Re: [PATCH 1/6] block: add blk_io_plug_call() API
On Tue, May 23, 2023 at 11:47:08AM -0400, Stefan Hajnoczi wrote:
On Fri, May 19, 2023 at 10:45:57AM +0200, Stefano Garzarella wrote:
On Wed, May 17, 2023 at 06:10:17PM -0400, Stefan Hajnoczi wrote:
> Introduce a new API for thread-local blk_io_plug() that does not
> traverse the block graph. The goal is to make blk_io_plug() multi-queue
> friendly.
>
> Instead of having block drivers track whether or not we're in a plugged
> section, provide an API that allows them to defer a function call until
> we're unplugged: blk_io_plug_call(fn, opaque). If blk_io_plug_call() is
> called multiple times with the same fn/opaque pair, then fn() is only
> called once at the end of the function - resulting in batching.
>
> This patch introduces the API and changes blk_io_plug()/blk_io_unplug().
> blk_io_plug()/blk_io_unplug() no longer require a BlockBackend argument
> because the plug state is now thread-local.
>
> Later patches convert block drivers to blk_io_plug_call() and then we
> can finally remove .bdrv_co_io_plug() once all block drivers have been
> converted.
>
> Signed-off-by: Stefan Hajnoczi
> ---
> MAINTAINERS | 1 +
> include/sysemu/block-backend-io.h | 13 +--
> block/block-backend.c | 22 -
> block/plug.c | 159 ++
> hw/block/dataplane/xen-block.c| 8 +-
> hw/block/virtio-blk.c | 4 +-
> hw/scsi/virtio-scsi.c | 6 +-
> block/meson.build | 1 +
> 8 files changed, 173 insertions(+), 41 deletions(-)
> create mode 100644 block/plug.c
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 50585117a0..574202295c 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -2644,6 +2644,7 @@ F: util/aio-*.c
> F: util/aio-*.h
> F: util/fdmon-*.c
> F: block/io.c
> +F: block/plug.c
> F: migration/block*
> F: include/block/aio.h
> F: include/block/aio-wait.h
> diff --git a/include/sysemu/block-backend-io.h
b/include/sysemu/block-backend-io.h
> index d62a7ee773..be4dcef59d 100644
> --- a/include/sysemu/block-backend-io.h
> +++ b/include/sysemu/block-backend-io.h
> @@ -100,16 +100,9 @@ void blk_iostatus_set_err(BlockBackend *blk, int error);
> int blk_get_max_iov(BlockBackend *blk);
> int blk_get_max_hw_iov(BlockBackend *blk);
>
> -/*
> - * blk_io_plug/unplug are thread-local operations. This means that multiple
> - * IOThreads can simultaneously call plug/unplug, but the caller must ensure
> - * that each unplug() is called in the same IOThread of the matching plug().
> - */
> -void coroutine_fn blk_co_io_plug(BlockBackend *blk);
> -void co_wrapper blk_io_plug(BlockBackend *blk);
> -
> -void coroutine_fn blk_co_io_unplug(BlockBackend *blk);
> -void co_wrapper blk_io_unplug(BlockBackend *blk);
> +void blk_io_plug(void);
> +void blk_io_unplug(void);
> +void blk_io_plug_call(void (*fn)(void *), void *opaque);
>
> AioContext *blk_get_aio_context(BlockBackend *blk);
> BlockAcctStats *blk_get_stats(BlockBackend *blk);
> diff --git a/block/block-backend.c b/block/block-backend.c
> index ca537cd0ad..1f1d226ba6 100644
> --- a/block/block-backend.c
> +++ b/block/block-backend.c
> @@ -2568,28 +2568,6 @@ void blk_add_insert_bs_notifier(BlockBackend *blk,
Notifier *notify)
> notifier_list_add(>insert_bs_notifiers, notify);
> }
>
> -void coroutine_fn blk_co_io_plug(BlockBackend *blk)
> -{
> -BlockDriverState *bs = blk_bs(blk);
> -IO_CODE();
> -GRAPH_RDLOCK_GUARD();
> -
> -if (bs) {
> -bdrv_co_io_plug(bs);
> -}
> -}
> -
> -void coroutine_fn blk_co_io_unplug(BlockBackend *blk)
> -{
> -BlockDriverState *bs = blk_bs(blk);
> -IO_CODE();
> -GRAPH_RDLOCK_GUARD();
> -
> -if (bs) {
> -bdrv_co_io_unplug(bs);
> -}
> -}
> -
> BlockAcctStats *blk_get_stats(BlockBackend *blk)
> {
> IO_CODE();
> diff --git a/block/plug.c b/block/plug.c
> new file mode 100644
> index 00..6738a568ba
> --- /dev/null
> +++ b/block/plug.c
> @@ -0,0 +1,159 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +/*
> + * Block I/O plugging
> + *
> + * Copyright Red Hat.
