linux-kernel - Re: [PATCH 5/6] block: remove BKL from partition code

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Date:	Tue, 6 Jul 2010 22:04:25 -0400
From:	Christoph Hellwig <hch@...radead.org>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Jens Axboe <axboe@...nel.dk>,
	Christoph Hellwig <hch@...radead.org>,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	John Kacur <jkacur@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	linux-scsi@...r.kernel.org
Subject: Re: [PATCH 5/6] block: remove BKL from partition code

On Sat, Jul 03, 2010 at 11:47:19PM +0200, Arnd Bergmann wrote:
> I don't see any reason why we need the BKL here.
> The functions blkdev_get, blkdev_put, blkpg_ioctl
> and blkdev_reread_part are the only remaining users
> of the big kernel lock in the block layer, and they
> all access the same fields of the bdev and gendisk
> structures, yet they always do so under the protection
> of bdev->bd_mutex.
> 
> The open and close block_device_operations have all
> been converted to grab the BKL themselves, where
> necessary, so as far I can tell it should be safe
> to remove.

The content of the patch really does not match the subject at all,
which is a rather bad thing.

Anyway, dropping from blkdev_reread_part and blkpg_ioctl is easy
enough, and fine from a quick audit of the functions.

Dropping it from blkdev_get/put also seems fine from a quick
glance.  But that should be part of pushing the BKL into
->open/release.

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