linux-kernel - Re: Block device files and the page cache

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Message-ID: <20100317102252.GT5768@kernel.dk>
Date:	Wed, 17 Mar 2010 11:22:52 +0100
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Alexander Viro <viro@...iv.linux.org.uk>,
	linux-fsdevel@...r.kernel.org,
	Kernel development list <linux-kernel@...r.kernel.org>
Subject: Re: Block device files and the page cache

On Tue, Mar 16 2010, Alan Stern wrote:
> Jens and Al:
> 
> Simple testing seems to show that when a program closes a file
> descriptor for a block device file, the release method in the device
> driver's block_device_operations structure doesn't get called (and the
> close(2) system call doesn't return) until all the dirty pages for that 
> device have been written out.
> 
> Can anyone confirm that this always happens?  Where in the kernel 
> source is this handled?

Alan, see fs/block_dev.c:__blkdev_put(). The last put of the device will
sync the device before calling fops->release().

-- 
Jens Axboe

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