Re: [PATCH 1/2] fs: add support for LOOKUP_NONBLOCK

[Jens Axboe <axboe@kernel.dk>]

On 12/10/20 1:53 PM, Linus Torvalds wrote:
> On Thu, Dec 10, 2020 at 12:01 PM Jens Axboe <axboe@kernel.dk> wrote:
>>
>> io_uring always punts opens to async context, since there's no control
>> over whether the lookup blocks or not. Add LOOKUP_NONBLOCK to support
>> just doing the fast RCU based lookups, which we know will not block. If
>> we can do a cached path resolution of the filename, then we don't have
>> to always punt lookups for a worker.
> 
> Ok, this looks much better to me just from the name change.
> 
> Half of the patch is admittedly just to make sure it now returns the
> right error from unlazy_walk (rather than knowing it's always
> -ECHILD), and that could be its own thing, but I'm not sure it's even
> worth splitting up. The only reason to do it would be to perhaps make
> it really clear which part is the actual change, and which is just
> that error handling cleanup.
> 
> So it looks fine to me, but I will leave this all to Al.

I did consider doing a prep patch just making the error handling clearer
and get rid of the -ECHILD assumption, since it's pretty odd and not
even something I'd expect to see in there. Al, do you want a prep patch
to do that to make the change simpler/cleaner?

-- 
Jens Axboe