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Re: [Qemu-block] [PATCH 4/6] raw-posix: Switch to bdrv_co_* interfaces
From: |
Eric Blake |
Subject: |
Re: [Qemu-block] [PATCH 4/6] raw-posix: Switch to bdrv_co_* interfaces |
Date: |
Wed, 8 Jun 2016 09:13:35 -0600 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 |
On 06/08/2016 08:10 AM, Kevin Wolf wrote:
> In order to use the modern byte-based .bdrv_co_preadv/pwritev()
> interface, this patch switches raw-posix to coroutine-based interfaces
> as a first step. In terms of semantics and performance, it doesn't make
> a difference with the existing code whether we go from a coroutine to a
> callback-based interface already in block/io.c or only in linux-aio.c
>
> As there have been concerns in the past that this change may be a step
> in the wrong direction with respect to a possible AIO fast path, the
> old callback-based interface for linux-aio is left around and can be
> reactivated when a fast path (e.g. directly from virtio-blk dataplane,
> bypassing the whole block layer) is implemented.
>
> Signed-off-by: Kevin Wolf <address@hidden>
> ---
> block/linux-aio.c | 85
> +++++++++++++++++++++++++++++++++++++++++--------------
> block/raw-aio.h | 2 ++
> block/raw-posix.c | 59 ++++++++++++++++++--------------------
> 3 files changed, 92 insertions(+), 54 deletions(-)
>
> +
> +int laio_submit_co(BlockDriverState *bs, LinuxAioState *s, int fd,
> + int64_t sector_num, QEMUIOVector *qiov, int nb_sectors, int type)
> +{
> + off_t offset = sector_num * 512;
BDRV_SECTOR_SIZE instead of a magic number?
> + int ret;
> +
> + struct qemu_laiocb laiocb = {
> + .co = qemu_coroutine_self(),
> + .nbytes = nb_sectors * 512,
and again
> +
> +BlockAIOCB *laio_submit(BlockDriverState *bs, LinuxAioState *s, int fd,
> + int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
> + BlockCompletionFunc *cb, void *opaque, int type)
> +{
> + struct qemu_laiocb *laiocb;
> + off_t offset = sector_num * 512;
> + int ret;
> +
> + laiocb = qemu_aio_get(&laio_aiocb_info, bs, cb, opaque);
> + laiocb->nbytes = nb_sectors * 512;
and again
> @@ -1345,14 +1344,26 @@ static BlockAIOCB *raw_aio_submit(BlockDriverState
> *bs,
> type |= QEMU_AIO_MISALIGNED;
> #ifdef CONFIG_LINUX_AIO
> } else if (s->use_aio) {
> - return laio_submit(bs, s->aio_ctx, s->fd, sector_num, qiov,
> - nb_sectors, cb, opaque, type);
> + return laio_submit_co(bs, s->aio_ctx, s->fd, sector_num, qiov,
> + nb_sectors, type);
Indentation is now off
> @@ -1957,8 +1952,8 @@ BlockDriver bdrv_file = {
> .bdrv_co_get_block_status = raw_co_get_block_status,
> .bdrv_co_pwrite_zeroes = raw_co_pwrite_zeroes,
>
> - .bdrv_aio_readv = raw_aio_readv,
> - .bdrv_aio_writev = raw_aio_writev,
> + .bdrv_co_readv = raw_co_readv,
> + .bdrv_co_writev = raw_co_writev,
> .bdrv_aio_flush = raw_aio_flush,
Why bother with indented alignment of '=' when none of the neighbors do?
Findings are minor enough, so up to you whether to fix them or just mark
this:
Reviewed-by: Eric Blake <address@hidden>
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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- [Qemu-block] [PATCH 1/6] block: Byte-based bdrv_co_do_copy_on_readv(), (continued)
- [Qemu-block] [PATCH 1/6] block: Byte-based bdrv_co_do_copy_on_readv(), Kevin Wolf, 2016/06/08
- [Qemu-block] [PATCH 5/6] raw-posix: Implement .bdrv_co_preadv/pwritev, Kevin Wolf, 2016/06/08
- [Qemu-block] [PATCH 3/6] block: Prepare bdrv_aligned_pwritev() for byte-aligned requests, Kevin Wolf, 2016/06/08
- [Qemu-block] [PATCH 4/6] raw-posix: Switch to bdrv_co_* interfaces, Kevin Wolf, 2016/06/08
- [Qemu-block] [PATCH 6/6] block: Don't enforce 512 byte minimum alignment, Kevin Wolf, 2016/06/08
- Re: [Qemu-block] [PATCH 0/6] block: Enable byte granularity I/O, Stefan Hajnoczi, 2016/06/13