->offset < 0) { > + return 1; > + } > + > + return 0; > +} > + > static int img_dd(int argc, char **argv) > { > int ret = 0; > @@ -4980,7 +4999,7 @@ static int img_dd(int argc, char **argv) > const char *fmt = NULL; > int64_t size = 0; > int64_t block_count = 0, out_pos, in_pos; > - bool force_share = false; > + bool force_share = false, skip_create = false; > struct DdInfo dd = { > .flags = 0, > .count = 0, > @@ -5004,6 +5023,7 @@ static int img_dd(int argc, char **argv) > { "if", img_dd_if, C_IF }, > { "of", img_dd_of, C_OF }, > { "skip", img_dd_skip, C_SKIP }, > + { "seek", img_dd_seek, C_SEEK }, > { NULL, NULL, 0 } > }; > const struct option long_options[] = { > @@ -5014,7 +5034,7 @@ static int img_dd(int argc, char **argv) > { 0, 0, 0, 0 } > }; > > - while ((c = getopt_long(argc, argv, ":hf:O:U", long_options, NULL))) { > + while ((c = getopt_long(argc, argv, ":hf:O:Un", long_options, NULL))) { > if (c == EOF) { > break; > } > @@ -5037,6 +5057,9 @@ static int img_dd(int argc, char **argv) > case 'U': > force_share = true; > break; > + case 'n': > + skip_create = true; > + break; > case OPTION_OBJECT: > if (!qemu_opts_parse_noisily(&qemu_object_opts, optarg, true)) { > ret = -1; > @@ -5116,22 +5139,25 @@ static int img_dd(int argc, char **argv) > ret = -1; > goto out; > } > - if (!drv->create_opts) { > - error_report("Format driver '%s' does not support image creation", > - drv->format_name); > - ret = -1; > - goto out; > - } > - if (!proto_drv->create_opts) { > - error_report("Protocol driver '%s' does not support image creation", > - proto_drv->format_name); > - ret = -1; > - goto out; > - } > - create_opts = qemu_opts_append(create_opts, drv->create_opts); > - create_opts = qemu_opts_append(create_opts, proto_drv->create_opts); > > - opts = qemu_opts_create(create_opts, NULL, 0, &error_abort); > + if (!skip_create) { > + if (!drv->create_opts) { > + error_report("Format driver '%s' does not support image creation", > + drv->format_name); > + ret = -1; > + goto out; > + } > + if (!proto_drv->create_opts) { > + error_report("Protocol driver '%s' does not support image creation", > + proto_drv->format_name); > + ret = -1; > + goto out; > + } > + create_opts = qemu_opts_append(create_opts, drv->create_opts); > + create_opts = qemu_opts_append(create_opts, proto_drv->create_opts); > + > + opts = qemu_opts_create(create_opts, NULL, 0, &error_abort); > + } > > size = blk_getlength(blk1); > if (size < 0) { > @@ -5145,22 +5171,25 @@ static int img_dd(int argc, char **argv) > size = dd.count * in.bsz; > } > > - /* Overflow means the specified offset is beyond input image's size */ > - if (dd.flags & C_SKIP && (in.offset > INT64_MAX / in.bsz || > - size < in.bsz * in.offset)) { > - qemu_opt_set_number(opts, BLOCK_OPT_SIZE, 0, &error_abort); > - } else { > - qemu_opt_set_number(opts, BLOCK_OPT_SIZE, > - size - in.bsz * in.offset, &error_abort); > - } > + if (!skip_create) { > + /* Overflow means the specified offset is beyond input image's size */ > + if (dd.flags & C_SKIP && (in.offset > INT64_MAX / in.bsz || > + size < in.bsz * in.offset)) { > + qemu_opt_set_number(opts, BLOCK_OPT_SIZE, 0, &error_abort); > + } else { > + qemu_opt_set_number(opts, BLOCK_OPT_SIZE, > + out.bsz * out.offset + size - > + in.bsz * in.offset, &error_abort); > + } > > - ret = bdrv_create(drv, out.filename, opts, &local_err); > - if (ret < 0) { > - error_reportf_err(local_err, > - "%s: error while creating output image: ", > - out.filename); > - ret = -1; > - goto out; > + ret = bdrv_create(drv, out.filename, opts, &local_err); > + if (ret < 0) { > + error_reportf_err(local_err, > + "%s: error while creating output image: ", > + out.filename); > + ret = -1; > + goto out; > + } > } > > /* TODO, we can't honour --image-opts for the target, > @@ -5189,7 +5218,7 @@ static int img_dd(int argc, char **argv) > > in.buf = g_new(uint8_t, in.bsz); > > - for (out_pos = 0; in_pos < size; block_count++) { > + for (out_pos = out.offset * out.bsz; in_pos < size; block_count++) { > int in_ret, out_ret; > > if (in_pos + in.bsz > size) { > -- > 2.17.1 dme. -- But they'll laugh at you in Jackson, and I'll be dancin' on a Pony Keg.