Message-ID: <0E11AFCC-AE0F-4DF4-A6DA-E57CCD423231@cnexlabs.com>
Date:   Tue, 4 Sep 2018 17:12:36 +0000
From:   Javier Gonzalez <javier@...xlabs.com>
To:     Matias Bjørling <mb@...htnvm.io>
CC:     "Konopko, Igor J" <igor.j.konopko@...el.com>,
        "Dziegielewski, Marcin" <marcin.dziegielewski@...el.com>,
        Hans Holmberg <hans.holmberg@...xlabs.com>,
        Heiner Litz <hlitz@...c.edu>,
        Young Tack Tack Jin <youngtack.jin@...cuitblvd.com>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] lightnvm: pblk: remove debug from pblk_[down/up]_page

> On 4 Sep 2018, at 02.49, Matias Bjørling <mb@...htnvm.io> wrote:
> 
> On 09/03/2018 11:12 AM, Javier Gonzalez wrote:
>>> On 31 Aug 2018, at 16.22, Matias Bjørling <mb@...htnvm.io> wrote:
>>> 
>>> On 08/31/2018 02:11 PM, Javier Gonzalez wrote:
>>>>> On 29 Aug 2018, at 16.08, Matias Bjørling <mb@...htnvm.io> wrote:
>>>>> 
>>>>> Remove the debug only iteration within __pblk_down_page, which
>>>>> then allows us to reduce the number of arguments down to pblk and
>>>>> the parallel unit from the functions that calls it. Simplifying the
>>>>> callers logic considerably.
>>>>> 
>>>>> Also, rename the functions pblk_[down/up]_page to pblk_[down/up]_pu,
>>>>> to communicate that it takes a lock on the parallel unit.
>>>>> 
>>>>> Signed-off-by: Matias Bjørling <mb@...htnvm.io>
>>>>> ---
>>>>> drivers/lightnvm/pblk-core.c     | 34 +++++++++-------------------------
>>>>> drivers/lightnvm/pblk-map.c      |  2 +-
>>>>> drivers/lightnvm/pblk-recovery.c |  6 +++---
>>>>> drivers/lightnvm/pblk-write.c    |  6 +++---
>>>>> drivers/lightnvm/pblk.h          |  6 +++---
>>>>> 5 files changed, 19 insertions(+), 35 deletions(-)
>>>>> 
>>>>> diff --git a/drivers/lightnvm/pblk-core.c b/drivers/lightnvm/pblk-core.c
>>>>> index bb1a7cc24cbb..08df6bcd2f81 100644
>>>>> --- a/drivers/lightnvm/pblk-core.c
>>>>> +++ b/drivers/lightnvm/pblk-core.c
>>>>> @@ -1861,8 +1861,7 @@ void pblk_gen_run_ws(struct pblk *pblk, struct pblk_line *line, void *priv,
>>>>> 	queue_work(wq, &line_ws->ws);
>>>>> }
>>>>> 
>>>>> -static void __pblk_down_page(struct pblk *pblk, struct ppa_addr *ppa_list,
>>>>> -			     int nr_ppas, int pos)
>>>>> +static void __pblk_down_pu(struct pblk *pblk, int pos)
>>>>> {
>>>>> 	struct pblk_lun *rlun = &pblk->luns[pos];
>>>>> 	int ret;
>>>>> @@ -1871,13 +1870,6 @@ static void __pblk_down_page(struct pblk *pblk, struct ppa_addr *ppa_list,
>>>>> 	 * Only send one inflight I/O per LUN. Since we map at a page
>>>>> 	 * granurality, all ppas in the I/O will map to the same LUN
>>>>> 	 */
>>>>> -#ifdef CONFIG_NVM_PBLK_DEBUG
>>>>> -	int i;
>>>>> -
>>>>> -	for (i = 1; i < nr_ppas; i++)
>>>>> -		WARN_ON(ppa_list[0].a.lun != ppa_list[i].a.lun ||
>>>>> -				ppa_list[0].a.ch != ppa_list[i].a.ch);
>>>>> -#endif
>>>>> 
>>>>> 	ret = down_timeout(&rlun->wr_sem, msecs_to_jiffies(30000));
>>>>> 	if (ret == -ETIME || ret == -EINTR)
>>>>> @@ -1885,21 +1877,21 @@ static void __pblk_down_page(struct pblk *pblk, struct ppa_addr *ppa_list,
>>>>> 				-ret);
>>>>> }
>>>>> 
>>>>> -void pblk_down_page(struct pblk *pblk, struct ppa_addr *ppa_list, int nr_ppas)
>>>>> +void pblk_down_pu(struct pblk *pblk, struct ppa_addr ppa)
>>>>> {
>>>>> 	struct nvm_tgt_dev *dev = pblk->dev;
>>>>> 	struct nvm_geo *geo = &dev->geo;
>>>>> -	int pos = pblk_ppa_to_pos(geo, ppa_list[0]);
>>>>> +	int pos = pblk_ppa_to_pos(geo, ppa);
>>>>> 
