linux-kernel - Re: [PATCH v2] fs: Add aio iopriority support for block

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Date:   Thu, 3 May 2018 15:43:08 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     Adam Manzanares <Adam.Manzanares@....com>,
        "viro@...iv.linux.org.uk" <viro@...iv.linux.org.uk>,
        "bcrl@...ck.org" <bcrl@...ck.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linux-aio@...ck.org" <linux-aio@...ck.org>,
        "linux-api@...r.kernel.org" <linux-api@...r.kernel.org>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] fs: Add aio iopriority support for block_dev

On Thu, May 03, 2018 at 02:24:58PM -0600, Jens Axboe wrote:
> On 5/3/18 2:15 PM, Adam Manzanares wrote:
> > On 5/3/18 11:33 AM, Matthew Wilcox wrote:
> >> 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.

ummm ...

enum rw_hint {
        WRITE_LIFE_NOT_SET      = 0,
        WRITE_LIFE_NONE         = RWH_WRITE_LIFE_NONE,
        WRITE_LIFE_SHORT        = RWH_WRITE_LIFE_SHORT,
...

                .ki_hint = file_write_hint(filp),

static inline enum rw_hint file_write_hint(struct file *file)

#define RWF_WRITE_LIFE_NOT_SET  0
#define RWH_WRITE_LIFE_NONE     1
#define RWH_WRITE_LIFE_SHORT    2
#define RWH_WRITE_LIFE_MEDIUM   3
#define RWH_WRITE_LIFE_LONG     4
#define RWH_WRITE_LIFE_EXTREME  5

It doesn't look like it's being used as a mask.