linux-kernel - FIFREEZE guarantees

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Date:	Tue, 27 Jan 2009 10:46:34 +0100
From:	linux-kernel-owner@...r.kernel.org
To:	lkml@...r.kernel.org, Takashi Sato <t-sato@...jp.nec.com>
Subject: FIFREEZE guarantees

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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