Re: [PATCH 2.5] Report write errors to applications

[Andrew Morton <akpm@digeo.com>]

Oliver Xymoron wrote:
> 
> On Wed, Jan 29, 2003 at 01:42:05PM -0800, Andrew Morton wrote:
> > Oliver Xymoron <oxymoron@waste.org> wrote:
> > >
> > > > - fsync_buffers_list() will handle them and will return errors to the fsync()
> > > > caller.  We only need to handle those buffers which were stripped
> > > > asynchronously by VM activity.
> > >
> > > Are we guaranteed that we'll get a try_to_free_buffers after IO
> > > completion and before sync? I haven't dug through this path much.
> >
> > Think so.  That's the only place where buffers are detached.  Otherwise,
> > fsync_buffers_list() looks at them all.
> 
> The other problem here is that by the time we're in
> try_to_free_buffers we no longer know that we're looking at a harmless
> stale page (readahead?) or a write error, which is why Linus had me
> make the separate end_buffer functions. So I don't think this pans out
> - thoughts?

If the buffer has buffer_req and !buffer_uptodate and !buffer_locked
we know that it was submitted for IO, that the IO has completed, and
that it failed.