linux-kernel - Re: [PATCH] Cleanup: Remove unused __REQ_NR_BITS from enum rq_flag

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Date:	Mon, 27 Apr 2009 13:46:33 +0200
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Nikanth Karthikesan <knikanth@...e.de>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Cleanup: Remove unused __REQ_NR_BITS from enum
	rq_flag_bits

On Mon, Apr 27 2009, Nikanth Karthikesan wrote:
> The __REQ_NR_BITS  was being used by blk_dump_rq_flags() long back, while 
> printing the individual request flag bits as strings to limit to the used 
> bits. But it does not use it now. Remove unused enum.
> 
> Signed-off-by: Nikanth Karthikesan <knikanth@...e.de>
> 
> ---
> 
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index ba54c83..f41abbb 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -118,7 +118,6 @@ enum rq_flag_bits {
>  	__REQ_COPY_USER,	/* contains copies of user pages */
>  	__REQ_INTEGRITY,	/* integrity metadata has been remapped */
>  	__REQ_NOIDLE,		/* Don't anticipate more IO after this one */
> -	__REQ_NR_BITS,		/* stops here */
>  };
>  
>  #define REQ_RW		(1 << __REQ_RW)

Lets turn it into something useful instead. It's meant to catch someone
adding too many flags, how about something like this:

Untested ;-)

diff --git a/block/blk-core.c b/block/blk-core.c
index d73eb76..e62ef94 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -2159,6 +2159,8 @@ EXPORT_SYMBOL(kblockd_schedule_work);
 
 int __init blk_dev_init(void)
 {
+	BUILD_BUG_ON(__REQ_NR_BITS > 8 * sizeof(int));
+
 	kblockd_workqueue = create_workqueue("kblockd");
 	if (!kblockd_workqueue)
 		panic("Failed to create kblockd\n");

-- 
Jens Axboe

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