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Subject: Re: [PATCH v2] fs: Add aio iopriority support for block_dev
To:     Adam Manzanares <Adam.Manzanares@wdc.com>,
        Matthew Wilcox <willy@infradead.org>
Cc:     "viro@zeniv.linux.org.uk" <viro@zeniv.linux.org.uk>,
        "bcrl@kvack.org" <bcrl@kvack.org>,
        "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
        "linux-aio@kvack.org" <linux-aio@kvack.org>,
        "linux-api@vger.kernel.org" <linux-api@vger.kernel.org>,
        "linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
References: <20180503182114.2797-1-adam.manzanares@wdc.com>
 <20180503183353.GC1562@bombadil.infradead.org>
 <47e0a519-37b4-f5e7-0616-8659d11c2b69@wdc.com>
From:   Jens Axboe <axboe@kernel.dk>
Message-ID: <18300bdb-a12f-0b6c-1317-6db3e4391d57@kernel.dk>
Date:   Thu, 3 May 2018 14:24:58 -0600
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On 5/3/18 2:15 PM, Adam Manzanares wrote:
> 
> 
> On 5/3/18 11:33 AM, Matthew Wilcox wrote:
>> On Thu, May 03, 2018 at 11:21:14AM -0700, adam.manzanares@wdc.com wrote:
>>> If we want to avoid bloating struct kiocb, I suggest we turn the private field
>>> into a union of the private and ki_ioprio field. It seems like the users of
>>> the private field all use it at a point where we can yank the priority from
>>> the kiocb before the private field is used. Comments and suggestions welcome.
>>
>> Or we could just make ki_hint a u8 or u16 ... seems unlikely we'll need
>> 32 bits of ki_hint.  (currently defined values are 1-5)
> 
> I like the approach of using a u16 for the ki_hint. I'll update and 
> resubmit.

It's intended to be a mask. If you do shrink it for now, then we need some
guard code to ensure it can always carry what it needs to.

-- 
Jens Axboe