Subject: Re: FFS journal
To: Manuel Bouyer <>
From: Magnus Eriksson <>
List: tech-kern
Date: 07/07/2006 13:33:04
(I'm just picking one mail at random to reply to here..)

On Wed, 5 Jul 2006, Manuel Bouyer wrote:

>> No, it should not be in fsck.  What if you want to mount a file
>> system read-only?

> If I mount a filesystem read-only I don't want anything to write to
> disk, dammit ! not even journal recovery.

   Perhaps one of you wizards could tell me what it is that makes it 
absolutely true that "replaying the journal" == "writing to disk".  I just 
don't see the connection.

   Shouldn't it be possible to chug through as much as is needed to get the 
filesystem into a consistent state (or even the entire journal) and just 
cache the result?

  (Yes, obviously there will be cases where it is not possible, on those 
bajillion jiggabytes filesystems that see lots of traffic.  That doesn't 
make it useless to have the option to at least *try*, does it?)

   And that sort of "virtual replay" might even be useful, even if I don't 
really know enough to pick a great example. (undeleting?)

   Anyway, I'm "just a user", so take this for what it is.  But if there's 
a simple answer, I'd like to hear it.