Re: [linux-lvm] snapshot of Reiserfs

[Andreas Dilger <adilger@turbolinux.com>]

Chris, you write:
> On Wednesday, February 21, 2001 09:44:39 AM -0700 Andreas Dilger
> <adilger@turbolinux.com> wrote:
> > Given that the VFS support for the *unlockfs methods is included in 2.4.1,
> > this should probably become something like:
> > 
> > /* lvm_do_lv_create calls fsync_dev_lockfs()/unlockfs() */
> > #if LINUX_KERNEL_VERSION >= KERNEL_VERSION(2,4,1)
> > #define     LVM_VFS_ENHANCEMENT
> > #else
> > /* Need to apply a kernel patch to add lockfs/unlockfs VFS methods */
> > /* #define  LVM_VFS_ENHANCEMENT */
> > #endif
> > 
> 
> I like this idea.

Note that I thought the fsync_dev_lockfs() code was added to 2.4.1 when
reiserfs was added.  However, it appears that only the *lockfs pointers
were added to the super_operations, and the actual code that uses them
was NOT added.  This means we can't do the above until fsync_dev_lockfs()
is actually there.

> > Also, if the sync_supers_lockfs() method is changed to call write_super()
> > if write_super_lockfs() doesn't exist, like:
> 
> The fsync_dev_lockfs call does this for us, if there is no
> write_super_lockfs provided, fsync_dev_lockfs is effectively the same as
> calling fsync_dev.

Except that fsync_dev() calls the write_super() method, and fsync_dev_lockfs()
only calls the write_super_lockfs() method if it exists - it does not call
write_super() if write_super_lockfs() does not exist.  If it were changed as
I suggest, then the two would be the same.

Cheers, Andreas
-- 
Andreas Dilger  \ "If a man ate a pound of pasta and a pound of antipasto,
                 \  would they cancel out, leaving him still hungry?"
http://www-mddsp.enel.ucalgary.ca/People/adilger/               -- Dogbert