linux-kernel - Re: [RFC PATCH v2 0/2] introduce io_uring_cmd_import_fixed

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Message-ID: <ab277f0b-fdf6-4f20-9fe0-0e0a1ebcc906@kernel.dk>
Date: Thu, 13 Mar 2025 08:01:15 -0600
From: Jens Axboe <axboe@...nel.dk>
To: Sidong Yang <sidong.yang@...iosa.ai>,
 Pavel Begunkov <asml.silence@...il.com>
Cc: Josef Bacik <josef@...icpanda.com>, David Sterba <dsterba@...e.com>,
 linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org,
 io-uring@...r.kernel.org
Subject: Re: [RFC PATCH v2 0/2] introduce io_uring_cmd_import_fixed_vec

On 3/13/25 7:56 AM, Sidong Yang wrote:
> On Thu, Mar 13, 2025 at 01:17:44PM +0000, Pavel Begunkov wrote:
>> On 3/13/25 13:15, Pavel Begunkov wrote:
>>> On 3/13/25 10:44, Sidong Yang wrote:
>>>> On Thu, Mar 13, 2025 at 08:57:45AM +0000, Pavel Begunkov wrote:
>>>>> On 3/12/25 14:23, Sidong Yang wrote:
>>>>>> This patche series introduce io_uring_cmd_import_vec. With this function,
>>>>>> Multiple fixed buffer could be used in uring cmd. It's vectored version
>>>>>> for io_uring_cmd_import_fixed(). Also this patch series includes a usage
>>>>>> for new api for encoded read in btrfs by using uring cmd.
>>>>>
>>>>> Pretty much same thing, we're still left with 2 allocations in the
>>>>> hot path. What I think we can do here is to add caching on the
>>>>> io_uring side as we do with rw / net, but that would be invisible
>>>>> for cmd drivers. And that cache can be reused for normal iovec imports.
>>>>>
>>>>> https://github.com/isilence/linux.git regvec-import-cmd
>>>>> (link for convenience)
>>>>> https://github.com/isilence/linux/tree/regvec-import-cmd
>>>>>
>>>>> Not really target tested, no btrfs, not any other user, just an idea.
>>>>> There are 4 patches, but the top 3 are of interest.
>>>>
>>>> Thanks, I justed checked the commits now. I think cache is good to resolve
>>>> this without allocation if cache hit. Let me reimpl this idea and test it
>>>> for btrfs.
>>>
>>> Sure, you can just base on top of that branch, hashes might be
>>> different but it's identical to the base it should be on. Your
>>> v2 didn't have some more recent merged patches.
>>
>> Jens' for-6.15/io_uring-reg-vec specifically, but for-next likely
>> has it merged.
> 
> Yes, there is commits about io_uring-reg-vec in Jens' for-next. I'll
> make v3 based on the branch.

Basing patches on that is fine, just never base branches on it. My
for-next branch is just a merge point for _everything_ that's queued for
the next release, io_uring and block related. The right branch to base
on for this case would be for-6.15/io_uring-reg-vec, which is also in my
for-next branch.

This is more of a FYI than anything, as you're not doing a pull request.
Using for-next for patches is fine.

-- 
Jens Axboe