> + *
> + * This API defers a function call within a blk_io_plug()/blk_io_unplug()
> + * section, allowing multiple calls to batch up. This is a performance
> + * optimization that is used in the block layer to submit several I/O
requests
> + * at once instead of individually:
> + *
> + * blk_io_plug(); <-- start of plugged region
> + * ...
> + * blk_io_plug_call(my_func, my_obj); <-- deferred my_func(my_obj) call
> + * blk_io_plug_call(my_func, my_obj); <-- another
> + * blk_io_plug_call(my_func, my_obj); <-- another
> + * ...
> + * blk_io_unplug(); <-- end of plugged region, my_func(my_obj) is called
once
> + *
> + * This code is actually generic and not tied to the block layer. If another
> + * subsystem needs this functionality, it could be renamed.
> + */
> +
> +#include "qemu/osdep.h"
> +#include "qemu/coroutine-tls.h"
> +#include "qemu/notify.h"
> +#include "qemu/thread.h"
>
Re: [PATCH 1/6] block: add blk_io_plug_call() API
On Thu, May 18, 2023 at 07:04:52PM -0500, Eric Blake wrote: > On Wed, May 17, 2023 at 06:10:17PM -0400, Stefan Hajnoczi wrote: > > Introduce a new API for thread-local blk_io_plug() that does not > > traverse the block graph. The goal is to make blk_io_plug() multi-queue > > friendly. > > > > Instead of having block drivers track whether or not we're in a plugged > > section, provide an API that allows them to defer a function call until > > we're unplugged: blk_io_plug_call(fn, opaque). If blk_io_plug_call() is > > called multiple times with the same fn/opaque pair, then fn() is only > > called once at the end of the function - resulting in batching. > > > > This patch introduces the API and changes blk_io_plug()/blk_io_unplug(). > > blk_io_plug()/blk_io_unplug() no longer require a BlockBackend argument > > because the plug state is now thread-local. > > > > Later patches convert block drivers to blk_io_plug_call() and then we > > can finally remove .bdrv_co_io_plug() once all block drivers have been > > converted. > > > > Signed-off-by: Stefan Hajnoczi > > --- > > > +++ b/block/plug.c > > + > > +/** > > + * blk_io_plug_call: > > + * @fn: a function pointer to be invoked > > + * @opaque: a user-defined argument to @fn() > > + * > > + * Call @fn(@opaque) immediately if not within a > > blk_io_plug()/blk_io_unplug() > > + * section. > > + * > > + * Otherwise defer the call until the end of the outermost > > + * blk_io_plug()/blk_io_unplug() section in this thread. If the same > > + * @fn/@opaque pair has already been deferred, it will only be called once > > upon > > + * blk_io_unplug() so that accumulated calls are batched into a single > > call. > > + * > > + * The caller must ensure that @opaque is not be freed before @fn() is > > invoked. > > s/be // Will fix, thanks! Stefan signature.asc Description: PGP signature
Re: [PATCH 1/6] block: add blk_io_plug_call() API
On Fri, May 19, 2023 at 10:45:57AM +0200, Stefano Garzarella wrote:
> On Wed, May 17, 2023 at 06:10:17PM -0400, Stefan Hajnoczi wrote:
> > Introduce a new API for thread-local blk_io_plug() that does not
> > traverse the block graph. The goal is to make blk_io_plug() multi-queue
> > friendly.
> >
> > Instead of having block drivers track whether or not we're in a plugged
> > section, provide an API that allows them to defer a function call until
> > we're unplugged: blk_io_plug_call(fn, opaque). If blk_io_plug_call() is
> > called multiple times with the same fn/opaque pair, then fn() is only
> > called once at the end of the function - resulting in batching.
> >
> > This patch introduces the API and changes blk_io_plug()/blk_io_unplug().
> > blk_io_plug()/blk_io_unplug() no longer require a BlockBackend argument
> > because the plug state is now thread-local.
> >
> > Later patches convert block drivers to blk_io_plug_call() and then we
> > can finally remove .bdrv_co_io_plug() once all block drivers have been
> > converted.
