On Mon, Sep 03, 2007 at 08:59:02AM +0200, Jan Engelhardt wrote:
>
> On Sep 2 2007 22:20, Josef 'Jeff' Sipek wrote:
> >+
> >+While rebuilding Unionfs's objects, we also purge any page mappings and
> >+truncate inode pages (see fs/Unionfs/dentry.c:purge_inode_data). This is to
>
> fs/unionfs/dentry.c
>
> >+Unionfs maintains the following important invariant regarding mtime's,
> >+ctime's, and atime's: the upper inode object's times are the max() of all of
>
> utimes, ctimes and atimes.
>
> >+2. Lockdep (a debugging feature) isn't aware of stacking, and so it
> >+ incorrectly complains about locking problems. The problem boils down to
> >+ this: Lockdep considers all objects of a certain type to be in the same
> >+ class, for example, all inodes. Lockdep doesn't like to see a lock held
> >+ on two inodes within the same task, and warns that it could lead to a
> >+ deadlock. However, stackable file systems do precisely that: they lock
> >+ an upper object, and then a lower object, in a strict order to avoid
> >+ locking problems; in addition, Unionfs, as a fan-out file system, may
> >+ have to lock several lower inodes. We are currently looking into Lockdep
> >+ to see how to make it aware of stackable file systems. In the mean time,
>
> meantime
>
> >@@ -86,5 +86,12 @@ command:
> >
> > # mount -t unionfs -o remount,incgen none MOUNTPOINT
> >
> >+Note that the older way of incrementing the generation number using an
> >+ioctl, is no longer supported in Unionfs 2.0. Ioctls in general are not
>
> 2.1?
Thanks.
Jeff.
--
Penguin : Linux version 2.4.20-46.9.legacysmp on an i386 machine (2778.72 BogoMips).
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