Re: [PATCH 3/6] block/blkio: convert to blk_io_plug_call() API

[Stefano Garzarella]

On Wed, May 17, 2023 at 06:10:19PM -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>
> ---
> block/blkio.c | 40 +++++++++++++++++++++-------------------
> 1 file changed, 21 insertions(+), 19 deletions(-)

With this patch, the build fails in several places, maybe it's an old
version:

../block/blkio.c:347:5: error: implicit declaration of function 
‘blk_io_plug_call’ [-Werror=implicit-function-declaration]
  347 |     blk_io_plug_call(blkio_unplug_fn, bs);

../block/blkio.c:348:22: error: passing argument 1 of ‘blk_io_plug_call’ 
from incompatible pointer type [-Werror=incompatible-pointer-types]
  348 |     blk_io_plug_call(blkio_unplug_fn, bs);

Thanks,
Stefano

> diff --git a/block/blkio.c b/block/blkio.c
> index 0cdc99a729..f2a1dc1fb2 100644
> --- a/block/blkio.c
> +++ b/block/blkio.c
> @@ -325,16 +325,28 @@ static void blkio_detach_aio_context(BlockDriverState *bs)
>                        false, NULL, NULL, NULL, NULL, NULL);
> }
>
> -/* Call with s->blkio_lock held to submit I/O after enqueuing a new request */
> -static void blkio_submit_io(BlockDriverState *bs)
> +/*
> + * Called by blk_io_unplug() or immediately if not plugged. Called without
> + * blkio_lock.
> + */
> +static void blkio_unplug_fn(BlockDriverState *bs)
> {
> -    if (qatomic_read(&bs->io_plugged) == 0) {
> -        BDRVBlkioState *s = bs->opaque;
> +    BDRVBlkioState *s = bs->opaque;
>
> +    WITH_QEMU_LOCK_GUARD(&s->blkio_lock) {
>         blkioq_do_io(s->blkioq, NULL, 0, 0, NULL);
>     }
> }
>
> +/*
> + * Schedule I/O submission after enqueuing a new request. Called without
> + * blkio_lock.
> + */
> +static void blkio_submit_io(BlockDriverState *bs)
> +{
> +    blk_io_plug_call(blkio_unplug_fn, bs);
> +}
> +
> static int coroutine_fn
> blkio_co_pdiscard(BlockDriverState *bs, int64_t offset, int64_t bytes)
> {
> @@ -345,9 +357,9 @@ blkio_co_pdiscard(BlockDriverState *bs, int64_t offset, 
> int64_t bytes)
>
>     WITH_QEMU_LOCK_GUARD(&s->blkio_lock) {
>         blkioq_discard(s->blkioq, offset, bytes, &cod, 0);
> -        blkio_submit_io(bs);
>     }
>
> +    blkio_submit_io(bs);
>     qemu_coroutine_yield();
>     return cod.ret;
> }
> @@ -378,9 +390,9 @@ blkio_co_preadv(BlockDriverState *bs, int64_t offset, 
> int64_t bytes,
>
>     WITH_QEMU_LOCK_GUARD(&s->blkio_lock) {
>         blkioq_readv(s->blkioq, offset, iov, iovcnt, &cod, 0);
> -        blkio_submit_io(bs);
>     }
>
> +    blkio_submit_io(bs);
>     qemu_coroutine_yield();
>
>     if (use_bounce_buffer) {
> @@ -423,9 +435,9 @@ static int coroutine_fn blkio_co_pwritev(BlockDriverState 
> *bs, int64_t offset,
>
>     WITH_QEMU_LOCK_GUARD(&s->blkio_lock) {
>         blkioq_writev(s->blkioq, offset, iov, iovcnt, &cod, blkio_flags);
> -        blkio_submit_io(bs);
>     }
>
> +    blkio_submit_io(bs);
>     qemu_coroutine_yield();
>
>     if (use_bounce_buffer) {
> @@ -444,9 +456,9 @@ static int coroutine_fn blkio_co_flush(BlockDriverState *bs)
>
>     WITH_QEMU_LOCK_GUARD(&s->blkio_lock) {
>         blkioq_flush(s->blkioq, &cod, 0);
> -        blkio_submit_io(bs);
>     }
>
> +    blkio_submit_io(bs);
>     qemu_coroutine_yield();
>     return cod.ret;
> }
> @@ -472,22 +484,13 @@ static int coroutine_fn 
> blkio_co_pwrite_zeroes(BlockDriverState *bs,
>
>     WITH_QEMU_LOCK_GUARD(&s->blkio_lock) {
>         blkioq_write_zeroes(s->blkioq, offset, bytes, &cod, blkio_flags);
> -        blkio_submit_io(bs);
>     }
>
> +    blkio_submit_io(bs);
>     qemu_coroutine_yield();
>     return cod.ret;
> }
>
> -static void coroutine_fn blkio_co_io_unplug(BlockDriverState *bs)
> -{
> -    BDRVBlkioState *s = bs->opaque;
> -
> -    WITH_QEMU_LOCK_GUARD(&s->blkio_lock) {
> -        blkio_submit_io(bs);
> -    }
> -}
> -
> typedef enum {
>     BMRR_OK,
>     BMRR_SKIP,
> @@ -1009,7 +1012,6 @@ static void blkio_refresh_limits(BlockDriverState *bs, 
> Error **errp)
>         .bdrv_co_pwritev         = blkio_co_pwritev, \
>         .bdrv_co_flush_to_disk   = blkio_co_flush, \
>         .bdrv_co_pwrite_zeroes   = blkio_co_pwrite_zeroes, \
> -        .bdrv_co_io_unplug       = blkio_co_io_unplug, \
>         .bdrv_refresh_limits     = blkio_refresh_limits, \
>         .bdrv_register_buf       = blkio_register_buf, \
>         .bdrv_unregister_buf     = blkio_unregister_buf, \
> --
> 2.40.1