Re: [PATCH v1 03/11] io_uring/kbuf: add support for kernel-managed buffer rings

[Pavel Begunkov <asml.silence@gmail.com>]

On 2/12/26 10:07, Christoph Hellwig wrote:
> On Wed, Feb 11, 2026 at 02:06:18PM -0800, Joanne Koong wrote:
>>> I don't think I follow. I'm saying that it might be interesting
>>> to separate rings from how and with what they're populated on the
>>> kernel API level, but the fuse kernel module can do the population
>>
>> Oh okay, from your first message I (and I think christoph too) thought
>> what you were saying is that the user should be responsible for
>> allocating the buffers with complete ownership over them, and then
>> just pass those allocated to the kernel to use. But what you're saying
>> is that just use a different way for getting the kernel to allocate
>> the buffers (eg through the IORING_REGISTER_MEM_REGION interface). Am
>> I reading this correctly?
> 
> I'm arguing exactly against this.  For my use case I need a setup
> where the kernel controls the allocation fully and guarantees user
> processes can only read the memory but never write to it.  I'd love
> to be able to piggy back than onto your work.

IORING_REGISTER_MEM_REGION supports both types of allocations. It can
have a new registration flag for read-only, and then you either make
the bounce avoidance optional or reject binding fuse to unsupported
setups during init. Any arguments against that? I need to go over
Joanne's reply, but I don't see any contradiction in principal with
your use case.

-- 
Pavel Begunkov