Re: [Qemu-devel] [PATCH v8 3/4] raw-posix: Add full image preallocation option

[Eric Blake]

On 04/09/2014 01:12 AM, Hu Tao wrote:
> This patch adds a new option preallocation for raw format, and implements
> full preallocation.
> 
> Signed-off-by: Hu Tao <address@hidden>
> ---
>  block/raw-posix.c | 61 
> ++++++++++++++++++++++++++++++++++++++++++++++++-------
>  1 file changed, 54 insertions(+), 7 deletions(-)
> 

> +    if (prealloc == PREALLOC_MODE_METADATA) {
> +        /* posix_fallocate() doesn't set errno. */
> +        result = -posix_fallocate(fd, 0, total_size);
> +        if (result != 0) {
> +            error_setg_errno(errp, -result,
> +                             "Could not preallocate data for the new file");
>          }
> -        if (qemu_close(fd) != 0) {
> -            result = -errno;
> -            error_setg_errno(errp, -result, "Could not close the new file");
> +    } else if (prealloc == PREALLOC_MODE_FULL) {
> +        char *buf = g_malloc0(65536);
> +        int64_t num = 0, left = total_size;
> +
> +        while (left > 0) {
> +            num = MIN(left, 65536);
> +            result = write(fd, buf, num);
> +            if (result < 0) {
> +                result = -errno;
> +                error_setg_errno(errp, -result,
> +                                 "Could not write to the new file");
> +                g_free(buf);
> +                goto out_close;
> +            }
> +            left -= num;
>          }
> +        fsync(fd);
> +        g_free(buf);
> +    }
> +out_close:
> +    if (qemu_close(fd) != 0) {
> +        result = -errno;

This overwrites any earlier failure with the failure of close, which may
less informative.  I think you want to use 'if (!result) { result =
-errno; }' rather than blindly losing information.

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

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