Re: 21 million inodes is causing severe pauses.

[Andrew Morton <akpm@osdl.org>]

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().

> 
>  I guess I am really asking for an indication of what the BKL is supposed
>  to be protecting.  I have not dug for the intent down the VFS code paths
>  at all.

It's not protecting anything around invalidate_inodes().  There may be
other things in the higher-level umount path which need it.