Re: [PATCH 1/3] vfs: dedpue: return s64

[Miklos Szeredi]

On Mon, May 7, 2018 at 1:11 PM, Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote:
> On Mon, May 07, 2018 at 10:21:06AM +0200, Miklos Szeredi wrote:
>> f_op->dedupe_file_range() gets a u64 length to dedup and returns an ssize_t
>> actual length deduped.  This breaks badly on 32bit archs since the returned
>> length will be truncated and possibly overflow into the sign bit (xfs and
>> ocfs2 are affected, btrfs limits actual length to 16MiB).
>>
>> Returning s64 should be good, since clone_verify_area() makes sure that the
>> supplied length doesn't overflow.
>
> Why s64 rather than loff_t?  Particularly since the next patch turns
> the paramters into loff_t.

Next patch turns the offsets into loff_t and leaves "len" as u64.  A
size is definitely not an offset, I'd consider changing the type of
"len" to loff_t a misuse.

Thanks,
Miklos