Re: [GIT PULL] Btrfs updates for 5.13

[Matthew Wilcox]

On Mon, Apr 26, 2021 at 01:55:03PM -0700, Linus Torvalds wrote:
> I've pulled this, but:
> 
> On Mon, Apr 26, 2021 at 1:01 PM David Sterba <dsterba@xxxxxxxx> wrote:
> >
> > Matthew Wilcox (Oracle) (1):
> >       btrfs: add and use readahead_batch_length
> 
> This one is buggy, or at least questionable.
> 
> Yes, yes, the function looks trivial. That doesn't make it right:
> 
>   static inline loff_t readahead_batch_length(struct readahead_control *rac)
>   {
>           return rac->_batch_count * PAGE_SIZE;
>   }
> 
> the above does not get the types right, and silently does different
> typecasting than the code clearly intends from the return type of the
> function.
> 
> It may not matter much in practice, but it's still wrong.

Thanks.  You're right that it doesn't matter in practice (because a
batch length is always much, much less than 4GB), but I'll fix it to
return a size_t (which is just the obvious s/loff_t/size_t/, because
PAGE_SIZE is an unsigned long).