Re: [PATCH 1/6] block: add blk_io_plug_call() API

[Stefan Hajnoczi <stefanha@redhat.com>]

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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 <stefanha@redhat.com>
> > ---
> 
> > +++ 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

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