From: Jan Kara <jack@suse.cz>
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Jan Kara <jack@suse.cz>,
hch@lst.de, linux-fsdevel@vger.kernel.org,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 2/4] chardev: Increment cdev reference count when i_cdev references it
Date: Tue, 4 Nov 2014 16:55:43 +0100 [thread overview]
Message-ID: <20141104155543.GD21902@quack.suse.cz> (raw)
In-Reply-To: <20141104154030.GI7996@ZenIV.linux.org.uk>
On Tue 04-11-14 15:40:30, Al Viro wrote:
> On Tue, Nov 04, 2014 at 04:37:52PM +0100, Jan Kara wrote:
> > On Tue 04-11-14 14:46:11, Al Viro wrote:
> > > On Wed, Oct 22, 2014 at 10:14:11PM +0200, Jan Kara wrote:
> > > > Currently i_cdev reference to a character device isn't accounted in the
> > > > reference count of the character device. This then requires us to track
> > > > all references through a list of all inodes referencing a character
> > > > device which is somewhat clumsy and requires list_head in each inode in
> > > > the system.
> > > >
> > > > So make i_cdev a reference like any other.
> > >
> > > So no rmmod for you until an inode of character device node you had
> > > closed a while ago finally gets evicted from icache? Or am I misreading
> > > you?
> > Yes, this is a consequence of the change. I should have noted in the
> > changelog I guess.
>
> That consequence looks broken, IMO.
Hum, it already behaves for block devices that way (and noone complained
- but admittedly block devices tied to strange modules are less common than
character devices). Also rmmod isn't that common IMO, but I see your point
that it's unintuitive behavior.
Alternatively we could clear i_cdev when the inode isn't open anymore (and
thus doesn't hold any references to cdev). The downside is we have to
re-lookup the character device on the first inode open. Would such a
solution look acceptable to you?
Honza
--
Jan Kara <jack@suse.cz>
SUSE Labs, CR
next prev parent reply other threads:[~2014-11-04 15:55 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-22 20:14 [PATCH 0/4 v2] fs: Remove i_devices from struct inode Jan Kara
2014-10-22 20:14 ` [PATCH 1/4] blockdev: Don't use i_devices inode field Jan Kara
2014-11-04 9:42 ` Christoph Hellwig
2014-10-22 20:14 ` [PATCH 2/4] chardev: Increment cdev reference count when i_cdev references it Jan Kara
2014-11-04 9:52 ` Christoph Hellwig
2014-11-04 10:01 ` Jan Kara
2014-11-04 14:46 ` Al Viro
2014-11-04 15:37 ` Jan Kara
2014-11-04 15:40 ` Al Viro
2014-11-04 15:55 ` Jan Kara [this message]
2014-11-04 16:03 ` Al Viro
2014-11-05 16:54 ` Jan Kara
2014-10-22 20:14 ` [PATCH 3/4] chardev: Don't use i_devices inode field Jan Kara
2014-11-04 9:54 ` Christoph Hellwig
2014-10-22 20:14 ` [PATCH 4/4] fs: Remove i_devices list head Jan Kara
2014-11-04 9:55 ` Christoph Hellwig
2014-10-31 9:48 ` [PATCH 0/4 v2] fs: Remove i_devices from struct inode Jan Kara
2014-11-04 10:27 [PATCH 0/4 v3] " Jan Kara
2014-11-04 10:27 ` [PATCH 2/4] chardev: Increment cdev reference count when i_cdev references it Jan Kara
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