FIFREEZE guarantees

From: linux-kernel-owner
Date: Tue Jan 27 2009 - 05:43:10 EST


Hi,
I'm confused about what 'freezing' a filesystem with FIFREEZE is
supposed to do. I thought that it roughly the same a sync, that is the
snapshot of filesystem taken between FIFREEZE and FITHAW should be error
free.

It doesn't seem to work this way:
(I have ext3 filesystem on a LVM volume, mounted on /)
./fifreeze / (this just makes the FIFREEZE ioctl)
lvcreate -L 20642428k -n root_fscksnap -s /dev/system/root
Rounding up size to full physical extent 19.69 GB
Logical volume "root_fscksnap" created
./fithaw / (this just makes the FITHAW ioctl)
fsck.ext3 -f -n /dev/system/root_fscksnap -v -C0
e2fsck 1.41.1 (01-Sep-2008)
Pass 1: Checking inodes, blocks, and sizes
Inodes that were part of a corrupted orphan linked list found. Fix? no
Inode 460301 was part of the orphaned inode list. IGNORED.
...
Deleted inode 615223 has zero dtime. Fix? no
...
/dev/system/root_fscksnap: ********** WARNING: Filesystem still has errors **********

Mounting the snapshot, however, allows the fsck to proceed without error:
./fifreeze /
lvcreate -L 20642428k -n root_fscksnap -s /dev/system/root
./fithaw /
mount -v -t ext3 /dev/system/root_fscksnap /dev/shm/fsmount.cP2A2a
/dev/mapper/system-root_fscksnap on /dev/shm/fsmount.cP2A2a type ext3 (rw)
umount -v /dev/shm/fsmount.cP2A2a
/dev/mapper/system-root_fscksnap umounted
fsck.ext3 -f -n /dev/system/root_fscksnap -v -C0
... file system clean ...

Looking for some enlightment,
Zbyszek

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