On Tue, Nov 03, 2020 at 09:00:45AM +0100, Christoph Hellwig wrote:
> On Mon, Nov 02, 2020 at 06:43:10PM +0000, Matthew Wilcox (Oracle) wrote:
> > We don't need to get the page lock again; we just need to wait for
> > the I/O to finish, so use wait_on_page_locked_killable() like the
> > other callers of ->readpage.
>
> As that isn't entirely obvious, what about adding a comment next to
> the wait_on_page_locked_killable call to document it?
The other callers of ->readpage don't document that, so not sure why
we should here?
> > + error = wait_on_page_locked_killable(page);
> > if (error)
> > return error;
> > + if (PageUptodate(page))
> > + return 0;
> > + if (!page->mapping) /* page truncated */
> > + return AOP_TRUNCATED_PAGE;
> > + shrink_readahead_size_eio(&file->f_ra);
> > + return -EIO;
>
> You might notice a theme here, but I hate having the fast path exit
> early without a good reason, so I'd be much happier with:
>
> if (!PageUptodate(page)) {
> if (!page->mapping) /* page truncated */
> return AOP_TRUNCATED_PAGE;
> shrink_readahead_size_eio(&file->f_ra);
> return -EIO;
> }
> return 0;
I'm just not a fan of unnecessary indentation.
