Messages in this thread | | | Date | Wed, 15 Feb 2023 12:33:08 -0800 | From | Josh Triplett <> | Subject | Re: [PATCHv2] io_uring: Support calling io_uring_register with a registered ring fd |
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On Wed, Feb 15, 2023 at 10:44:38AM -0700, Jens Axboe wrote: > On 2/14/23 5:42 PM, Josh Triplett wrote: > > Add a new flag IORING_REGISTER_USE_REGISTERED_RING (set via the high bit > > of the opcode) to treat the fd as a registered index rather than a file > > descriptor. > > > > This makes it possible for a library to open an io_uring, register the > > ring fd, close the ring fd, and subsequently use the ring entirely via > > registered index. > > This looks pretty straight forward to me, only real question I had > was whether using the top bit of the register opcode for this is the > best choice. But I can't think of better ways to do it, and the space > is definitely big enough to do that, so looks fine to me.
It seemed like the cleanest way available given the ABI of io_uring_register, yeah.
> One more comment below: > > > + if (use_registered_ring) { > > + /* > > + * Ring fd has been registered via IORING_REGISTER_RING_FDS, we > > + * need only dereference our task private array to find it. > > + */ > > + struct io_uring_task *tctx = current->io_uring; > > I need to double check if it's guaranteed we always have current->io_uring > assigned here. If the ring is registered we certainly will have it, but > what if someone calls io_uring_register(2) without having a ring setup > upfront? > > IOW, I think we need a NULL check here and failing the request at that > point.
The next line is:
+ if (unlikely(!tctx || fd >= IO_RINGFD_REG_MAX))
The first part of that condition is the NULL check you're looking for, right?
- Josh Triplett
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