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From: Christoph Hellwig <hch@lst.de>
To: Jan Kara <jack@suse.cz>
Cc: Christoph Hellwig <hch@lst.de>,
	Chris Mason <chris.mason@oracle.com>,
	Cesar Eduardo Barros <cesarb@cesarb.net>,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-kernel@vger.kernel.org, Jens Axboe <jaxboe@fusionio.com>,
	linux-btrfs@vger.kernel.org,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	linux-fsdevel@vger.kernel.org, stable@kernel.org,
	Jens Axboe <axboe@kernel.dk>,
	Micha?? Piotrowski <mkkp4x4@gmail.com>,
	Chuck Ebbert <cebbert@redhat.com>,
	kernel@lists.fedoraproject.org, linux-mtd@lists.infradead.org,
	David Woodhouse <dwmw2@infradead.org>
Subject: Re: Dirtiable inode bdi default != sb bdi btrfs
Date: Thu, 30 Sep 2010 02:06:41 +0200	[thread overview]
Message-ID: <20100930000641.GA27865@lst.de> (raw)
In-Reply-To: <20100929233806.GB12707@quack.suse.cz>

On Thu, Sep 30, 2010 at 01:38:07AM +0200, Jan Kara wrote:
> > No.  For one thing we don't need any exception for correctnes alone -
> > even the block device variant would work fine with the default case.
> Here I don't agree. If you don't have some kind of exception, sb->s_bdi
> for both "block" and "mtd_inodefs" filesystems points to
> noop_backing_dev_info and you get no writeback for that one. So it isn't
> just a performance issue but also a correctness one.

Indeed - for internal filesystems that require writeback the change
causes trouble if they haven't registered a s_bdi.  But for all user
visible filesystems that doesn't happen as we require s_bdi for
sync or even unmounts to work.

  reply	other threads:[~2010-09-30  0:06 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-09-23  0:54 Dirtiable inode bdi default != sb bdi btrfs Cesar Eduardo Barros
2010-09-23 19:38 ` Andrew Morton
2010-09-23 19:40   ` Chris Mason
2010-09-23 19:40   ` Jens Axboe
2010-09-23 20:53     ` [stable] " Greg KH
2010-09-24 18:39       ` Jens Axboe
2010-09-27  0:15         ` Greg KH
2010-09-27 22:25   ` Jan Kara
2010-09-27 22:54     ` Chris Mason
2010-09-27 23:51       ` Jan Kara
2010-09-28  7:05       ` Artem Bityutskiy
2010-09-29 13:00         ` Jan Kara
2010-09-29 13:40           ` Artem Bityutskiy
2010-09-29  8:19       ` Christoph Hellwig
     [not found]       ` <20100929081936.GA23322@lst.de>
     [not found]         ` <20100929081936.GA23322-jcswGhMUV9g@public.gmane.org>
2010-09-29 12:18           ` Jan Kara
2010-09-29 14:10             ` Christoph Hellwig
2010-09-29 23:38               ` Jan Kara
2010-09-30  0:06                 ` Christoph Hellwig [this message]
2010-09-27 23:55     ` Cesar Eduardo Barros
     [not found]       ` <4CA12F01.2-PWySMVKUnqmsTnJN9+BGXg@public.gmane.org>
2010-09-29 13:01         ` Jan Kara

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