Re: [PATCH 10/13] qemu-io: add -g to write past the end of the image

[Kevin Wolf <kwolf@redhat.com>]

Am 30.09.2026 um 18:49 hat Denis V. Lunev geschrieben:
> From: Denis V. Lunev <den@openvz.org>
> 
> The preallocate filter only does anything for a write that lands beyond
> the end of its file, and that is what a format driver above it produces.
> qemu-io could not produce it at all: the backend rejects such a request
> with EIO, and the write path asserts without the resize permission, so
> the filter could only be reached by stacking a real format on top and
> letting it choose the offsets.
> 
> Take the resize permission and allow writes beyond the end when -g is
> given, which leaves the tool free to address the filter directly.
> 
> Signed-off-by: Denis V. Lunev <den@openvz.org>
> CC: Kevin Wolf <kwolf@redhat.com>
> CC: Hanna Reitz <hreitz@redhat.com>
> CC: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
> CC: Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>

> @@ -310,6 +330,8 @@ static void usage(const char *name)
>  "                       specify tracing options\n"
>  "                       see qemu-img(1) man page for full description\n"
>  "  -U, --force-share    force shared permissions\n"
> +"  -g, --grow           let writes extend the image past its end,\n"
> +"                       as a format driver does to its file\n"
>  "  -h, --help           display this help and exit\n"
>  "  -V, --version        output version information and exit\n"
>  "\n"
> @@ -503,7 +525,7 @@ static QemuOptsList file_opts = {
>  int main(int argc, char **argv)
>  {
>      int readonly = 0;
> -    const char *sopt = "hVc:d:f:rsnCmki:t:T:U";
> +    const char *sopt = "hVc:d:f:grsnCmki:t:T:U";
>      const struct option lopt[] = {
>          { "help", no_argument, NULL, 'h' },
>          { "version", no_argument, NULL, 'V' },
> @@ -522,6 +544,7 @@ int main(int argc, char **argv)
>          { "object", required_argument, NULL, OPTION_OBJECT },
>          { "image-opts", no_argument, NULL, OPTION_IMAGE_OPTS },
>          { "force-share", no_argument, 0, 'U'},
> +        { "grow", no_argument, NULL, 'g' },
>          { NULL, 0, NULL, 0 }
>      };

--growable instead of just --grow would be more consistent with the
terminology we use elsewhere (e.g. block export interfaces).

Kevin