Re: [PATCH 11/13] block/fuse: take AioContext lock around blk_exp_ref/unref()

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Tue, Apr 04, 2023 at 03:46:34PM +0200, Paolo Bonzini wrote:
> On 4/3/23 20:30, Stefan Hajnoczi wrote:
> > These functions must be called with the AioContext acquired:
> > 
> >    /* Callers must hold exp->ctx lock */
> >    void blk_exp_ref(BlockExport *exp)
> >    ...
> >    /* Callers must hold exp->ctx lock */
> >    void blk_exp_unref(BlockExport *exp)
> > 
> > Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> > ---
> >   block/export/fuse.c | 4 ++++
> >   1 file changed, 4 insertions(+)
> > 
> > diff --git a/block/export/fuse.c b/block/export/fuse.c
> > index 06fa41079e..18394f9e07 100644
> > --- a/block/export/fuse.c
> > +++ b/block/export/fuse.c
> > @@ -244,7 +244,9 @@ static void read_from_fuse_export(void *opaque)
> >       FuseExport *exp = opaque;
> >       int ret;
> > +    aio_context_acquire(exp->common.ctx);
> >       blk_exp_ref(&exp->common);
> > +    aio_context_release(exp->common.ctx);
> >       do {
> >           ret = fuse_session_receive_buf(exp->fuse_session, &exp->fuse_buf);
> > @@ -256,7 +258,9 @@ static void read_from_fuse_export(void *opaque)
> >       fuse_session_process_buf(exp->fuse_session, &exp->fuse_buf);
> >   out:
> > +    aio_context_acquire(exp->common.ctx);
> >       blk_exp_unref(&exp->common);
> > +    aio_context_release(exp->common.ctx);
> >   }
> 
> Since the actual thread-unsafe work is done in a bottom half, perhaps
> instead you can use qatomic_inc and qatomic_fetch_dec in
> blk_exp_{ref,unref}?

Sure, I'll give that a try in the next revision.

Stefan

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