> On 22 Mar 2019, at 13.01, Marcin Dziegielewski <marcin.dziegielewski@xxxxxxxxx> wrote:
>
>
>
> On 3/21/19 10:32 AM, Javier González wrote:
>>> On 20 Mar 2019, at 16.38, Marcin Dziegielewski <marcin.dziegielewski@xxxxxxxxx> wrote:
>>>
>>> Currently if we issue reboot to the system pblk will close
>>> ungracefully and in consequence it will need recovery on load.
>>>
>>> This patch propose utilize of reboot notifier feature to trigger
>>> gracefull pblk shutdown on reboot.
>>>
>>> Signed-off-by: Marcin Dziegielewski <marcin.dziegielewski@xxxxxxxxx>
>>> ---
>>> drivers/lightnvm/core.c | 64 +++++++++++++++++++++++++++++++++++++++----------
>>> 1 file changed, 51 insertions(+), 13 deletions(-)
>>>
>>> diff --git a/drivers/lightnvm/core.c b/drivers/lightnvm/core.c
>>> index 5f82036..5488051 100644
>>> --- a/drivers/lightnvm/core.c
>>> +++ b/drivers/lightnvm/core.c
>>> @@ -27,6 +27,7 @@
>>> #include <linux/miscdevice.h>
>>> #include <linux/lightnvm.h>
>>> #include <linux/sched/sysctl.h>
>>> +#include <linux/reboot.h>
>>>
>>> static LIST_HEAD(nvm_tgt_types);
>>> static DECLARE_RWSEM(nvm_tgtt_lock);
>>> @@ -1138,6 +1139,48 @@ struct nvm_dev *nvm_alloc_dev(int node)
>>> }
>>> EXPORT_SYMBOL(nvm_alloc_dev);
>>>
>>> +static void _nvm_unregister(struct nvm_dev *dev, bool graceful)
>>> +{
>>> + struct nvm_target *t, *tmp;
>>> +
>>> + mutex_lock(&dev->mlock);
>>> + list_for_each_entry_safe(t, tmp, &dev->targets, list) {
>>> + if (t->dev->parent != dev)
>>> + continue;
>>> + __nvm_remove_target(t, graceful);
>>> + }
>>> + mutex_unlock(&dev->mlock);
>>> +
>>> + list_del(&dev->devices);
>>> +
>>> + nvm_free(dev);
>>> +}
>>> +
>>> +static int nvm_notify_reboot(struct notifier_block *this,
>>> + unsigned long code, void *x)
>>> +{
>>> + struct nvm_dev *dev, *t;
>>> +
>>> + down_write(&nvm_lock);
>>> + if (list_empty(&nvm_devices)) {
>>> + up_write(&nvm_lock);
>>> + return NOTIFY_DONE;
>>> + }
>>> +
>>> + list_for_each_entry_safe(dev, t, &nvm_devices, devices)
>>> + _nvm_unregister(dev, true);
>>> +
>>> + up_write(&nvm_lock);
>>> +
>>> + return NOTIFY_DONE;
>>> +}
>>> +
>>> +static struct notifier_block nvm_notifier = {
>>> + .notifier_call = nvm_notify_reboot,
>>> + .next = NULL,
>>> + .priority = INT_MAX, /* before any real devices */
>> Why this priority?
>
> I believe that is the safest priority for our case, I based on bcache
> approach. Should I use other priority?
>
I’m not very familiar with the notifier_block. I quick look showed that
most modules do not use it, that’s what I asked. Not real feedback here.
>>> +};
>>> +
>>> int nvm_register(struct nvm_dev *dev)
>>> {
>>> int ret, exp_pool_size;
>>> @@ -1161,8 +1204,11 @@ int nvm_register(struct nvm_dev *dev)
>>> return -ENOMEM;
>>> }
>>>
>>> - /* register device with a supported media manager */
>>> down_write(&nvm_lock);
>>> + if (list_empty(&nvm_devices))
>>> + register_reboot_notifier(&nvm_notifier);
>>> +
>>> + /* register device with a supported media manager */
>>> list_add(&dev->devices, &nvm_devices);
>>> up_write(&nvm_lock);
>>>
>>> @@ -1172,21 +1218,13 @@ int nvm_register(struct nvm_dev *dev)
>>>
>>> void nvm_unregister(struct nvm_dev *dev)
>>> {
>>> - struct nvm_target *t, *tmp;
>>> + down_write(&nvm_lock);
>>>
>>> - mutex_lock(&dev->mlock);
>>> - list_for_each_entry_safe(t, tmp, &dev->targets, list) {
>>> - if (t->dev->parent != dev)
>>> - continue;
>>> - __nvm_remove_target(t, false);
>>> - }
>>> - mutex_unlock(&dev->mlock);
>>> + _nvm_unregister(dev, false);
>> You are adding an extra lock dependency here. I cannot see any obvious
>> problem with it, but you probably want to test this with lock debugging
>> enabled.
>
> It was good suggestion, thanks. With enabled lock debugging I have found
> one potential deadlock, I will send second version of this patch.
>
Cool.
>>> - down_write(&nvm_lock);
>>> - list_del(&dev->devices);
>>> + if (list_empty(&nvm_devices))
>>> + unregister_reboot_notifier(&nvm_notifier);
>>> up_write(&nvm_lock);
>>> -
>>> - nvm_free(dev);
>>> }
>>> EXPORT_SYMBOL(nvm_unregister);
>>>
>>> --
>>> 1.8.3.1
>> Otherwise, I think adding this functionality is beneficial.
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