From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Chinner Subject: Re: [RFC] ext3 freeze feature Date: Sat, 26 Jan 2008 16:39:28 +1100 Message-ID: <20080126053928.GO155407@sgi.com> References: <20080125195938t-sato@mail.jp.nec.com> <20080126053526.GN155407@sgi.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Takashi Sato , linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org To: David Chinner Return-path: Content-Disposition: inline In-Reply-To: <20080126053526.GN155407@sgi.com> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On Sat, Jan 26, 2008 at 04:35:26PM +1100, David Chinner wrote: > On Fri, Jan 25, 2008 at 07:59:38PM +0900, Takashi Sato wrote: > > The points of the implementation are followings. > > - Add calls of the freeze function (freeze_bdev) and > > the unfreeze function (thaw_bdev) in ext3_ioctl(). > > > > - ext3_freeze_timeout() which calls the unfreeze function (thaw_bdev) > > is registered to the delayed work queue to unfreeze the filesystem > > automatically after the lapse of the specified time. > > Seems like pointless complexity to me - what happens if a > timeout occurs while the filsystem is still freezing? > > It's not uncommon for a freeze to take minutes if memory > is full of dirty data that needs to be flushed out, esp. if > dm-snap is doing COWs for every write issued.... Sorry, ignore this bit - I just realised the timer is set up after the freeze has occurred.... Still, that makes it potentially dangerous to whatever is being done while the filesystem is frozen.... Cheers, Dave. -- Dave Chinner Principal Engineer SGI Australian Software Group