Re: [PATCH-v2 2/9] target/pr: Use atomic bitop for se_dev_entry->pr_reg reservation check

Christoph Hellwig
2015-05-22T11:52:08Z

>
> -/*
> - * this function can be called with struct se_device->dev_reservation_lock
> - * when register_move = 1
> - */
> static void __core_scsi3_add_registration(
> struct se_device *dev,
> struct se_node_acl *nacl,
> @@ -1023,6 +1021,7 @@ static void __core_scsi3_add_registration(
> const struct target_core_fabric_ops *tfo = nacl->se_tpg->se_tpg_tfo;
> struct t10_pr_registration *pr_reg_tmp, *pr_reg_tmp_safe;
> struct t10_reservation *pr_tmpl = &dev->t10_pr;
> + struct se_dev_entry *deve;
>
> /*
> * Increment PRgeneration counter for struct se_device upon a successful
> @@ -1039,10 +1038,16 @@ static void __core_scsi3_add_registration(
>
> spin_lock(&pr_tmpl->registration_lock);
> list_add_tail(&pr_reg->pr_reg_list, &pr_tmpl->registration_list);
> - pr_reg->pr_reg_deve->def_pr_registered = 1;
>
> __core_scsi3_dump_registration(tfo, dev, nacl, pr_reg, register_type);
> spin_unlock(&pr_tmpl->registration_lock);
> +
> + mutex_lock(&nacl->lun_entry_mutex);
> + deve = target_nacl_find_deve(nacl, pr_reg->pr_res_mapped_lun);
> + if (deve)
> + set_bit(1, &deve->pr_reg);
> + mutex_unlock(&nacl->lun_entry_mutex);

Why can't we rely on pr_reg->pr_reg_deve here? The way the it's
set up is a bit convoluted, but unless I miss something it needs to
have a reference if it's set (and it it doesn't that needs to be fixed
ASAP).

Also even if we would need a target_nacl_find_deve call here it could
be done under rcu_read_lock as lun_entry_hlist isn't modified.

> + mutex_lock(&nacl->lun_entry_mutex);
> + deve = target_nacl_find_deve(nacl_tmp, pr_reg_tmp->pr_res_mapped_lun);
> + if (deve)
> + set_bit(1, &deve->pr_reg);
> + mutex_unlock(&nacl->lun_entry_mutex);
> +

Same here.

> @@ -1258,6 +1269,8 @@ static void __core_scsi3_free_registration(
> */
> if (dec_holders)
> core_scsi3_put_pr_reg(pr_reg);
> +
> + spin_unlock(&pr_tmpl->registration_lock);
> /*
> * Wait until all reference from any other I_T nexuses for this
> * *pr_reg have been released. Because list_del() is called above,
> @@ -1265,13 +1278,18 @@ static void __core_scsi3_free_registration(
> * count back to zero, and we release *pr_reg.
> */
> while (atomic_read(&pr_reg->pr_res_holders) != 0) {
> - spin_unlock(&pr_tmpl->registration_lock);
> pr_debug("SPC-3 PR [%s] waiting for pr_res_holders\n",
> tfo->get_fabric_name());
> cpu_relax();
> - spin_lock(&pr_tmpl->registration_lock);
> }
>
> + mutex_lock(&nacl->lun_entry_mutex);
> + deve = target_nacl_find_deve(nacl, pr_reg->pr_res_mapped_lun);
> + if (deve)
> + clear_bit(1, &deve->pr_reg);
> + mutex_unlock(&nacl->lun_entry_mutex);

And here.