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

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
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(+)

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)