[linux-lvm] error mounting snapshot of ext3 filesystem

[Aran Cox]

Ok, I know that several discussions regarding snapshots have occurred in
the last month or two and I've tried to read every post from those
threads.  Nothing I read has helped me solve my problem.

Essentially, I can create a snapshot LV but I cannot mount it.

I have compiled 2.4.17 with the lvm101-rc4 patch created from the source
archive.  (I specified -with-kernel_dir appropriately.)  I tried to
apply to apply the VFS-lock patch but the kernel would not compile after
having done so.  (I wasn't sure if I needed this patch or not, but I
tried applying it anyway.)  It fails like so:


make[2]: Entering directory `/home/spin/src/linux/fs'
gcc -D__KERNEL__ -I/home/spin/src/linux/include -Wall
-Wstrict-prototypes -Wno-trigraphs -O2 -fomit-frame-pointer
-fno-strict-aliasing -fno-common -pipe -mpreferred-stack-boundary=2
-march=i686    -c -o super.o super.c
super.c: In function `unlockfs':
super.c:403: `mount_sem' undeclared (first use in this function)
super.c:403: (Each undeclared identifier is reported only once
super.c:403: for each function it appears in.)
make[2]: *** [super.o] Error 1


Anyway, continuing without VFS lock:
I have three disks, an IDE disk /dev/hda, and two small SCSI disk,
/dev/sda and /dev/sdb and one VG with /dev/hda4, and the entirety of
both SCSI disks in it which is called main. 

/boot 	/dev/hda3
/ 	/dev/main/root  (entirely on hda4)
/var	/dev/main/var	(entirely on hda4)
/tmp	/dev/main/scratch (on both sda and sdb)
/home	/dev/main/home  (spread out across all three PVs)

There are some PVs left on sdb, otherwise it's all used.
All of the filesystems are ext3, except /boot which is ext2.

This is basically the sequence of events:

[root at benway /]# lvcreate -s -n snaptest -L 200m /dev/main/root 
lvcreate -- WARNING: the snapshot will be automatically disabled once it
gets full
lvcreate -- INFO: using default snapshot chunk size of 64.00 KB for
"/dev/main/snaptest"
lvcreate -- doing automatic backup of "main"
lvcreate -- logical volume "/dev/main/snaptest" successfully created

[root at benway /]# mount /dev/main/snaptest /mnt
mount: block device /dev/main/snaptest is write-protected, mounting
read-only
mount: wrong fs type, bad option, bad superblock on /dev/main/snaptest,
       or too many mounted file systems

Trying to mount it as ext2 doesn't change anything.  No matter which LV
I create the snapshot of, I cannot mount it and it fails with the same
error.  

Even if I create a small LV with ext3 filesystem entirely on sdb, and
then create a snapshot of it, it still won't mount.  I can get this
small-all-on-one LV/FS scenario to work if I create an ext2 fs on the
LV.  

I know this is nearly exactly like the problems discussed in previous
threads but I haven't seen a solution yet that seems like it applied to
my situation.  

Thanks,
Aran
  


-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 232 bytes
Desc: This is a digitally signed message part
URL: <http://listman.redhat.com/archives/linux-lvm/attachments/20020122/d530c02e/attachment.sig>