Re: 21 million inodes is causing severe pauses.

[Robin Holt <holt@sgi.com>]

On Tue, Nov 16, 2004 at 11:13:21AM -0800, Andrew Morton wrote:
> Robin Holt <holt@sgi.com> wrote:
> >
> > I guess I am very concerned at this point.  If I can do a
> >  release/reacquire, why not just change generic_shutdown_super() so the
> >  lock_kernel() does not happen until the first pass has occurred.  ie:
> > 
> >  --- super.c.orig        2004-11-16 10:22:17 -06:00
> >  +++ super.c     2004-11-16 10:22:41 -06:00
> >  @@ -232,10 +232,10 @@
> >                  dput(root);
> >                  fsync_super(sb);
> >                  lock_super(sb);
> >  -               lock_kernel();
> >                  sb->s_flags &= ~MS_ACTIVE;
> >                  /* bad name - it should be evict_inodes() */
> >                  invalidate_inodes(sb);
> >  +               lock_kernel();
> > 
> >                  if (sop->write_super && sb->s_dirt)
> >                          sop->write_super(sb);
> > 
> >  This at least makes the lock_kernel time much smaller than it is right
> >  now.  It also does not affect any callers that may really need the BKL.
> 
> lock_kernel() is also taken way up in do_umount(), hence the need for
> release_kernel_lock()/reacquire_kernel_lock().

It looks like it is only held very briefly during the early parts of do_umount.

I have moved lock_kernel() as above in addition to the two patches you pointed
to earlier.  This has left me with a system which has 21M inodes and undetectable
delays during heavy mount/umount activity.  I am starting one last test which
attempts a umount of a filesystem which has many inodes associated with it.

At this point, I have checked the entire code path and see no reason the
BKL is held for the first call to invalidate_inodes.