linux-kernel - Re: block: DMA alignment of IO buffer allocated from slab

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Message-ID: <1a5b255f-682e-783a-7f99-9d02e39c4af2@kernel.dk>
Date:   Mon, 24 Sep 2018 12:09:37 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Christopher Lameter <cl@...ux.com>
Cc:     Christoph Hellwig <hch@....de>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Ming Lei <tom.leiming@...il.com>,
        linux-block <linux-block@...r.kernel.org>,
        linux-mm <linux-mm@...ck.org>,
        Linux FS Devel <linux-fsdevel@...r.kernel.org>,
        "open list:XFS FILESYSTEM" <linux-xfs@...r.kernel.org>,
        Dave Chinner <dchinner@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Ming Lei <ming.lei@...hat.com>
Subject: Re: block: DMA alignment of IO buffer allocated from slab

On 9/24/18 12:00 PM, Christopher Lameter wrote:
> On Mon, 24 Sep 2018, Jens Axboe wrote:
> 
>> The situation is making me a little uncomfortable, though. If we export
>> such a setting, we really should be honoring it...
> 
> Various subsystems create custom slab arrays with their particular
> alignment requirement for these allocations.

Oh yeah, I think the solution is basic enough for XFS, for instance.
They just have to error on the side of being cautious, by going full
sector alignment for memory...

-- 
Jens Axboe