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

[Matthew Wilcox]

On Tue, Oct 19, 2021 at 07:48:15PM +0100, David Howells wrote:
> Matthew Wilcox <willy@xxxxxxxxxxxxx> 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.
>