Re: Add a norecovery option to ext3/4?

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Mon, 9 April 2007 12:21:15 -0500, Eric Sandeen wrote:
> Phillip Susi wrote:
> > 
> > When the filesystem is told to mount the disk read only, that means it 
> > should not write to it.  
> 
> It means the filesystem should not be writeable when it is mounted.
> This is not the same as saying that the filesystem itself should do no
> IO in the course of making that read-only mount available.

The filesystem has two interfaces.  One to the device underneith, one to
userspace.  Read-only should certainly mean that no writes cross the
userspace interface.  Traditionally it has implicitly also meant that
no writes are crossing the device interface.  Whether that was/is an
explicit requirement - who knows.

Journaling filesystems have introduced this thing called "journal
replay".  And I have to admit, it makes thing _a lot_ easier to always
replay the journal, even when being mounted read-only.

But "it is easier" is a pretty lame excuse.

> Under all conditions it should be safe to mount a read-only block
> device, but that is not the same as mounting a filesystem read-only.

In particular, it is a lame excuse when this claim is true.  If the
block-device is read-only, then journal replay will not work as expected
and all the "not so easy" work has to be done anyway.

Did I miss anything?  Is it actually easier to mount a read-only device
with unclean journal than mounting a read-write device and not replay
the journal?

Jörn

-- 
Joern's library part 8:
http://citeseer.ist.psu.edu/plank97tutorial.html
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

[Index of Archives]     [Kernel Newbies]     [Netfilter]     [Bugtraq]     [Photo]     [Stuff]     [Gimp]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Video 4 Linux]     [Linux for the blind]     [Linux Resources]
  Powered by Linux