On Mon, Aug 15, 2016 at 02:11:49PM +0200, Reda Sallahi wrote:
> dd was creating an output image regardless of whether there was one already
> created. With this patch we try to open first the output image and resize it
> if necessary.
>
> We also make it mandatory to specify conv=notrunc when the file already
> exists.
>
> Signed-off-by: Reda Sallahi <fullma...@gmail.com>
> ---
> Depends on:
> [PATCH v3] qemu-img: add conv=notrunc option to dd
>
> Changes from v2:
> * Remove redundant code
> Changes from v1:
> * add --image-opts handling
>
> qemu-img.c | 149
> ++++++++++++++++++++++++++++++++++++++++---------------------
> 1 file changed, 98 insertions(+), 51 deletions(-)
>
> diff --git a/qemu-img.c b/qemu-img.c
> index d08905b..8af6dd9 100644
> --- a/qemu-img.c
> +++ b/qemu-img.c
> @@ -3919,7 +3919,8 @@ static int img_dd(int argc, char **argv)
> char *tmp;
> BlockDriver *drv = NULL, *proto_drv = NULL;
> BlockBackend *blk1 = NULL, *blk2 = NULL;
> - QemuOpts *opts = NULL;
> + QDict *qoptions = NULL;
> + QemuOpts *opts = NULL, *qopts = NULL;
> QemuOptsList *create_opts = NULL;
> Error *local_err = NULL;
> bool image_opts = false;
> @@ -4030,36 +4031,6 @@ static int img_dd(int argc, char **argv)
> goto out;
> }
>
> - drv = bdrv_find_format(out_fmt);
> - if (!drv) {
> - error_report("Unknown file format");
> - ret = -1;
> - goto out;
> - }
> - proto_drv = bdrv_find_protocol(out.filename, true, &local_err);
> -
> - if (!proto_drv) {
> - error_report_err(local_err);
> - 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);
> -
> size = blk_getlength(blk1);
> if (size < 0) {
> error_report("Failed to get size for '%s'", in.filename);
> @@ -4071,31 +4042,106 @@ static int img_dd(int argc, char **argv)
> dd.count * in.bsz < size) {
> 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);
> + if (image_opts) {
> + qopts = qemu_opts_parse_noisily(qemu_find_opts("source"),
> + out.filename, true);
> + if (!opts) {
> + ret = -1;
> + goto out;
> + }
> + qoptions = qemu_opts_to_qdict(qopts, NULL);
> } else {
> - qemu_opt_set_number(opts, BLOCK_OPT_SIZE,
> - size - in.bsz * in.offset, &error_abort);
> + qoptions = qdict_new();
> + qdict_put(qoptions, "driver", qstring_from_str(out_fmt));
> }
>
> - 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;
> - }
> -
> - blk2 = img_open(image_opts, out.filename, out_fmt, BDRV_O_RDWR,
> - false, false);
> + blk2 = blk_new_open(image_opts ? NULL : out.filename,
> + NULL, qoptions, BDRV_O_RDWR, NULL);
This code duplicates a subset of img_open(). Why can't you use
img_open() or at least img_open_opts()/img_open_file()?
>
> if (!blk2) {
> - ret = -1;
> - goto out;
> + drv = bdrv_find_format(out_fmt);
> + if (!drv) {
> + error_report("Unknown file format");
> + ret = -1;
> + goto out;
> + }
> + proto_drv = bdrv_find_protocol(out.filename, true, &local_err);
> +
> + if (!proto_drv) {
> + error_report_err(local_err);
> + 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);
> +
> + /* Overflow means the specified offset is beyond input image's size
> */
> + if (dd.flags & C_SKIP && (in.offset > INT64_MAX / in.bsz ||
> + size < in.offset * in.bsz)) {
Please drop dd.flags & C_SKIP, it makes the expression more complicated
but doesn't add anything. We only need to look at in.offset.
> + qemu_opt_set_number(opts, BLOCK_OPT_SIZE,
> + 0, &error_abort);
> + } else {
> + qemu_opt_set_number(opts, BLOCK_OPT_SIZE,
> + size - in.offset * in.bsz, &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;
> + }
> + blk2 = img_open(image_opts, out.filename, out_fmt, BDRV_O_RDWR,
> + false, false);
> + if (!blk2) {
> + ret = -1;
> + goto out;
> + }
> + } else {
> + int64_t blk2sz = 0;
> +
> + if (!(dd.conv & C_NOTRUNC)) {
> + /* We make conv=notrunc mandatory for the moment to avoid
> + accidental destruction of the output image. Needs to be
> + changed when a better solution is found */
> + error_report("conv=notrunc not specified");
> + ret = -1;
> + goto out;
> + }
> +
> + blk2sz = blk_getlength(blk2);
> + if (blk2sz < 0) {
> + error_report("Failed to get size for '%s'", in.filename);
> + ret = -1;
> + goto out;
> + }
> +
> + if (!(dd.conv & C_NOTRUNC)) {
> + blk_truncate(blk2, 0);
> + }
This is dead code since the check above requires conv=notrunc.
(If it's dead code, it can't be tested and shouldn't be included.)
> + if (!(dd.flags & C_SKIP) || (in.offset <= INT64_MAX / in.bsz &&
> + size >= in.offset * in.bsz)) {
C_SKIP check isn't needed.
> + if (!(dd.conv & C_NOTRUNC) ||
> + blk2sz < size - in.offset * in.bsz) {
> + blk_truncate(blk2, size - in.offset * in.bsz);
> + }
It would be cleaner to calculate the output size upfront:
output_size = size - in.offset * in.bsz;
That way the calculation doesn't need to be duplicated several times in
the code.
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