> >
> > Signed-off-by: Stefan Hajnoczi
> > ---
> > MAINTAINERS | 1 +
> > include/sysemu/block-backend-io.h | 13 +--
> > block/block-backend.c | 22 -
> > block/plug.c | 159 ++
> > hw/block/dataplane/xen-block.c| 8 +-
> > hw/block/virtio-blk.c | 4 +-
> > hw/scsi/virtio-scsi.c | 6 +-
> > block/meson.build | 1 +
> > 8 files changed, 173 insertions(+), 41 deletions(-)
> > create mode 100644 block/plug.c
> >
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index 50585117a0..574202295c 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -2644,6 +2644,7 @@ F: util/aio-*.c
> > F: util/aio-*.h
> > F: util/fdmon-*.c
> > F: block/io.c
> > +F: block/plug.c
> > F: migration/block*
> > F: include/block/aio.h
> > F: include/block/aio-wait.h
> > diff --git a/include/sysemu/block-backend-io.h
> > b/include/sysemu/block-backend-io.h
> > index d62a7ee773..be4dcef59d 100644
> > --- a/include/sysemu/block-backend-io.h
> > +++ b/include/sysemu/block-backend-io.h
> > @@ -100,16 +100,9 @@ void blk_iostatus_set_err(BlockBackend *blk, int
> > error);
> > int blk_get_max_iov(BlockBackend *blk);
> > int blk_get_max_hw_iov(BlockBackend *blk);
> >
> > -/*
> > - * blk_io_plug/unplug are thread-local operations. This means that multiple
> > - * IOThreads can simultaneously call plug/unplug, but the caller must
> > ensure
> > - * that each unplug() is called in the same IOThread of the matching
> > plug().
> > - */
> > -void coroutine_fn blk_co_io_plug(BlockBackend *blk);
> > -void co_wrapper blk_io_plug(BlockBackend *blk);
> > -
> > -void coroutine_fn blk_co_io_unplug(BlockBackend *blk);
> > -void co_wrapper blk_io_unplug(BlockBackend *blk);
> > +void blk_io_plug(void);
> > +void blk_io_unplug(void);
> > +void blk_io_plug_call(void (*fn)(void *), void *opaque);
> >
> > AioContext *blk_get_aio_context(BlockBackend *blk);
> > BlockAcctStats *blk_get_stats(BlockBackend *blk);
> > diff --git a/block/block-backend.c b/block/block-backend.c
> > index ca537cd0ad..1f1d226ba6 100644
> > --- a/block/block-backend.c
> > +++ b/block/block-backend.c
> > @@ -2568,28 +2568,6 @@ void blk_add_insert_bs_notifier(BlockBackend *blk,
> > Notifier *notify)
> > notifier_list_add(>insert_bs_notifiers, notify);
> > }
> >
> > -void coroutine_fn blk_co_io_plug(BlockBackend *blk)
> > -{
> > -BlockDriverState *bs = blk_bs(blk);
> > -IO_CODE();
> > -GRAPH_RDLOCK_GUARD();
> > -
> > -if (bs) {
> > -bdrv_co_io_plug(bs);
> > -}
> > -}
> > -
> > -void coroutine_fn blk_co_io_unplug(BlockBackend *blk)
> > -{
> > -BlockDriverState *bs = blk_bs(blk);
> > -IO_CODE();
> > -GRAPH_RDLOCK_GUARD();
> > -
> > -if (bs) {
> > -bdrv_co_io_unplug(bs);
> > -}
> > -}
> > -
> > BlockAcctStats *blk_get_stats(BlockBackend *blk)
> > {
> > IO_CODE();
> > diff --git a/block/plug.c b/block/plug.c
> > new file mode 100644
> > index 00..6738a568ba
> > --- /dev/null
> > +++ b/block/plug.c
> > @@ -0,0 +1,159 @@
> > +/* SPDX-License-Identifier: GPL-2.0-or-later */
> > +/*
> > + * Block I/O plugging
> > + *
> > + * Copyright Red Hat.
> > + *
> > + * This API defers a function call within a blk_io_plug()/blk_io_unplug()
> > + * section, allowing multiple calls to batch up. This is a performance
> > + * optimization that is used in the block layer to submit several I/O
> > requests
> > + * at once instead of individually:
> > + *
> > + * blk_io_plug(); <-- start of plugged region
> > + * ...