>>>>> -	__pblk_down_page(pblk, ppa_list, nr_ppas, pos);
>>>>> +	__pblk_down_pu(pblk, pos);
>>>>> }
>>>>> 
>>>>> -void pblk_down_rq(struct pblk *pblk, struct ppa_addr *ppa_list, int nr_ppas,
>>>>> +void pblk_down_rq(struct pblk *pblk, struct ppa_addr ppa,
>>>>> 		  unsigned long *lun_bitmap)
>>>>> {
>>>>> 	struct nvm_tgt_dev *dev = pblk->dev;
>>>>> 	struct nvm_geo *geo = &dev->geo;
>>>>> -	int pos = pblk_ppa_to_pos(geo, ppa_list[0]);
>>>>> +	int pos = pblk_ppa_to_pos(geo, ppa);
>>>>> 
>>>>> 	/* If the LUN has been locked for this same request, do no attempt to
>>>>> 	 * lock it again
>>>>> @@ -1907,23 +1899,15 @@ void pblk_down_rq(struct pblk *pblk, struct ppa_addr *ppa_list, int nr_ppas,
>>>>> 	if (test_and_set_bit(pos, lun_bitmap))
>>>>> 		return;
>>>>> 
>>>>> -	__pblk_down_page(pblk, ppa_list, nr_ppas, pos);
>>>>> +	__pblk_down_pu(pblk, pos);
>>>>> }
>>>>> 
>>>>> -void pblk_up_page(struct pblk *pblk, struct ppa_addr *ppa_list, int nr_ppas)
>>>>> +void pblk_up_pu(struct pblk *pblk, struct ppa_addr ppa)
>>>>> {
>>>>> 	struct nvm_tgt_dev *dev = pblk->dev;
>>>>> 	struct nvm_geo *geo = &dev->geo;
>>>>> 	struct pblk_lun *rlun;
>>>>> -	int pos = pblk_ppa_to_pos(geo, ppa_list[0]);
>>>>> -
>>>>> -#ifdef CONFIG_NVM_PBLK_DEBUG
>>>>> -	int i;
>>>>> -
>>>>> -	for (i = 1; i < nr_ppas; i++)
>>>>> -		WARN_ON(ppa_list[0].a.lun != ppa_list[i].a.lun ||
>>>>> -				ppa_list[0].a.ch != ppa_list[i].a.ch);
>>>>> -#endif
>>>>> +	int pos = pblk_ppa_to_pos(geo, ppa);
>>>>> 
>>>>> 	rlun = &pblk->luns[pos];
>>>>> 	up(&rlun->wr_sem);
>>>>> diff --git a/drivers/lightnvm/pblk-map.c b/drivers/lightnvm/pblk-map.c
>>>>> index dc0efb852475..ff677ca6e4e1 100644
>>>>> --- a/drivers/lightnvm/pblk-map.c
>>>>> +++ b/drivers/lightnvm/pblk-map.c
>>>>> @@ -79,7 +79,7 @@ static int pblk_map_page_data(struct pblk *pblk, unsigned int sentry,
>>>>> 		}
>>>>> 	}
>>>>> 
>>>>> -	pblk_down_rq(pblk, ppa_list, nr_secs, lun_bitmap);
>>>>> +	pblk_down_rq(pblk, ppa_list[0], lun_bitmap);
>>>>> 	return 0;
>>>>> }
>>>>> 
>>>>> diff --git a/drivers/lightnvm/pblk-recovery.c b/drivers/lightnvm/pblk-recovery.c
>>>>> index eea901d7cebc..df624d504d24 100644
>>>>> --- a/drivers/lightnvm/pblk-recovery.c
>>>>> +++ b/drivers/lightnvm/pblk-recovery.c
>>>>> @@ -227,7 +227,7 @@ static void pblk_end_io_recov(struct nvm_rq *rqd)
>>>>> 	struct pblk_pad_rq *pad_rq = rqd->private;
>>>>> 	struct pblk *pblk = pad_rq->pblk;
>>>>> 
>>>>> -	pblk_up_page(pblk, ppa_list, rqd->nr_ppas);
>>>>> +	pblk_up_pu(pblk, ppa_list[0]);
>>>>> 
>>>>> 	pblk_free_rqd(pblk, rqd, PBLK_WRITE_INT);
>>>>> 
>>>>> @@ -339,12 +339,12 @@ static int pblk_recov_pad_oob(struct pblk *pblk, struct pblk_line *line,
>>>>> 	}
>>>>> 
>>>>> 	kref_get(&pad_rq->ref);
>>>>> -	pblk_down_page(pblk, rqd->ppa_list, rqd->nr_ppas);
>>>>> +	pblk_down_pu(pblk, rqd->ppa_list[0]);
>>>>> 
>>>>> 	ret = pblk_submit_io(pblk, rqd);
>>>>> 	if (ret) {
>>>>> 		pblk_err(pblk, "I/O submission failed: %d\n", ret);
>>>>> -		pblk_up_page(pblk, rqd->ppa_list, rqd->nr_ppas);
>>>>> +		pblk_up_pu(pblk, rqd->ppa_list[0]);
>>>>> 		goto fail_free_bio;
>>>>> 	}
>>>>> 
>>>>> diff --git a/drivers/lightnvm/pblk-write.c b/drivers/lightnvm/pblk-write.c
>>>>> index cd579b440b56..55d198edd70a 100644
>>>>> --- a/drivers/lightnvm/pblk-write.c
>>>>> +++ b/drivers/lightnvm/pblk-write.c
>>>>> @@ -270,7 +270,7 @@ static void pblk_end_io_write_meta(struct nvm_rq *rqd)
>>>>> 	struct ppa_addr *ppa_list = nvm_rq_to_ppa_list(rqd);
