On Wed 30-11-11 01:52:22, Mikulas Patocka wrote: > > > dm-ioctl.h: > > > /* > > > * Set this to avoid attempting to freeze any filesystem when suspending. > > > */ > > > #define DM_SKIP_LOCKFS_FLAG (1 << 10) /* In */ > > Thanks. I was now checking in detail and indeed FIFREEZE fails if > > ->freeze_fs is not set. And only xfs, ext3, ext4, reiserfs, jfs, nilfs2, > > and gfs2 provide this function. So I was correct in assuming that when > > filesystem supports FIFREEZE it must make sure no modifications happen to > > the filesystem. So I believe that my original plan for sync to skip frozen > > filesystem is correct. > > > > Honza > > LVM doesn't suspend with FIFREEZE, it calls freeze_bdev directly from > drivers/md/dm.c (and it works for all filesystems, including ext2). Ah, I see. Sorry I missed this. But then I can only reiterate that drivers/md/dm.c is IMHO broken. Either it cares about filesystem being really frozen - and then it should refuse the operation for e.g. ext2 because it cannot be frozen - or it does not care about filesystem being frozen and then there's no point in calling freeze_super(). Possibly, you might still want to e.g. try snapshotting even if freeze_super() would return EOPNOTSUPP but that should be handled inside dm, not by errorneously marking filesystem as frozen when it is not. Or am I still missing something? > So if you skip sync of frozen filesystems, you introduce a data > corruption if someone takes a snapshot of ext2. Yes, because ext2 cannot really be frozen, it is (errorneously) marked as such but it is not frozen... Honza -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
