Re: [git pull] iov_iter fixes

[Jens Axboe]

On 9/10/21 9:32 AM, Al Viro wrote:
> On Fri, Sep 10, 2021 at 09:08:02AM -0600, Jens Axboe wrote:
> 
>>> You actually can cut it down even more - nr_segs + iov remains constant
>>> all along, so you could get away with just 3 words here...  I would be
>>
>> Mmm, the iov pointer remains constant? Maybe I'm missing your point, but
>> the various advance functions are quite happy to increment iter->iov or
>> iter->bvec, so we need to restore them. From a quick look, looks like
>> iter->nr_segs is modified for advancing too.
>>
>> What am I missing?
> 
> i->iov + i->nr_segs does not change - the places incrementing the former
> will decrement the latter by the same amount.  So it's enough to store
> either of those - the other one can be recovered by subtracting the
> saved value from the current i->iov + i->nr_segs.

Ahh, clever. Yes that should work just fine. Let me test that and send
out a proposal. Thanks Al.

-- 
Jens Axboe