Re: [Qemu-devel] [PATCH V9 3/4] raw-posix: Add full image preallocation option

[Eric Blake]

On 05/27/2014 02:22 AM, Chen Fan wrote:
> From: Hu Tao <address@hidden>
> 
> This patch adds a new option preallocation for raw format, and implements
> full preallocation by writing zeros to disk.
> 
> The metadata option is changed to use posix_fallocate() to ensure
> subsquent writes to image file won't fail because of lack of disk space.
> 
> The purpose is to ensure disk space for image file. In cases
> posix_fallocate() is supported, metadata option can be used, otherwise
> (posix_fallocate() is not supported by filesystem, or in case of thin
>  provisioning), full option has to be used. User has to choose the proper
> way to use.
> 
> Signed-off-by: Hu Tao <address@hidden>
> ---
>  block/raw-posix.c | 61 
> ++++++++++++++++++++++++++++++++++++++++++++++++-------
>  1 file changed, 54 insertions(+), 7 deletions(-)
> 

> @@ -1254,6 +1255,18 @@ static int raw_create(const char *filename, 
> QEMUOptionParameter *options,
>          if (!strcmp(options->name, BLOCK_OPT_SIZE)) {
>              total_size = (options->value.n + BDRV_SECTOR_SIZE) &
>                  BDRV_SECTOR_MASK;
> +        } else if (!strcmp(options->name, BLOCK_OPT_PREALLOC)) {
> +            if (!options->value.s || !strcmp(options->value.s, "off")) {
> +                prealloc = PREALLOC_MODE_OFF;
> +            } else if (!strcmp(options->value.s, "metadata")) {
> +                prealloc = PREALLOC_MODE_METADATA;
> +            } else if (!strcmp(options->value.s, "full")) {
> +                prealloc = PREALLOC_MODE_FULL;
> +            } else {

Instead of open-coding this conversion from string to enum, can you
reuse Peter's pending patch?  (Hmm, that means Peter needs to export it
to somewhere public, not just blockdev.c)

https://lists.gnu.org/archive/html/qemu-devel/2014-05/msg03772.html

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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