> > + * blk_io_plug_call(my_func, my_obj); <-- deferred my_func(my_obj) call
> > + * blk_io_plug_call(my_func, my_obj); <-- another
> > + * blk_io_plug_call(my_func, my_obj); <-- another
> > + * ...
> > + * blk_io_unplug(); <-- end of plugged region, my_func(my_obj) is called
> > once
> > + *
> > + * This code is actually generic and not tied to the
Re: [PATCH 1/6] block: add blk_io_plug_call() API
On Wed, May 17, 2023 at 06:10:17PM -0400, Stefan Hajnoczi wrote:
Introduce a new API for thread-local blk_io_plug() that does not
traverse the block graph. The goal is to make blk_io_plug() multi-queue
friendly.
Instead of having block drivers track whether or not we're in a plugged
section, provide an API that allows them to defer a function call until
we're unplugged: blk_io_plug_call(fn, opaque). If blk_io_plug_call() is
called multiple times with the same fn/opaque pair, then fn() is only
called once at the end of the function - resulting in batching.
This patch introduces the API and changes blk_io_plug()/blk_io_unplug().
blk_io_plug()/blk_io_unplug() no longer require a BlockBackend argument
because the plug state is now thread-local.
Later patches convert block drivers to blk_io_plug_call() and then we
can finally remove .bdrv_co_io_plug() once all block drivers have been
converted.
Signed-off-by: Stefan Hajnoczi
---
MAINTAINERS | 1 +
include/sysemu/block-backend-io.h | 13 +--
block/block-backend.c | 22 -
block/plug.c | 159 ++
hw/block/dataplane/xen-block.c| 8 +-
hw/block/virtio-blk.c | 4 +-
hw/scsi/virtio-scsi.c | 6 +-
block/meson.build | 1 +
8 files changed, 173 insertions(+), 41 deletions(-)
create mode 100644 block/plug.c
diff --git a/MAINTAINERS b/MAINTAINERS
index 50585117a0..574202295c 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2644,6 +2644,7 @@ F: util/aio-*.c
F: util/aio-*.h
F: util/fdmon-*.c
F: block/io.c
+F: block/plug.c
F: migration/block*
F: include/block/aio.h
F: include/block/aio-wait.h
diff --git a/include/sysemu/block-backend-io.h
b/include/sysemu/block-backend-io.h
index d62a7ee773..be4dcef59d 100644
--- a/include/sysemu/block-backend-io.h
+++ b/include/sysemu/block-backend-io.h
@@ -100,16 +100,9 @@ void blk_iostatus_set_err(BlockBackend *blk, int error);
int blk_get_max_iov(BlockBackend *blk);
int blk_get_max_hw_iov(BlockBackend *blk);
-/*
- * blk_io_plug/unplug are thread-local operations. This means that multiple
- * IOThreads can simultaneously call plug/unplug, but the caller must ensure
- * that each unplug() is called in the same IOThread of the matching plug().
- */
-void coroutine_fn blk_co_io_plug(BlockBackend *blk);
-void co_wrapper blk_io_plug(BlockBackend *blk);
-
-void coroutine_fn blk_co_io_unplug(BlockBackend *blk);
-void co_wrapper blk_io_unplug(BlockBackend *blk);
+void blk_io_plug(void);
+void blk_io_unplug(void);
+void blk_io_plug_call(void (*fn)(void *), void *opaque);
AioContext *blk_get_aio_context(BlockBackend *blk);
BlockAcctStats *blk_get_stats(BlockBackend *blk);
diff --git a/block/block-backend.c b/block/block-backend.c
index ca537cd0ad..1f1d226ba6 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -2568,28 +2568,6 @@ void blk_add_insert_bs_notifier(BlockBackend *blk,
Notifier *notify)
notifier_list_add(>insert_bs_notifiers, notify);
}
-void coroutine_fn blk_co_io_plug(BlockBackend *blk)
-{
-BlockDriverState *bs = blk_bs(blk);
-IO_CODE();
-GRAPH_RDLOCK_GUARD();
-
-if (bs) {
-bdrv_co_io_plug(bs);
-}
-}
-
-void coroutine_fn blk_co_io_unplug(BlockBackend *blk)
-{
-BlockDriverState *bs = blk_bs(blk);
-IO_CODE();
-GRAPH_RDLOCK_GUARD();
-
-if (bs) {
-bdrv_co_io_unplug(bs);
-}
-}
-
BlockAcctStats *blk_get_stats(BlockBackend *blk)
{
IO_CODE();
diff --git a/block/plug.c b/block/plug.c
new file mode 100644
index 00..6738a568ba
--- /dev/null
+++ b/block/plug.c
@@ -0,0 +1,159 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Block I/O plugging
+ *
+ * Copyright Red Hat.
