linux-kernel - Re: Possible fix for lockup in drop

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Message-ID: <532480950801081317y324ed146p25f08ed50ffd1911@mail.gmail.com>
Date:	Tue, 8 Jan 2008 13:17:42 -0800
From:	"Michael Rubin" <mrubin@...gle.com>
To:	"Andrew Morton" <akpm@...ux-foundation.org>
Cc:	richard <richard@....demon.co.uk>, den@...nvz.org,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: Possible fix for lockup in drop_caches

On Dec 22, 2007 2:06 AM, Andrew Morton <akpm@...ux-foundation.org> wrote:
> Oh boy.  Do we really want to add all this stuff to JBD just for
> drop_caches which is a silly root-only broken-in-22-other-ways thing?
>
> Michael, might your convert-inode-lists-to-tree patches eliminate the need
> for taking inode_lock in drop_pagecache_sb()?  Probably not, as it uses an
> rbtree.  It would have been possible if it was using a radix-tree, I
> suspect..

You are correct. The rbtree will still req
>
> > -void __journal_unfile_buffer(struct journal_head *jh)
> > +void __journal_unfile_buffer(struct journal_head *jh,
> > +             struct buffer_head **dirty_bh)
> >  {
> > -     __journal_temp_unlink_buffer(jh);
> > +     __journal_temp_unlink_buffer(jh, dirty_bh);
> >       jh->b_transaction = NULL;
> >  }
>
> I suspect the code would end up simpler if __journal_unfile_buffer() were
> to take an additional ref on the bh which it placed at *dirty_bh.
>
> Callers of __journal_unfile_buffer() could then call
>
> void handle_dirty_bh(struct buffer_head *bh)
> {
>         if (bh) {
>                 jbd_mark_buffer_dirty(bh);
>                 put_bh(bh);
>         }
> }
>
> ?
>
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