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

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Date:   Mon, 20 Aug 2018 12:38:26 +0000
From:   Javier Gonzalez <javier@...xlabs.com>
To:     Matias Bjørling <mb@...htnvm.io>
CC:     "Konopko, Igor J" <igor.j.konopko@...el.com>,
        "marcin.dziegielewski@...el.com" <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: introduce nvm_rq_to_ppa_list

> 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

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Javier

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