Re: [PATCH 18/21] iomap: Convert iomap_add_to_ioend to take a folio

Matthew Wilcox
2021-11-04T03:35:35Z

On Wed, Nov 03, 2021 at 08:54:50AM -0700, Christoph Hellwig wrote:
> > - * Walk through the page to find areas to write back. If we run off the
> > - * end of the current map or find the current map invalid, grab a new
> > - * one.
> > + * Walk through the folio to find areas to write back. If we
> > + * run off the end of the current map or find the current map
> > + * invalid, grab a new one.
>
> No real need for reflowing the comment, it still fits just fine even
> with the folio change.

Sure, but I don't like using column 79, unless it's better to. We're on
three lines anyway; may as well make better use of that third line.

> > + isize = i_size_read(inode);
> > + end_pos = page_offset(page) + PAGE_SIZE;
> > + if (end_pos - 1 >= isize) {
>
> Wouldn't this check be more obvious as:
>
> if (end_pos > i_size) {

I _think_ we restrict the maximum file size to 2^63 - 1 to avoid i_size
ever being negative. But that means that end_pos might be 2^63 (ie
LONG_MIN), so we need to subtract one from it to get the right answer.
Maybe worth a comment?