From: Takashi Sato Subject: [RFC PATCH 0/2] freeze feature ver 1.0 Date: Fri, 28 Mar 2008 18:02:24 +0900 Message-ID: <20080328180224t-sato@mail.jp.nec.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: "linux-fsdevel@vger.kernel.org" , "linux-ext4@vger.kernel.org" , "xfs@oss.sgi.com" , "dm-devel@redhat.com" , "linux-kernel@vger.kernel.org" To: David Chinner Return-path: Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org Hi, David Chinner wrote: > Can you please split this into two patches - one which introduces the > generic functionality *without* the timeout stuff, and a second patch > that introduces the timeouts. OK. I split my patch into two patches as below. [PATCH 1/2] Implement generic freeze feature The ioctls for the generic freeze feature are below. o Freeze the filesystem int ioctl(int fd, int FIFREEZE, arg) fd: The file descriptor of the mountpoint FIFREEZE: request code for the freeze arg: Ignored Return value: 0 if the operation succeeds. Otherwise, -1 o Unfreeze the filesystem int ioctl(int fd, int FITHAW, arg) fd: The file descriptor of the mountpoint FITHAW: request code for unfreeze arg: Ignored Return value: 0 if the operation succeeds. Otherwise, -1 [PATCH 2/2] Add timeout feature The timeout feature is added to freeze ioctl. And new ioctl to reset the timeout period is added. o Freeze the filesystem int ioctl(int fd, int FIFREEZE, long *timeval) fd: The file descriptor of the mountpoint FIFREEZE: request code for the freeze timeval: the timeout period in seconds If it's 0 or 1, the timeout isn't set. This special case of "1" is implemented to keep the compatibility with XFS applications. Return value: 0 if the operation succeeds. Otherwise, -1 o Reset the timeout period This is useful for the application to set the timeval more accurately. For example, the freezer resets the timeval to 10 seconds every 5 seconds. In this approach, even if the freezer causes a deadlock by accessing the frozen filesystem, it will be solved by the timeout in 10 seconds and the freezer can recognize that at the next reset of timeval. int ioctl(int fd, int FIFREEZE_RESET_TIMEOUT, long *timeval) fd:file descriptor of mountpoint FIFREEZE_RESET_TIMEOUT: request code for reset of timeout period timeval: new timeout period in seconds Return value: 0 if the operation succeeds. Otherwise, -1 Error number: If the filesystem has already been unfrozen, errno is set to EINVAL. Any comments are very welcome. Cheers, Takashi