Re: [Qemu-devel] [PATCH 7/7] block/raw-posix: set max_write_zeroes to INT_MAX for regular files

[Max Reitz <mreitz@redhat.com>]

On 2015-01-28 at 13:38, Denis V. Lunev wrote:
> fallocate() works fine and could handle properly with arbitrary size
> requests. There is no sense to reduce the amount of space to fallocate.
> The bigger is the size, the better is the performance as the amount of
> journal updates is reduced.
>
> The patch changes behavior for both generic filesystem and XFS codepaths,
> which are different in handle_aiocb_write_zeroes. The implementation
> of falocate and xfsctl(XFS_IOC_ZERO_RANGE) for XFS are exactly the same

*fallocate

With that fixed:

Reviewed-by: Max Reitz <mreitz@redhat.com>

> thus the change is fine for both ways.
>
> Signed-off-by: Denis V. Lunev <den@openvz.org>
> CC: Max Reitz <mreitz@redhat.com>
> CC: Kevin Wolf <kwolf@redhat.com>
> CC: Stefan Hajnoczi <stefanha@redhat.com>
> CC: Peter Lieven <pl@kamp.de>
> CC: Fam Zheng <famz@redhat.com>
> ---
>   block/raw-posix.c | 17 +++++++++++++++++
>   1 file changed, 17 insertions(+)
>
> diff --git a/block/raw-posix.c b/block/raw-posix.c
> index 3db911a..ec38fee 100644
> --- a/block/raw-posix.c
> +++ b/block/raw-posix.c
> @@ -293,6 +293,20 @@ static void raw_probe_alignment(BlockDriverState *bs, int fd, Error **errp)
>       }
>   }
>   
> +static void raw_probe_max_write_zeroes(BlockDriverState *bs)
> +{
> +    BDRVRawState *s = bs->opaque;
> +    struct stat st;
> +
> +    if (fstat(s->fd, &st) < 0) {
> +        return; /* no problem, keep default value */
> +    }
> +    if (!S_ISREG(st.st_mode) || !s->discard_zeroes) {
> +        return;
> +    }
> +    bs->bl.max_write_zeroes = INT_MAX;
> +}
> +
>   static void raw_parse_flags(int bdrv_flags, int *open_flags)
>   {
>       assert(open_flags != NULL);
> @@ -600,6 +614,7 @@ static int raw_reopen_prepare(BDRVReopenState *state,
>       /* Fail already reopen_prepare() if we can't get a working O_DIRECT
>        * alignment with the new fd. */
>       if (raw_s->fd != -1) {
> +        raw_probe_max_write_zeroes(state->bs);
>           raw_probe_alignment(state->bs, raw_s->fd, &local_err);
>           if (local_err) {
>               qemu_close(raw_s->fd);
> @@ -653,6 +668,8 @@ static void raw_refresh_limits(BlockDriverState *bs, Error **errp)
>   
>       raw_probe_alignment(bs, s->fd, errp);
>       bs->bl.opt_mem_alignment = s->buf_align;
> +
> +    raw_probe_max_write_zeroes(bs);
>   }
>   
>   static ssize_t handle_aiocb_ioctl(RawPosixAIOData *aiocb)