Re: Strange remount behaviour with ext3-2.4-0.9.4

Alan Cox
2001-07-27T20:46:06Z

> Regardless of possible weirdness in a "smart" behaviour of 'mount' what
> one exactly buys running a journaling file system on a _read only_
> partition? fsck times will be the same (unless you crashed when
> installing new software :-).

Several things:

1. The simple case of remounting an fs read-only is easy, since no
writes means no journal

2. The software suspend case is horrible. Right now mixing a
journalling fs and swsuspend tends to cause disk corruption because
journalling fs's write to disk when told to mount read only

3. Failed drives. Here the journalling mount overrides the read only
request and the machine locks up preventing data recovery except
by copying the whole 80Gb disk image to another disk

Been there, it sucks

4. Snapshots. Making read only snapshots can be very useful, and there
you want the replay of the log to be into the page cache but not
written back to physical media until its marked read-write

Alan