Re: [PATCH] dirty pages in memory & co.

["Benjamin C.R. LaHaise" <blah@kvack.org>]

On Mon, 10 May 1999, Stephen C. Tweedie wrote:

> On 07 May 1999 09:56:00 -0500, ebiederm+eric@ccr.net (Eric W. Biederman)
> said:
> 
> >        It looks like I need 2 variations on generic_file_write at the
> >        moment. 
> >        1) for network filesystems that can get away without filling
> >           the page on a partial write.
> >        2) for block based filesystems that must fill the page on a
> >           partial write because they can't write arbitrary chunks of
> >           data.
> 
> I'd be very worried by (1): sounds like a partial write followed by a
> read of the full page could show up garbage in the page cache if you do
> this.  If NFS skips the page clearing for partial writes, how does it
> avoid returning garbage later?

Hmmm, it shouldn't be a problem if the write blocks the reading of the
page and PG_uptodate isn't set.  This conflicts with the current
assumption in generic_file_read that a locked page becoming unlocked
without PG_uptodate being set indicates an error -- the best thing here
is probably to add a PG_error flag and do away with the overloading.
Everything else should be checking PG_uptodate, right?

		-ben

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