linux-kernel - Re: [PATCH v2 2/3] block: don't hide inode from block

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Message-ID: <59b4350b-db95-f771-c4a4-f3ce38b342f9@gmail.com>
Date:   Thu, 14 Oct 2021 10:35:00 +0100
From:   Pavel Begunkov <asml.silence@...il.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Jens Axboe <axboe@...nel.dk>, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/3] block: don't hide inode from block_device users

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