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

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Message-ID: <Pine.LNX.4.44L0.1003171129200.1734-100000@iolanthe.rowland.org>
Date:	Wed, 17 Mar 2010 11:30:18 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Jens Axboe <jens.axboe@...cle.com>
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 Wed, 17 Mar 2010, Jens Axboe wrote:

> 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().

Ah, that's where it is!  Thanks very much.

Alan Stern

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