[PATCH 4/4] ubifs: Convert do_writepage() to take a folio

[Richard Weinberger]

----- Ursprüngliche Mail -----
> Von: "Matthew Wilcox" <willy at infradead.org>
> On Tue, Jun 06, 2023 at 08:13:55AM +0200, Richard Weinberger wrote:
>> Matthew,
>> 
>> ----- Ursprüngliche Mail -----
>> > Von: "Matthew Wilcox" <willy at infradead.org>
>> > len is folio_size(), which is not 0.
>> > 
>> >        len = offset_in_folio(folio, i_size);
>> 
>> offset_in_folio(folio, i_size) can give 0.
> 
> Oh!  There is a bug, because it shouldn't get here!
> 
>        /* Is the folio fully inside i_size? */
>        if (folio_pos(folio) + len < i_size) {
> 
> should be:
> 
>        /* Is the folio fully inside i_size? */
>        if (folio_pos(folio) + len <= i_size) {
> 
> right?  Consider a file with i_size 4096.  its single-page folio will
> have a pos of 0 and a length of 4096.  so it should be written back by
> the first call to do_writepage(), not the case where the folio straddles
> i_size.

Indeed.
With that change I agree that do_writepage() cannot get called with zero len.
I'll run more tests, so far all is nice an shiny. :-)

Thanks,
//richard