On Mon, Jul 02, 2012 at 10:46:48AM +1000, NeilBrown wrote:
> On Mon, 25 Jun 2012 15:24:49 +0800 Shaohua Li <shli@xxxxxxxxxx> wrote:
>
> > There isn't locking setting STRIPE_DELAYED and STRIPE_PREREAD_ACTIVE bits, but
> > the two bits have relationship. A delayed stripe can be moved to hold list only
> > when preread active stripe count is below IO_THRESHOLD. If a stripe has both
> > the bits set, such stripe will be in delayed list and preread count not 0,
> > which will make such stripe never leave delayed list.
> >
> > Signed-off-by: Shaohua Li <shli@xxxxxxxxxxxx>
> > ---
> > drivers/md/raid5.c | 4 +++-
> > 1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > Index: linux/drivers/md/raid5.c
> > ===================================================================
> > --- linux.orig/drivers/md/raid5.c 2012-06-25 14:36:15.964613183 +0800
> > +++ linux/drivers/md/raid5.c 2012-06-25 14:36:57.280096788 +0800
> > @@ -196,12 +196,14 @@ static void __release_stripe(struct r5co
> > BUG_ON(!list_empty(&sh->lru));
> > BUG_ON(atomic_read(&conf->active_stripes)==0);
> > if (test_bit(STRIPE_HANDLE, &sh->state)) {
> > - if (test_bit(STRIPE_DELAYED, &sh->state))
> > + if (test_bit(STRIPE_DELAYED, &sh->state) &&
> > + !test_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
> > list_add_tail(&sh->lru, &conf->delayed_list);
> > else if (test_bit(STRIPE_BIT_DELAY, &sh->state) &&
> > sh->bm_seq - conf->seq_write > 0)
> > list_add_tail(&sh->lru, &conf->bitmap_list);
> > else {
> > + clear_bit(STRIPE_DELAYED, &sh->state);
> > clear_bit(STRIPE_BIT_DELAY, &sh->state);
> > list_add_tail(&sh->lru, &conf->handle_list);
> > }
>
> Thanks. I've applied this patch and will submit it upstream shortly.
>
> Have you actually seen a stripe get trapped with both bits set, or is this
> just a theoretical problem discovered by code inspection?
I print the flags of strip when there is overlap sleep in make_request(), and
found this case, so this is real.
How do you think about the other patches in the series?
Thanks,
Shaohua
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