On Mon, Mar 24, 2008 at 08:11:36PM +0900, Takashi Sato wrote: > Hi, > > This is the rebased freeze feature patch for linux-2.6.25-rc6. > We can take a backup which keeps the filesystem's consistency with it. > I have tested it cooperating with > DRBD (Distributed Replicated Block Device (http://www.drbd.org/)) > and made sure that I could take the consistent backup with a short > frozen time (several seconds) while using the filesystem. > The detailed procedure for my test is below. > > 1. Set up the replication between server A (primary) and > server B (secondary) > > 2. Make the ext3 filesystem on server A and mount it > (Run Linux kernel compile by 5 threads in parallel on it) > > 3. Freeze the filesystem on server A to block I/O and > keep the filesystem's consistency > > 4. Detach the secondary volume on server B > (e.g /sbin/drbdadm detach r0) > > 5. Unfreeze the filesystem on server A > > 6. Use the secondary volume on server B > I confirmed the followings. > - fsck didn't report any errors. > - It could be mounted correctly. > - Linux kernel compiles could re-start correctly. > > There is no functional change from the previous version. > All of comments from ML have already been reflected in this patch. 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. I think this timeout stuff is dangerous - it adds significant complexity and really does not protect against anything that can't be done in userspace. i.e. If your system is running well enough for the timer to fire and unfreeze the filesystem, it's running well enough for you to do "freeze X; sleep Y; unfreeze X". If you are trying to protect against a freeze operation that hangs then the filesystem needs fixing, not some new API to work around a bug.... FWIW, there is nothing to guarantee that the filesystem has finished freezing when the timeout fires (it's not uncommon to see freeze_bdev() taking *minutes*) and unfreezing in the middle of a freeze operation will cause problems - either for the filesystem in the middle of a freeze operation, or for whatever is freezing the filesystem to get a consistent image..... Cheers, Dave. -- Dave Chinner Principal Engineer SGI Australian Software Group -- 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
