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Re: [Qemu-block] [Qemu-devel] [PATCH v2] raw_bsd: add offset and size op
From: |
Daniel P. Berrange |
Subject: |
Re: [Qemu-block] [Qemu-devel] [PATCH v2] raw_bsd: add offset and size options |
Date: |
Tue, 18 Oct 2016 13:03:36 +0100 |
User-agent: |
Mutt/1.7.0 (2016-08-17) |
On Tue, Oct 18, 2016 at 12:25:17AM +0200, Tomáš Golembiovský wrote:
> Added two new options 'offset' and 'size'. This makes it possible to use
> only part of the file as a device. This can be used e.g. to limit the
> access only to single partition in a disk image or use a disk inside a
> tar archive (like OVA).
>
> When 'size' is specified we do our best to honour it.
>
> Signed-off-by: Tomáš Golembiovský <address@hidden>
> ---
> block/raw_bsd.c | 169
> ++++++++++++++++++++++++++++++++++++++++++++++++++-
> qapi/block-core.json | 16 ++++-
> 2 files changed, 181 insertions(+), 4 deletions(-)
>
> diff --git a/block/raw_bsd.c b/block/raw_bsd.c
> index 588d408..3fb3f13 100644
> --- a/block/raw_bsd.c
> +++ b/block/raw_bsd.c
> @@ -31,6 +31,30 @@
> #include "qapi/error.h"
> #include "qemu/option.h"
>
> +typedef struct BDRVRawState {
> + uint64_t offset;
> + uint64_t size;
> + bool has_size;
> +} BDRVRawState;
> +
> +static QemuOptsList raw_runtime_opts = {
> + .name = "raw",
> + .head = QTAILQ_HEAD_INITIALIZER(raw_runtime_opts.head),
> + .desc = {
> + {
> + .name = "offset",
> + .type = QEMU_OPT_SIZE,
> + .help = "offset in the disk where the image starts",
> + },
> + {
> + .name = "size",
> + .type = QEMU_OPT_SIZE,
> + .help = "virtual disk size",
> + },
> + { /* end of list */ }
> + },
> +};
> +
> static QemuOptsList raw_create_opts = {
> .name = "raw-create-opts",
> .head = QTAILQ_HEAD_INITIALIZER(raw_create_opts.head),
> @@ -44,17 +68,107 @@ static QemuOptsList raw_create_opts = {
> }
> };
>
> +static int raw_read_options(QDict *options, BlockDriverState *bs,
> + BDRVRawState *s, Error **errp)
> +{
> + Error *local_err = NULL;
> + QemuOpts *opts = NULL;
> + int64_t real_size = 0;
> + int ret;
> +
> + real_size = bdrv_getlength(bs->file->bs);
> + if (real_size < 0) {
> + error_setg_errno(errp, -real_size, "Could not get image size");
> + return real_size;
> + }
> +
> + opts = qemu_opts_create(&raw_runtime_opts, NULL, 0, &error_abort);
> + qemu_opts_absorb_qdict(opts, options, &local_err);
> + if (local_err) {
> + error_propagate(errp, local_err);
> + ret = -EINVAL;
> + goto fail;
> + }
> +
> + s->offset = qemu_opt_get_size(opts, "offset", 0);
> + if (qemu_opt_find(opts, "size") != NULL) {
> + s->size = qemu_opt_get_size(opts, "size", 0);
> + s->has_size = true;
> + } else {
> + s->has_size = false;
> + s->size = real_size;
> + }
> +
> + /* Check size and offset */
> + if (real_size < s->offset || (real_size - s->offset) < s->size) {
> + error_setg(errp, "The sum of offset (%"PRIu64") and size "
> + "(%"PRIu64") has to be smaller or equal to the "
> + " actual size of the containing file (%"PRId64").",
> + s->offset, s->size, real_size);
> + ret = -EINVAL;
> + goto fail;
> + }
> +
> + /* Make sure size is multiple of BDRV_SECTOR_SIZE to prevent rounding
> + * up and leaking out of the specified area. */
> + if (s->size != QEMU_ALIGN_DOWN(s->size, BDRV_SECTOR_SIZE)) {
> + s->size = QEMU_ALIGN_DOWN(s->size, BDRV_SECTOR_SIZE);
> + fprintf(stderr,
> + "WARNING: Specified size is not multiple of %llu! "
> + "Rounding down to %"PRIu64 ". (End of the image will be "
> + "ignored.)\n",
> + BDRV_SECTOR_SIZE, s->size);
IMHO you should be using error_setg here - I don't see a compelling
reason to let execution continue with incorrect values set.
Regards,
Daniel
--
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