>>>>> 	int sync;
>>>>> 
>>>>> -	pblk_up_page(pblk, ppa_list, rqd->nr_ppas);
>>>>> +	pblk_up_pu(pblk, ppa_list[0]);
>>>>> 
>>>>> 	if (rqd->error) {
>>>>> 		pblk_log_write_err(pblk, rqd);
>>>>> @@ -420,7 +420,7 @@ int pblk_submit_meta_io(struct pblk *pblk, struct pblk_line *meta_line)
>>>>> 		list_del(&meta_line->list);
>>>>> 	spin_unlock(&l_mg->close_lock);
>>>>> 
>>>>> -	pblk_down_page(pblk, ppa_list, rqd->nr_ppas);
>>>>> +	pblk_down_pu(pblk, ppa_list[0]);
>>>>> 
>>>>> 	ret = pblk_submit_io(pblk, rqd);
>>>>> 	if (ret) {
>>>>> @@ -431,7 +431,7 @@ int pblk_submit_meta_io(struct pblk *pblk, struct pblk_line *meta_line)
>>>>> 	return NVM_IO_OK;
>>>>> 
>>>>> fail_rollback:
>>>>> -	pblk_up_page(pblk, ppa_list, rqd->nr_ppas);
>>>>> +	pblk_up_pu(pblk, ppa_list[0]);
>>>>> 	spin_lock(&l_mg->close_lock);
>>>>> 	pblk_dealloc_page(pblk, meta_line, rq_ppas);
>>>>> 	list_add(&meta_line->list, &meta_line->list);
>>>>> diff --git a/drivers/lightnvm/pblk.h b/drivers/lightnvm/pblk.h
>>>>> index 2f61f4428fcb..390855375b1e 100644
>>>>> --- a/drivers/lightnvm/pblk.h
>>>>> +++ b/drivers/lightnvm/pblk.h
>>>>> @@ -823,10 +823,10 @@ u64 pblk_alloc_page(struct pblk *pblk, struct pblk_line *line, int nr_secs);
>>>>> u64 __pblk_alloc_page(struct pblk *pblk, struct pblk_line *line, int nr_secs);
>>>>> int pblk_calc_secs(struct pblk *pblk, unsigned long secs_avail,
>>>>> 		   unsigned long secs_to_flush);
>>>>> -void pblk_up_page(struct pblk *pblk, struct ppa_addr *ppa_list, int nr_ppas);
>>>>> -void pblk_down_rq(struct pblk *pblk, struct ppa_addr *ppa_list, int nr_ppas,
>>>>> +void pblk_up_pu(struct pblk *pblk, struct ppa_addr ppa);
>>>>> +void pblk_down_rq(struct pblk *pblk, struct ppa_addr ppa,
>>>>> 		  unsigned long *lun_bitmap);
>>>>> -void pblk_down_page(struct pblk *pblk, struct ppa_addr *ppa_list, int nr_ppas);
>>>>> +void pblk_down_pu(struct pblk *pblk, struct ppa_addr ppa);
>>>>> void pblk_up_rq(struct pblk *pblk, unsigned long *lun_bitmap);
>>>>> int pblk_bio_add_pages(struct pblk *pblk, struct bio *bio, gfp_t flags,
>>>>> 		       int nr_pages);
>>>>> --
>>>>> 2.11.0
>>>> The patch looks good to me. The renaming to PU though is confusing. The
>>>> underlying reason to take the semaphore is to avoid write pointer
>>>> violations. At the moment, we only have an open line in pblk, which
>>>> makes that the semaphore effectively protects a PU, but when we have
>>>> several open lines this is no longer true.
>>> 
>>> I don't understand this, how will it change when multiple lines are active?
>>> 
>>> My guess is that one has to keep track of the number of outstanding
>>> I/Os for each PU.
>> The confusion comes from the current semaphore having 2 purposes: (i)
>> guaranteeing the write pointer at a chunk level, and (ii) being the
>> mechanism used by the scheduler to minimize internal write collisions.
>> When we have several open lines this semaphore will still be used for
>> (i), however, we will need a separate mechanism for (ii).
>>> Regarding naming, pblk_[down/up]_line doesn't quite cut it, and _page
>>> doesn't mean anything to me. Can we find a better name?
>> Give the above, what do you say pblk_[down/up]_chunk?
> 
> Ok, works for me. I'll update the patch and push. If getting to
> multiple chunks per PU, then this can be flushed out to remove the
> rest of the confusion.
> 
> Thanks.

Great. Thanks!


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