+ *
+ * This API defers a function call within a blk_io_plug()/blk_io_unplug()
+ * section, allowing multiple calls to batch up. This is a performance
+ * optimization that is used in the block layer to submit several I/O requests
+ * at once instead of individually:
+ *
+ * blk_io_plug(); <-- start of plugged region
+ * ...
+ * blk_io_plug_call(my_func, my_obj); <-- deferred my_func(my_obj) call
+ * blk_io_plug_call(my_func, my_obj); <-- another
+ * blk_io_plug_call(my_func, my_obj); <-- another
+ * ...
+ * blk_io_unplug(); <-- end of plugged region, my_func(my_obj) is called once
+ *
+ * This code is actually generic and not tied to the block layer. If another
+ * subsystem needs this functionality, it could be renamed.
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/coroutine-tls.h"
+#include "qemu/notify.h"
+#include "qemu/thread.h"
+#include "sysemu/block-backend.h"
+
+/* A function call that has been deferred until unplug() */
+typedef struct {
+void (*fn)(void *);
+void *opaque;
+} UnplugFn;
+
+/* Per-thread state */
+typedef struct {
+unsigned count; /* how many times has plug() been called? */
+GArray *unplug_fns; /* functions to call at unplug time */
+} Plug;
+
+/* Use get_ptr_plug() to fetch this
Re: [PATCH 1/6] block: add blk_io_plug_call() API
On Wed, May 17, 2023 at 06:10:17PM -0400, Stefan Hajnoczi wrote: > Introduce a new API for thread-local blk_io_plug() that does not > traverse the block graph. The goal is to make blk_io_plug() multi-queue > friendly. > > Instead of having block drivers track whether or not we're in a plugged > section, provide an API that allows them to defer a function call until > we're unplugged: blk_io_plug_call(fn, opaque). If blk_io_plug_call() is > called multiple times with the same fn/opaque pair, then fn() is only > called once at the end of the function - resulting in batching. > > This patch introduces the API and changes blk_io_plug()/blk_io_unplug(). > blk_io_plug()/blk_io_unplug() no longer require a BlockBackend argument > because the plug state is now thread-local. > > Later patches convert block drivers to blk_io_plug_call() and then we > can finally remove .bdrv_co_io_plug() once all block drivers have been > converted. > > Signed-off-by: Stefan Hajnoczi > --- > +++ b/block/plug.c > + > +/** > + * blk_io_plug_call: > + * @fn: a function pointer to be invoked > + * @opaque: a user-defined argument to @fn() > + * > + * Call @fn(@opaque) immediately if not within a > blk_io_plug()/blk_io_unplug() > + * section. > + * > + * Otherwise defer the call until the end of the outermost > + * blk_io_plug()/blk_io_unplug() section in this thread. If the same > + * @fn/@opaque pair has already been deferred, it will only be called once > upon > + * blk_io_unplug() so that accumulated calls are batched into a single call. > + * > + * The caller must ensure that @opaque is not be freed before @fn() is > invoked. s/be // > + */ > +void blk_io_plug_call(void (*fn)(void *), void *opaque) Reviewed-by: Eric Blake -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org
[PATCH 1/6] block: add blk_io_plug_call() API
Introduce a new API for thread-local blk_io_plug() that does not
traverse the block graph. The goal is to make blk_io_plug() multi-queue
friendly.
Instead of having block drivers track whether or not we're in a plugged
section, provide an API that allows them to defer a function call until
we're unplugged: blk_io_plug_call(fn, opaque). If blk_io_plug_call() is
called multiple times with the same fn/opaque pair, then fn() is only
called once at the end of the function - resulting in batching.
This patch introduces the API and changes blk_io_plug()/blk_io_unplug().
blk_io_plug()/blk_io_unplug() no longer require a BlockBackend argument
because the plug state is now thread-local.
Later patches convert block drivers to blk_io_plug_call() and then we
can finally remove .bdrv_co_io_plug() once all block drivers have been
converted.
