On Tue, May 23, 2023 at 01:12:59PM -0400, Stefan Hajnoczi wrote:
> Stop using the .bdrv_co_io_plug() API because it is not multi-queue
> block layer friendly. Use the new blk_io_plug_call() API to batch I/O
> submission instead.
>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> Reviewed-by: Eric Blake <eblake@redhat.com>
> ---
> include/block/raw-aio.h | 7 -------
> block/file-posix.c | 28 ----------------------------
> block/linux-aio.c | 41 +++++++++++------------------------------
> 3 files changed, 11 insertions(+), 65 deletions(-)
>
> diff --git a/include/block/raw-aio.h b/include/block/raw-aio.h
> index da60ca13ef..0f63c2800c 100644
> --- a/include/block/raw-aio.h
> +++ b/include/block/raw-aio.h
> @@ -62,13 +62,6 @@ int coroutine_fn laio_co_submit(int fd, uint64_t offset,
QEMUIOVector *qiov,
>
> void laio_detach_aio_context(LinuxAioState *s, AioContext *old_context);
> void laio_attach_aio_context(LinuxAioState *s, AioContext *new_context);
> -
> -/*
> - * laio_io_plug/unplug work in the thread's current AioContext, therefore the
> - * caller must ensure that they are paired in the same IOThread.
> - */
> -void laio_io_plug(void);
> -void laio_io_unplug(uint64_t dev_max_batch);
> #endif
> /* io_uring.c - Linux io_uring implementation */
> #ifdef CONFIG_LINUX_IO_URING
> diff --git a/block/file-posix.c b/block/file-posix.c
> index 7baa8491dd..ac1ed54811 100644
> --- a/block/file-posix.c
> +++ b/block/file-posix.c
> @@ -2550,26 +2550,6 @@ static int coroutine_fn
raw_co_pwritev(BlockDriverState *bs, int64_t offset,
> return raw_co_prw(bs, offset, bytes, qiov, QEMU_AIO_WRITE);
> }
>
> -static void coroutine_fn raw_co_io_plug(BlockDriverState *bs)
> -{
> - BDRVRawState __attribute__((unused)) *s = bs->opaque;
> -#ifdef CONFIG_LINUX_AIO
> - if (s->use_linux_aio) {
> - laio_io_plug();
> - }
> -#endif
> -}
> -
> -static void coroutine_fn raw_co_io_unplug(BlockDriverState *bs)
> -{
> - BDRVRawState __attribute__((unused)) *s = bs->opaque;
> -#ifdef CONFIG_LINUX_AIO
> - if (s->use_linux_aio) {
> - laio_io_unplug(s->aio_max_batch);
> - }
> -#endif
> -}
> -
> static int coroutine_fn raw_co_flush_to_disk(BlockDriverState *bs)
> {
> BDRVRawState *s = bs->opaque;
> @@ -3914,8 +3894,6 @@ BlockDriver bdrv_file = {
> .bdrv_co_copy_range_from = raw_co_copy_range_from,
> .bdrv_co_copy_range_to = raw_co_copy_range_to,
> .bdrv_refresh_limits = raw_refresh_limits,
> - .bdrv_co_io_plug = raw_co_io_plug,
> - .bdrv_co_io_unplug = raw_co_io_unplug,
> .bdrv_attach_aio_context = raw_aio_attach_aio_context,
>
> .bdrv_co_truncate = raw_co_truncate,
> @@ -4286,8 +4264,6 @@ static BlockDriver bdrv_host_device = {
> .bdrv_co_copy_range_from = raw_co_copy_range_from,
> .bdrv_co_copy_range_to = raw_co_copy_range_to,
> .bdrv_refresh_limits = raw_refresh_limits,
> - .bdrv_co_io_plug = raw_co_io_plug,
> - .bdrv_co_io_unplug = raw_co_io_unplug,
