Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1259977

Re: [PATCH] md/raid5: fix locking in handle_stripe_clean_event()

Show all headers | View raw

Ok, thank you for clarifications!

--
Roman


31.10.2015, 01:17, "Neil Brown" <neilb@suse.de>:
> On Sat, Oct 31 2015, Shaohua Li wrote:
>
>>  On Fri, Oct 30, 2015 at 05:02:47PM +0300, Roman Gushchin wrote:
>>>  > Isn't the 4.1 fix just:
>>>  >
>>>  > diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
>>>  > index e5befa356dbe..6e4350a78257 100644
>>>  > --- a/drivers/md/raid5.c
>>>  > +++ b/drivers/md/raid5.c
>>>  > @@ -3522,16 +3522,16 @@ returnbi:
>>>  >                   * no updated data, so remove it from hash list and the stripe
>>>  >                   * will be reinitialized
>>>  >                   */
>>>  > - spin_lock_irq(&conf->device_lock);
>>>  >  unhash:
>>>  > + spin_lock_irq(conf->hash_locks + sh->hash_lock_index);
>>>  >                  remove_hash(sh);
>>>  > + spin_unlock_irq(conf->hash_locks + sh->hash_lock_index);
>>>  >                  if (head_sh->batch_head) {
>>>  >                          sh = list_first_entry(&sh->batch_list,
>>>  >                                                struct stripe_head, batch_list);
>>>  >                          if (sh != head_sh)
>>>  >                                          goto unhash;
>>>  >                  }
>>>  > - spin_unlock_irq(&conf->device_lock);
>>>  >                  sh = head_sh;
>>>  >
>>>  >                  if (test_bit(STRIPE_SYNC_REQUESTED, &sh->state))
>>>  >
>>>  > ??
>>>
>>>  In my opion, this patch looks correct, although it seems to me, that there is an another issue here.
>>>
>>>  >                  if (head_sh->batch_head) {
>>>  >                          sh = list_first_entry(&sh->batch_list,
>>>  >                                                struct stripe_head, batch_list);
>>>  >                          if (sh != head_sh)
>>>  >                                          goto unhash;
>>>  >                  }
>>>
>>>  With a patch above this code will be executed without taking any locks. It it correct?
>>>  In my opinion, we need to take at least sh->stripe_lock, which protects sh->batch_head.
>>>  Or do I miss something?
>>>
>>>  If you want, we can handle this issue separately.
>>
>>  The batch_list list doesn't need the protection. Only the remove_hash() need it.
>
> Yes, that's my understanding too. The key to understanding is that
> comment you (helpfully!) put in clear_batch_ready():
>
>         /*
>          * BATCH_READY is cleared, no new stripes can be added.
>          * batch_list can be accessed without lock
>          */
>
> I'll wrangle some patches...
>
> Thanks,
> NeilBrown
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Back to linux.kernel | Previous | Next — Previous in thread | Find similar | Unroll thread

Thread

[PATCH] md/raid5: fix locking in handle_stripe_clean_event() Roman Gushchin <klamm@yandex-team.ru> - 2015-10-28 10:00 +0100
  Re: [PATCH] md/raid5: fix locking in handle_stripe_clean_event() Neil Brown <neilb@suse.de> - 2015-10-29 01:40 +0100
    Re: [PATCH] md/raid5: fix locking in handle_stripe_clean_event() Roman Gushchin <klamm@yandex-team.ru> - 2015-10-29 15:30 +0100
      Re: [PATCH] md/raid5: fix locking in handle_stripe_clean_event() Greg KH <greg@kroah.com> - 2015-10-29 22:30 +0100
      Re: [PATCH] md/raid5: fix locking in handle_stripe_clean_event() Neil Brown <neilb@suse.de> - 2015-10-30 02:40 +0100
        Re: [PATCH] md/raid5: fix locking in handle_stripe_clean_event() Roman Gushchin <klamm@yandex-team.ru> - 2015-10-30 15:10 +0100
          Re: [PATCH] md/raid5: fix locking in handle_stripe_clean_event() Shaohua Li <shli@kernel.org> - 2015-10-30 17:30 +0100
            Re: [PATCH] md/raid5: fix locking in handle_stripe_clean_event() Neil Brown <neilb@suse.de> - 2015-10-30 23:20 +0100
              Re: [PATCH] md/raid5: fix locking in handle_stripe_clean_event() Roman Gushchin <klamm@yandex-team.ru> - 2015-10-31 13:30 +0100

csiph-web