Hi, Andrew, Christoph and Oleg
I've addressed your comments in these patches
and re-based from linux-2.6.26-rc3 to linux-2.6.27-rc5.
The points are followings.
- Replaced the semaphore (bd_freeze_sem) with
the mutex (bd_fsfreeze_mutex).
- To avoid the deadlock, fixed thaw_bdev() so that it didn't call
del_freeze_timeout() only when it's called by the delayed work task.
- Changed the function names and global symbol names like
xxx_freeze_yyy() to xxx_fsfreeze_yyy().
- Removed unnecessary EXPORT_SYMBOL_GPL.
- Fixed some comments and changelogs properly.
Please refer to following my previous mails for details of changes.
- http://marc.info/?l=linux-ext4&m=122000280524578&w=2
- http://marc.info/?l=linux-ext4&m=122000280424572&w=2
- http://marc.info/?l=linux-ext4&m=122000293824805&w=2
Currently, ext3 in mainline Linux doesn't have the freeze feature which
suspends write requests. So, we cannot take a backup which keeps
the filesystem's consistency with the storage device's features
(snapshot and replication) while it is mounted.
In many case, a commercial filesystem (e.g. VxFS) has
the freeze feature and it would be used to get the consistent backup.
If Linux's standard filesytem ext3 has the freeze feature, we can do it
without a commercial filesystem.
So I have implemented the ioctls of the freeze feature.
I think we can take the consistent backup with the following steps.
1. Freeze the filesystem with the freeze ioctl.
2. Separate the replication volume or create the snapshot
with the storage device's feature.
3. Unfreeze the filesystem with the unfreeze ioctl.
4. Take the backup from the separated replication volume
or the snapshot.
[PATCH 1/3] 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 ...
