Comment 23 for bug 41624

Revision history for this message
Ian Jackson (ijackson) wrote : Re: [Bug 41624] Re: Replaying journals of other OS's filesystems, by mounting them, is unsafe

Phillip Susi writes ("[Bug 41624] Re: Replaying journals of other OS's filesystems, by mounting them, is unsafe"):
> Which kernel you are using does not really matter because the linux
> kernel developers consider this to be working as intended. I have tried
> arguing with the on the LKML a few times with no success. They seem to
> think that the read only mount flag does not mean "do not write to this
> disk" but rather "do not allow files to be opened for write access".

Phillip is correct.

> If we want this fixed, we're going to have to fix it ourselves it looks
> like.

I think we should do so.

Just this week I was helping someone recover a machine which was
already damaged at the time and was made worse when they typed
   mount -o ro /dev/mapper/volumegroup-logicalvolume-real /mnt
which causes ext3 to write the journal back into the snapshotted
volume bypassing the LVM system.

You can say "don't do that then" but
   mount -o ro
is exactly what every administrator reaches for in time of trouble,
and they expect it to do no harm.

Ian.