linux-kernel - Re: [PATCH] nvdimm: virtio_pmem: serialize flush requests

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Message-ID: <6980dc5569d5a_3430210092@iweiny-mobl.notmuch>
Date: Mon, 2 Feb 2026 11:18:13 -0600
From: Ira Weiny <ira.weiny@...el.com>
To: "Michael S. Tsirkin" <mst@...hat.com>, Ira Weiny <ira.weiny@...el.com>
CC: Li Chen <me@...ux.beauty>, Dan Williams <dan.j.williams@...el.com>,
	"Vishal Verma" <vishal.l.verma@...el.com>, Dave Jiang <dave.jiang@...el.com>,
	"Pankaj Gupta" <pankaj.gupta.linux@...il.com>, Cornelia Huck
	<cohuck@...hat.com>, Jakub Staron <jstaron@...gle.com>,
	<nvdimm@...ts.linux.dev>, <virtualization@...ts.linux.dev>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] nvdimm: virtio_pmem: serialize flush requests

Michael S. Tsirkin wrote:
> On Fri, Jan 30, 2026 at 02:52:12PM -0600, Ira Weiny wrote:
> > Li Chen wrote:

[snip]

> > > diff --git a/drivers/nvdimm/nd_virtio.c b/drivers/nvdimm/nd_virtio.c
> > > index c3f07be4aa22..827a17fe7c71 100644
> > > --- a/drivers/nvdimm/nd_virtio.c
> > > +++ b/drivers/nvdimm/nd_virtio.c
> > > @@ -44,19 +44,24 @@ static int virtio_pmem_flush(struct nd_region *nd_region)
> > >  	unsigned long flags;
> > >  	int err, err1;
> > >  
> > > +	might_sleep();
> > > +	mutex_lock(&vpmem->flush_lock);
> > 
> > Assuming this does fix a bug I'd rather use guard here.
> 
> Do you, from code review, agree with the logic that
> it's racy right now?

I do now.  I was hoping to understand the test being run.  The additional
detail that it takes multiple runs helps.

> Whether the bug is reproducible isn't really the question.
> 

True.  But we should still use guard().  I'll look for v2.

Ira