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?
Thanks,
NeilBrown
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