Re: [PATCH 01/67] mm: Stop filemap_read() from grabbing a superfluous page

Matthew Wilcox
2021-10-19T20:08:27Z

On Tue, Oct 19, 2021 at 07:48:15PM +0100, David Howells wrote:
> Matthew Wilcox <willy@infradead.org> wrote:
>
> > > + isize = i_size_read(inode);
> > > + if (unlikely(iocb->ki_pos >= isize))
> > > + goto put_pages;
> > > +
> >
> > Is there a good reason to assign to isize here? I'd rather not,
> > because it complicates analysis, and a later change might look at
> > the isize read here, not realising it was a racy use. So I'd
> > rather see:
>
> If we don't set isize, the loop will never end. Actually, maybe we can just
> break out at that point rather than going to put_pages.

Umm, yes, of course. Sorry.

It makes more sense to just break because we haven't got any pages,
so putting pages that we haven't got seems unnecessary.
>