On Mon, 2008-08-04 at 14:50 -0700, Andrew Morton wrote:
> On Mon, 04 Aug 2008 20:10:33 +0900
> Hisashi Hifumi <hifumi.hisashi@xxxxxxxxxxxxx> wrote:
>
> > Hi
> >
> > Dio write returns EIO when try_to_release_page fails because bh is
> > still referenced.
> >
> > diff -Nrup linux-2.6.27-rc1.org/fs/jbd/transaction.c linux-2.6.27-rc1/fs/jbd/transaction.c
> > --- linux-2.6.27-rc1.org/fs/jbd/transaction.c 2008-07-29 19:28:47.000000000 +0900
> > +++ linux-2.6.27-rc1/fs/jbd/transaction.c 2008-07-29 20:40:12.000000000 +0900
> > @@ -1764,6 +1764,12 @@ int journal_try_to_free_buffers(journal_
> > */
> > if (ret == 0 && (gfp_mask & __GFP_WAIT) && (gfp_mask & __GFP_FS)) {
> > journal_wait_for_transaction_sync_data(journal);
> > +
> > + bh = head;
> > + do {
> > + while (atomic_read(&bh->b_count))
> > + schedule();
> > + } while ((bh = bh->b_this_page) != head);
> > ret = try_to_free_buffers(page);
> > }
>
> The loop is problematic. If the scheduler decides to keep running this
> task then we have a busy loop. If this task has realtime policy then
> it might even lock up the kernel.
>
ocfs2 calls journal_try_to_free_buffers too, looping on b_count might
not be the best idea there either.
This code gets called from releasepage, which is used other places than
the O_DIRECT invalidation paths, I'd be worried about performance
problems here.
-chris
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