Re: [PATCH v2] xfs: fix incorrect log_flushed on fsync

[Brian Foster <bfoster@redhat.com>]

On Wed, Sep 06, 2017 at 03:19:37PM +0200, Christoph Hellwig wrote:
> > You could also say that flush sequence counting code doesn't belong
> > to xfs code at all. There is nothing xfs specific about it.
> > 
> > If we had an API:
> > 
> > flush_seq = blkdev_get_flush_seq(bdev, flush_seq);
> > blkdev_issue_flush_after(bdev, flush_seq);
> > 
> > I am sure it would have been useful to more fs.
> > 
> > In fact, block drivers that use blk_insert_flush(),
> > already have serialized flush requests, so implementing
> > the above functionality would be quite trivial for those.
> > 
> > I am not fluent enough in block layer to say if this makes sense.
> > Christoph? Should we add some block people to this discussion?
> 
> Not that the interface can't be based on blkdev_issue_flush as
> our most important flushes are submitted asynchronously.
> 
> But except for that tying into the flush state machine sounds
> very interesting.  Let me look into that as the designate
> xfs <-> block layer liaison.

That sounds like a nice idea to me, particularly if there is potential
for other users. I'll wait to look into doing anything in XFS until we
see how this turns out. Thanks.

Brian

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