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SubjectRe: 21 million inodes is causing severe pauses.
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.

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