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From: "Theodore Y. Ts'o" <tytso@mit.edu>
To: adam.manzanares@wdc.com
Cc: viro@zeniv.linux.org.uk, bcrl@kvack.org,
	linux-fsdevel@vger.kernel.org, linux-aio@kvack.org,
	linux-api@vger.kernel.org, linux-block@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 2/3] fs: Convert kiocb rw_hint from enum to u16
Date: Wed, 9 May 2018 09:34:32 -0400	[thread overview]
Message-ID: <20180509133432.GD28388@thunk.org> (raw)
In-Reply-To: <20180508174202.2537-3-adam.manzanares@wdc.com>

On Tue, May 08, 2018 at 10:42:01AM -0700, adam.manzanares@wdc.com wrote:
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 760d8da1b6c7..7a90ce387e00 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -284,6 +284,8 @@ enum rw_hint {
>  	WRITE_LIFE_EXTREME	= RWH_WRITE_LIFE_EXTREME,
>  };
>  
> +#define MAX_KI_HINT		((1 << 16) - 1) /* ki_hint type is u16 */
> +

Do we really think there will be *ever* be a need for more than 16 I/O
priority levels?  I would much rather use the low four bits of KI_HINT
for the priority level, and reserve the rest of the 16 bits in KI_HINT
for some future use.  (For example, we might want to use some number
of bits for a stream ID.)

					- Ted

  reply	other threads:[~2018-05-09 13:34 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-08 17:41 [PATCH v3 0/3] AIO add per-command iopriority adam.manzanares
2018-05-08 17:42 ` [PATCH v3 1/3] block: add ioprio_check_cap function adam.manzanares
2018-05-08 17:42 ` [PATCH v3 2/3] fs: Convert kiocb rw_hint from enum to u16 adam.manzanares
2018-05-09 13:34   ` Theodore Y. Ts'o [this message]
2018-05-09 14:23     ` Jens Axboe
2018-05-09 15:21       ` Theodore Y. Ts'o
2018-05-09 15:29         ` Adam Manzanares
2018-05-08 17:42 ` [PATCH v3 3/3] fs: Add aio iopriority support for block_dev adam.manzanares
2018-05-09  8:54   ` kbuild test robot

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