Re: [PATCH 01/15] ubifs: Set page uptodate in the correct place

Matthew Wilcox
2024-01-24T05:02:07Z

On Tue, Jan 23, 2024 at 10:36:14AM +0800, Zhihao Cheng wrote:
> 在 2024/1/22 22:40, Matthew Wilcox 写道:
> > On Mon, Jan 22, 2024 at 03:22:45PM +0800, Zhihao Cheng wrote:
> > > 在 2024/1/21 7:08, Matthew Wilcox (Oracle) 写道:
> > > > Page cache reads are lockless, so setting the freshly allocated page
> > > > uptodate before we've overwritten it with the data it's supposed to have
> > > > in it will allow a simultaneous reader to see old data. Move the call
> > > > to SetPageUptodate into ubifs_write_end(), which is after we copied the
> > > > new data into the page.
> > >
> > > This solution looks good to me, and I think 'SetPageUptodate' should be
> > > removed from write_begin_slow(slow path) too.
> >
> > I didn't bother because we have just read into the page so it is
> > uptodate. A racing read will see the data from before the write, but
> > that's an acceptable ordering of events.
> > .
> >
>
> I can't find where the page is read and set uptodate. I think the
> uninitialized data can be found in following path:

You're right; thanks. I'd misread the code. I'll send a new version in
a few hours.