Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Message-ID: <59b4350b-db95-f771-c4a4-f3ce38b342f9@gmail.com>
Date:   Thu, 14 Oct 2021 10:35:00 +0100
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101
 Thunderbird/91.1.2
Subject: Re: [PATCH v2 2/3] block: don't hide inode from block_device users
Content-Language: en-US
To:     Christoph Hellwig <hch@infradead.org>
Cc:     Jens Axboe <axboe@kernel.dk>, linux-block@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <cover.1634115360.git.asml.silence@gmail.com>
 <2b8c84834a304871d78f91d4ebe153fac2192fd5.1634115360.git.asml.silence@gmail.com>
 <YWb6VgEjEZFexiV0@infradead.org>
 <194577df-0402-6e3c-3534-af289b5494e0@gmail.com>
 <YWe3QZD+g8MSoCtT@infradead.org>
From:   Pavel Begunkov <asml.silence@gmail.com>
In-Reply-To: <YWe3QZD+g8MSoCtT@infradead.org>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 10/14/21 05:51, Christoph Hellwig wrote:
> On Wed, Oct 13, 2021 at 07:44:20PM +0100, Pavel Begunkov wrote:
>> Mildly hot in io_uring w/o fixed files, but that's not peak perf,
>> but would also be great to get rid of bdev->bd_inode dereference,
>> e.g. lots of in fops.c.
>>
>> Are you going to just hid the dereference in helpers or kill it
>> with some offseting magic?
> 
> The only real hot path uses I found is the size (which you and Jens
> already seem to have moved to use something out of the inode for the
> fast path),  and maybe the blkbits for which we could do the same.
> 
> So basically the idea is to not touch the inode in the hot path,
> and use accessors helpers in bdev.c that could do the offsetof trick.

I see, sounds good

-- 
Pavel Begunkov