> .bdrv_attach_aio_context = raw_aio_attach_aio_context,
>
> .bdrv_co_truncate = raw_co_truncate,
> @@ -4424,8 +4400,6 @@ static BlockDriver bdrv_host_cdrom = {
> .bdrv_co_pwritev = raw_co_pwritev,
> .bdrv_co_flush_to_disk = raw_co_flush_to_disk,
> .bdrv_refresh_limits = cdrom_refresh_limits,
> - .bdrv_co_io_plug = raw_co_io_plug,
> - .bdrv_co_io_unplug = raw_co_io_unplug,
> .bdrv_attach_aio_context = raw_aio_attach_aio_context,
>
> .bdrv_co_truncate = raw_co_truncate,
> @@ -4552,8 +4526,6 @@ static BlockDriver bdrv_host_cdrom = {
> .bdrv_co_pwritev = raw_co_pwritev,
> .bdrv_co_flush_to_disk = raw_co_flush_to_disk,
> .bdrv_refresh_limits = cdrom_refresh_limits,
> - .bdrv_co_io_plug = raw_co_io_plug,
> - .bdrv_co_io_unplug = raw_co_io_unplug,
> .bdrv_attach_aio_context = raw_aio_attach_aio_context,
>
> .bdrv_co_truncate = raw_co_truncate,
> diff --git a/block/linux-aio.c b/block/linux-aio.c
> index 442c86209b..5021aed68f 100644
> --- a/block/linux-aio.c
> +++ b/block/linux-aio.c
> @@ -15,6 +15,7 @@
> #include "qemu/event_notifier.h"
> #include "qemu/coroutine.h"
> #include "qapi/error.h"
> +#include "sysemu/block-backend.h"
>
> /* Only used for assertions. */
> #include "qemu/coroutine_int.h"
> @@ -46,7 +47,6 @@ struct qemu_laiocb {
> };
>
> typedef struct {
> - int plugged;
> unsigned int in_queue;
> unsigned int in_flight;
> bool blocked;
> @@ -236,7 +236,7 @@ static void
qemu_laio_process_completions_and_submit(LinuxAioState *s)
> {
> qemu_laio_process_completions(s);
>
> - if (!s->io_q.plugged && !QSIMPLEQ_EMPTY(&s->io_q.pending)) {
> + if (!QSIMPLEQ_EMPTY(&s->io_q.pending)) {
> ioq_submit(s);
> }
> }
> @@ -277,7 +277,6 @@ static void qemu_laio_poll_ready(EventNotifier *opaque)
> static void ioq_init(LaioQueue *io_q)
> {
> QSIMPLEQ_INIT(&io_q->pending);
> - io_q->plugged = 0;
> io_q->in_queue = 0;
> io_q->in_flight = 0;
> io_q->blocked = false;
> @@ -354,31 +353,11 @@ static uint64_t laio_max_batch(LinuxAioState *s,
uint64_t dev_max_batch)
> return max_batch;
> }
>
> -void laio_io_plug(void)
> +static void laio_unplug_fn(void *opaque)
> {
> - AioContext *ctx = qemu_get_current_aio_context();
> - LinuxAioState *s = aio_get_linux_aio(ctx);
> + LinuxAioState *s = opaque;
>
> - s->io_q.plugged++;
> -}
> -
> -void laio_io_unplug(uint64_t dev_max_batch)
> -{
> - AioContext *ctx = qemu_get_current_aio_context();
> - LinuxAioState *s = aio_get_linux_aio(ctx);
> -
> - assert(s->io_q.plugged);
> - s->io_q.plugged--;
> -
> - /*
> - * Why max batch checking is performed here:
> - * Another BDS may have queued requests with a higher dev_max_batch and
> - * therefore in_queue could now exceed our dev_max_batch. Re-check the
max
> - * batch so we can honor our device's dev_max_batch.
> - */
> - if (s->io_q.in_queue >= laio_max_batch(s, dev_max_batch) ||
Why are we removing this condition?
Could the same situation occur with the new API?