linux-kernel - Re: [PATCH] lightnvm: introduce nvm_rq_to_ppa

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Date:   Mon, 20 Aug 2018 14:46:44 +0200
From:   Matias Bjørling <mb@...htnvm.io>
To:     javier@...xlabs.com
Cc:     igor.j.konopko@...el.com, marcin.dziegielewski@...el.com,
        hans.holmberg@...xlabs.com, hlitz@...c.edu,
        youngtack.jin@...cuitblvd.com, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] lightnvm: introduce nvm_rq_to_ppa_list

On 08/20/2018 02:38 PM, Javier Gonzalez wrote:
>> On 20 Aug 2018, at 14.12, Matias Bjørling <mb@...htnvm.io> wrote:
>>
>> There is a number of places in the lightnvm subsystem where the user
>> iterates over the ppa list. Before iterating, the user must know if it
>> is a single or multiple LBAs due to vector commands using either the
>> nvm_rq ->ppa_addr or ->ppa_list fields on command submission, which
>> leads to open-coding the if/else statement.
>>
>> Instead of having multiple if/else's, move it into a function that can
>> be called by its users.
>>
>> Signed-off-by: Matias Bjørling <mb@...htnvm.io>
>> ---
>> drivers/lightnvm/pblk-read.c  | 4 +---
>> drivers/lightnvm/pblk-write.c | 5 +----
>> drivers/lightnvm/pblk.h       | 4 +---
>> include/linux/lightnvm.h      | 5 +++++
>> 4 files changed, 8 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/lightnvm/pblk-read.c b/drivers/lightnvm/pblk-read.c
>> index f275c7e5abe4..696d3a9c9cf0 100644
>> --- a/drivers/lightnvm/pblk-read.c
>> +++ b/drivers/lightnvm/pblk-read.c
>> @@ -175,11 +175,9 @@ static void __pblk_read_put_line(struct pblk *pblk, struct ppa_addr ppa)
>>
>> static void pblk_read_put_line(struct pblk *pblk, struct nvm_rq *rqd)
>> {
>> -	struct ppa_addr *ppa_list;
>> +	struct ppa_addr *ppa_list = nvm_rq_to_ppa_list(rqd);
>> 	int i;
>>
>> -	ppa_list = (rqd->nr_ppas > 1) ? rqd->ppa_list : &rqd->ppa_addr;
>> -
>> 	for (i = 0; i < rqd->nr_ppas; i++)
>> 		__pblk_read_put_line(pblk, ppa_list[i]);
>> }
>> diff --git a/drivers/lightnvm/pblk-write.c b/drivers/lightnvm/pblk-write.c
>> index df99c45778d4..a92450ec7698 100644
>> --- a/drivers/lightnvm/pblk-write.c
>> +++ b/drivers/lightnvm/pblk-write.c
>> @@ -212,10 +212,7 @@ static void pblk_submit_rec(struct work_struct *work)
>>
>> 	pblk_log_write_err(pblk, rqd);
>>
>> -	if (rqd->nr_ppas == 1)
>> -		ppa_list = &rqd->ppa_addr;
>> -	else
>> -		ppa_list = rqd->ppa_list;
>> +	ppa_list = nvm_rq_to_ppa_list(rqd);
>>
>> 	pblk_map_remaining(pblk, ppa_list);
>> 	pblk_queue_resubmit(pblk, c_ctx);
>> diff --git a/drivers/lightnvm/pblk.h b/drivers/lightnvm/pblk.h
>> index 64ae0c7ed3bb..bda098c7cc3b 100644
>> --- a/drivers/lightnvm/pblk.h
>> +++ b/drivers/lightnvm/pblk.h
>> @@ -1335,9 +1335,7 @@ static inline int pblk_boundary_ppa_checks(struct nvm_tgt_dev *tgt_dev,
>> static inline int pblk_check_io(struct pblk *pblk, struct nvm_rq *rqd)
>> {
>> 	struct nvm_tgt_dev *dev = pblk->dev;
>> -	struct ppa_addr *ppa_list;
>> -
>> -	ppa_list = (rqd->nr_ppas > 1) ? rqd->ppa_list : &rqd->ppa_addr;
>> +	struct ppa_addr *ppa_list = nvm_rq_to_ppa_list(rqd);
>>
>> 	if (pblk_boundary_ppa_checks(dev, ppa_list, rqd->nr_ppas)) {
>> 		WARN_ON(1);
>> diff --git a/include/linux/lightnvm.h b/include/linux/lightnvm.h
>> index 0106984400bc..1497e275f90f 100644
>> --- a/include/linux/lightnvm.h
>> +++ b/include/linux/lightnvm.h
>> @@ -487,6 +487,11 @@ static inline struct ppa_addr dev_to_generic_addr(struct nvm_dev *dev,
>> 	return l;
>> }
>>
>> +static inline struct ppa_addr *nvm_rq_to_ppa_list(struct nvm_rq *rqd)
>> +{
>> +	return (rqd->nr_ppas > 1) ? rqd->ppa_list : &rqd->ppa_addr;
>> +}
>> +
>> typedef blk_qc_t (nvm_tgt_make_rq_fn)(struct request_queue *, struct bio *);
>> typedef sector_t (nvm_tgt_capacity_fn)(void *);
>> typedef void *(nvm_tgt_init_fn)(struct nvm_tgt_dev *, struct gendisk *,
>> --
>> 2.11.0
> 
> Hans made a similar patch some time ago. There are a number of places
> where you want to use this helper too, also outside of pblk. You can
> look at it here [1]
> 
> [1] https://github.com/OpenChannelSSD/linux/commits/for-4.20/pblk
> 
>     fdd88185bfed
>     17609afb2db9
> 
> Javier
> 

I like Hans' better. Hans, could you please merge my patch with yours? I 
prefer the nvm_rq_to_ppa_list naming, rqdata -> rqd, and if short-hand.