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Message-ID: <3783abbf-2585-48fb-b04b-9206ade7f22d@kernel.dk>
Date: Fri, 4 Apr 2025 16:00:59 -0600
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Subject: Re: [PATCH 4/4] io_uring: reuse buffer updates for registration
To: Pavel Begunkov <asml.silence@gmail.com>, io-uring@vger.kernel.org
References: <cover.1743783348.git.asml.silence@gmail.com>
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From: Jens Axboe <axboe@kernel.dk>
In-Reply-To: <609ff085-34a2-4b3d-a984-57ab2f9fcad6@gmail.com>
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On 4/4/25 3:38 PM, Pavel Begunkov wrote:
> On 4/4/25 17:38, Jens Axboe wrote:
>> On 4/4/25 10:22 AM, Pavel Begunkov wrote:
>>> @@ -316,17 +318,26 @@ static int __io_sqe_buffers_update(struct io_ring_ctx *ctx,
>>> err = PTR_ERR(node);
>>> break;
>>> }
>>> - i = array_index_nospec(up->offset + done, ctx->buf_table.nr);
>>> - io_reset_rsrc_node(ctx, &ctx->buf_table, i);
>>> - ctx->buf_table.nodes[i] = node;
>>> + i = array_index_nospec(up->offset + done, buf_table->nr);
>>> + io_reset_rsrc_node(ctx, buf_table, i);
>>> + buf_table->nodes[i] = node;
>>> if (ctx->compat)
>>> user_data += sizeof(struct compat_iovec);
>>> else
>>> user_data += sizeof(struct iovec);
>>> }
>>> + if (last_error)
>>> + *last_error = err;
>>> return done ? done : err;
>>> }
>>> +static int __io_sqe_buffers_update(struct io_ring_ctx *ctx,
>>> + struct io_uring_rsrc_update2 *up,
>>> + unsigned int nr_args)
>>> +{
>>> + return io_buffer_table_update(ctx, &ctx->buf_table, up, nr_args, NULL);
>>> +}
>>
>> Minor style preference, but just do:
>>
>> unsigned last_err;
>> return io_buffer_table_update(ctx, &ctx->buf_table, up, nr_args, &last_err);
>>
>> and skip that last_error could be conditionally set?
>
> I can't say I see how that's better though
I think so though, it makes the store unconditional and there's no risk
of anything forgetting that last_error is sometimes valid, sometimes
not. The last part is the most annoying to me, it's just more fragile
imho.
--
Jens Axboe