On Tue, 24 Jun 2008 15:59:19 +0900 Takashi Sato <t-sato@xxxxxxxxxxxxx> wrote: > Hi Andrew and Alexander, > > I have implemented the ioctls for the filesystem freeze feature > and discussed its implementation on the ML (linux-ext4, xfs, > linux-fsdevel, linux-kernel) for five months. All of the comments are > addressed in my patch-set. > Could you consider merging it into Linux? > > The filesystem freeze feature can suspend accesses to the filesystem > keeping the filesystem's consistency. We can take the consistent backup > with it cooperating with the backup software. > > The patches are re-based from linux-2.6.26-rc3 to linux-2.6.26-rc7 > There is no functional change from the previous version. > The patch-set consists of the following three patches. > > [PATCH 1/3] Implement generic freeze feature > I have modified to set the suitable error number (EOPNOTSUPP) > in case the filesystem doesn't support the 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 2/3] Remove XFS specific ioctl interfaces for freeze feature > It removes XFS specific ioctl interfaces and request codes > for freeze feature. > This patch has been supplied by David Chinner. > > [PATCH 3/3] 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. umm, OK, but nowhere in this patch series can I find a justification or reason for making these changes to Linux. Why do we want to do this? What is the benefit? What is the motivation. What are the use-cases, etc? Thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
