On Wed, 3 Mar 2021 01:33:13 +0000 Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote:
> On Tue, Mar 02, 2021 at 05:30:39PM -0800, Andrew Morton wrote:
> > On Fri, 26 Feb 2021 14:00:11 +0000 "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx> wrote:
> >
> > > After splitting generic_file_buffered_read() into smaller parts, it
> > > turns out we can reuse one of the parts in filemap_fault(). This fixes
> > > an oversight -- waiting for the I/O to complete is now interruptible
> > > by a fatal signal. And it saves us a few bytes of text in an unlikely
> > > path.
> >
> > We also handle AOP_TRUNCATED_PAGE which the present code fails to do.
> > Should this be in the changelog?
>
> No, the present code does handle AOP_TRUNCATED_PAGE. It's perhaps not
> the clearest in the diff, but it's there. Here's git show -U5:
>
> - ClearPageError(page);
> fpin = maybe_unlock_mmap_for_io(vmf, fpin);
> - error = mapping->a_ops->readpage(file, page);
> - if (!error) {
> - wait_on_page_locked(page);
> - if (!PageUptodate(page))
> - error = -EIO;
> - }
> + error = filemap_read_page(file, mapping, page);
> if (fpin)
> goto out_retry;
> put_page(page);
>
> if (!error || error == AOP_TRUNCATED_PAGE)
> goto retry_find;
>
> - shrink_readahead_size_eio(ra);
> return VM_FAULT_SIGBUS;
But ->readpage() doesn't check for !mapping (does it?). So the
->readpage() cannot return AOP_TRUNCATED_PAGE.
However filemap_read_page() does check for !mapping. So current -linus
doesn't check for !mapping, and post-willy does do this?
