linux-kernel - Re: [PATCH 3/7] block: push down BKL into .open and .release

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Date:	Thu, 08 Jul 2010 10:41:13 +0200
From:	Jens Axboe <axboe@...nel.dk>
To:	Arnd Bergmann <arnd@...db.de>
CC:	Christoph Hellwig <hch@...radead.org>,
	Sam Ravnborg <sam@...nborg.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 3/7] block: push down BKL into .open and .release

On 2010-07-07 16:51, Arnd Bergmann wrote:
> The open and release block_device_operations are currently
> called with the BKL held. In order to change that, we must
> first make sure that all drivers that currently rely
> on this have no regressions.
> 
> This blindly pushes the BKL into all .open and .release
> operations for all block drivers to prepare for the
> next step. The drivers can subsequently replace the BKL
> with their own locks or remove it completely when it can
> be shown that it is not needed.
> 
> The functions blkdev_get and blkdev_put are the only
> remaining users of the big kernel lock in the block
> layer, besides a few uses in the ioctl code, none
> of which need to serialize with blkdev_{get,put}.
> 
> Most of these two functions is also under the protection
> of bdev->bd_mutex, including the actual calls to
> ->open and ->release, and the common code does not
> access any global data structures that need the BKL.

This is missing an smp_lock.h include in i2o as well.
You seem to only add these sporadically, I think that
is a bit unsafe since you are relying on unknown
include hierarchies. That tends to break on one arch
or config even if it works in another.

-- 
Jens Axboe

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