Signed-off-by: Stefan Hajnoczi
---
MAINTAINERS | 1 +
include/sysemu/block-backend-io.h | 13 +--
block/block-backend.c | 22 -
block/plug.c | 159 ++
hw/block/dataplane/xen-block.c| 8 +-
hw/block/virtio-blk.c | 4 +-
hw/scsi/virtio-scsi.c | 6 +-
block/meson.build | 1 +
8 files changed, 173 insertions(+), 41 deletions(-)
create mode 100644 block/plug.c
diff --git a/MAINTAINERS b/MAINTAINERS
index 50585117a0..574202295c 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2644,6 +2644,7 @@ F: util/aio-*.c
F: util/aio-*.h
F: util/fdmon-*.c
F: block/io.c
+F: block/plug.c
F: migration/block*
F: include/block/aio.h
F: include/block/aio-wait.h
diff --git a/include/sysemu/block-backend-io.h
b/include/sysemu/block-backend-io.h
index d62a7ee773..be4dcef59d 100644
--- a/include/sysemu/block-backend-io.h
+++ b/include/sysemu/block-backend-io.h
@@ -100,16 +100,9 @@ void blk_iostatus_set_err(BlockBackend *blk, int error);
int blk_get_max_iov(BlockBackend *blk);
int blk_get_max_hw_iov(BlockBackend *blk);
-/*
- * blk_io_plug/unplug are thread-local operations. This means that multiple
- * IOThreads can simultaneously call plug/unplug, but the caller must ensure
- * that each unplug() is called in the same IOThread of the matching plug().
- */
-void coroutine_fn blk_co_io_plug(BlockBackend *blk);
-void co_wrapper blk_io_plug(BlockBackend *blk);
-
-void coroutine_fn blk_co_io_unplug(BlockBackend *blk);
-void co_wrapper blk_io_unplug(BlockBackend *blk);
+void blk_io_plug(void);
+void blk_io_unplug(void);
+void blk_io_plug_call(void (*fn)(void *), void *opaque);
AioContext *blk_get_aio_context(BlockBackend *blk);
BlockAcctStats *blk_get_stats(BlockBackend *blk);
diff --git a/block/block-backend.c b/block/block-backend.c
index ca537cd0ad..1f1d226ba6 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -2568,28 +2568,6 @@ void blk_add_insert_bs_notifier(BlockBackend *blk,
Notifier *notify)
notifier_list_add(>insert_bs_notifiers, notify);
}
-void coroutine_fn blk_co_io_plug(BlockBackend *blk)
-{
-BlockDriverState *bs = blk_bs(blk);
-IO_CODE();
-GRAPH_RDLOCK_GUARD();
-
-if (bs) {
-bdrv_co_io_plug(bs);
-}
-}
-
-void coroutine_fn blk_co_io_unplug(BlockBackend *blk)
-{
-BlockDriverState *bs = blk_bs(blk);
-IO_CODE();
-GRAPH_RDLOCK_GUARD();
-
-if (bs) {
-bdrv_co_io_unplug(bs);
-}
-}
-
BlockAcctStats *blk_get_stats(BlockBackend *blk)
{
IO_CODE();
diff --git a/block/plug.c b/block/plug.c
new file mode 100644
index 00..6738a568ba
--- /dev/null
+++ b/block/plug.c
@@ -0,0 +1,159 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Block I/O plugging
+ *
+ * Copyright Red Hat.
+ *
+ * This API defers a function call within a blk_io_plug()/blk_io_unplug()
+ * section, allowing multiple calls to batch up. This is a performance
+ * optimization that is used in the block layer to submit several I/O requests
+ * at once instead of individually:
+ *
+ * blk_io_plug(); <-- start of plugged region
+ * ...
+ * blk_io_plug_call(my_func, my_obj); <-- deferred my_func(my_obj) call
+ * blk_io_plug_call(my_func, my_obj); <-- another
+ * blk_io_plug_call(my_func, my_obj); <-- another
+ * ...
+ * blk_io_unplug(); <-- end of plugged region, my_func(my_obj) is called once
+ *
+ * This code is actually generic and not tied to the block layer. If another
+ * subsystem needs this functionality, it could be renamed.
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/coroutine-tls.h"
+#include "qemu/notify.h"
+#include "qemu/thread.h"
+#include "sysemu/block-backend.h"
+
+/* A function call that has been deferred until unplug() */
+typedef struct {
+void (*fn)(void *);
+void *opaque;
+} UnplugFn;
+
+/* Per-thread state */
+typedef struct {
+unsigned count; /* how many times has plug() been called? */
+GArray *unplug_fns; /* functions to call at unplug time */
+} Plug;
+
+/* Use get_ptr_plug() to fetch this thread-local value */
