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Subject: Re: [PATCH 3/3] lightnvm: pblk: support variable OOB size
To:     javier@javigon.com
Cc:     igor.j.konopko@intel.com, marcin.dziegielewski@intel.com,
        linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
        javier@cnexlabs.com
References: <1535537370-10729-1-git-send-email-javier@cnexlabs.com>
 <1535537370-10729-4-git-send-email-javier@cnexlabs.com>
From:   =?UTF-8?Q?Matias_Bj=c3=b8rling?= <mb@lightnvm.io>
Message-ID: <5298a07e-eecd-4eca-ce0b-a87977d0c298@lightnvm.io>
Date:   Mon, 10 Sep 2018 12:21:29 +0200
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On 08/29/2018 12:09 PM, Javier González wrote:
> pblk uses 8 bytes in the metadata region area exposed by the device
> through the out of band area to store the lba mapped to the given
> physical sector. This is used for recovery purposes. Given that the
> first generation OCSSD devices exposed 16 bytes, pblk used a hard-coded
> structure for this purpose.
> 
> This patch relaxes the 16 bytes assumption and uses the metadata size
> reported by the device to layout metadata appropriately for the vector
> commands. This adds support for arbitrary metadata sizes, as long as
> these are larger than 8 bytes. Note that this patch does not address the
> case in which the device does not expose an out of band area and that
> pblk creation will fail in this case.
> 
> Signed-off-by: Javier González <javier@cnexlabs.com>
> ---
>   drivers/lightnvm/pblk-core.c     | 56 ++++++++++++++++++++++++++++++----------
>   drivers/lightnvm/pblk-init.c     | 14 ++++++++++
>   drivers/lightnvm/pblk-map.c      | 19 +++++++++-----
>   drivers/lightnvm/pblk-read.c     | 55 +++++++++++++++++++++++++--------------
>   drivers/lightnvm/pblk-recovery.c | 34 +++++++++++++++++-------
>   drivers/lightnvm/pblk.h          | 18 ++++++++++---
>   6 files changed, 143 insertions(+), 53 deletions(-)
> 
> diff --git a/drivers/lightnvm/pblk-core.c b/drivers/lightnvm/pblk-core.c
> index a311cc29afd8..d52e0047ae9d 100644
> --- a/drivers/lightnvm/pblk-core.c
> +++ b/drivers/lightnvm/pblk-core.c
> @@ -250,8 +250,20 @@ int pblk_setup_rqd(struct pblk *pblk, struct nvm_rq *rqd, gfp_t mem_flags,
>   	if (!is_vector)
>   		return 0;
>   
> -	rqd->ppa_list = rqd->meta_list + pblk_dma_meta_size;
> -	rqd->dma_ppa_list = rqd->dma_meta_list + pblk_dma_meta_size;
> +	if (pblk->dma_shared) {
> +		rqd->ppa_list = rqd->meta_list + pblk->dma_meta_size;
> +		rqd->dma_ppa_list = rqd->dma_meta_list + pblk->dma_meta_size;
> +
> +		return 0;
> +	}
> +
> +	rqd->ppa_list = nvm_dev_dma_alloc(dev->parent, mem_flags,
> +							&rqd->dma_ppa_list);
> +	if (!rqd->ppa_list) {
> +		nvm_dev_dma_free(dev->parent, rqd->meta_list,
> +							rqd->dma_meta_list);
> +		return -ENOMEM;
> +	}
>   
>   	return 0;
>   }
> @@ -262,7 +274,11 @@ void pblk_clear_rqd(struct pblk *pblk, struct nvm_rq *rqd)
>   
>   	if (rqd->meta_list)
>   		nvm_dev_dma_free(dev->parent, rqd->meta_list,
> -				rqd->dma_meta_list);
> +							rqd->dma_meta_list);
> +
> +	if (!pblk->dma_shared && rqd->ppa_list)
> +		nvm_dev_dma_free(dev->parent, rqd->ppa_list,
> +							rqd->dma_ppa_list);
>   }
>   
>   /* Caller must guarantee that the request is a valid type */
> @@ -796,10 +812,12 @@ static int pblk_line_smeta_write(struct pblk *pblk, struct pblk_line *line,
>   	rqd.is_seq = 1;
>   
>   	for (i = 0; i < lm->smeta_sec; i++, paddr++) {
> -		struct pblk_sec_meta *meta_list = rqd.meta_list;
> +		struct pblk_sec_meta *meta;
>   
>   		rqd.ppa_list[i] = addr_to_gen_ppa(pblk, paddr, line->id);
> -		meta_list[i].lba = lba_list[paddr] = addr_empty;
> +
> +		meta = sec_meta_index(pblk, rqd.meta_list, i);
> +		meta->lba = lba_list[paddr] = addr_empty;
>   	}
>   
>   	ret = pblk_submit_io_sync_sem(pblk, &rqd);
> @@ -845,8 +863,17 @@ int pblk_line_emeta_read(struct pblk *pblk, struct pblk_line *line,
>   	if (!meta_list)
>   		return -ENOMEM;
>   
> -	ppa_list = meta_list + pblk_dma_meta_size;
> -	dma_ppa_list = dma_meta_list + pblk_dma_meta_size;
> +	if (pblk->dma_shared) {
> +		ppa_list = meta_list + pblk->dma_meta_size;
> +		dma_ppa_list = dma_meta_list + pblk->dma_meta_size;
> +	} else {
> +		ppa_list = nvm_dev_dma_alloc(dev->parent, GFP_KERNEL,
> +							&dma_ppa_list);
> +		if (!ppa_list) {
> +			ret = -ENOMEM;
> +			goto free_meta_list;
> +		}
> +	}
>   
>   next_rq:
>   	memset(&rqd, 0, sizeof(struct nvm_rq));
> @@ -858,7 +885,7 @@ int pblk_line_emeta_read(struct pblk *pblk, struct pblk_line *line,
>   					l_mg->emeta_alloc_type, GFP_KERNEL);
>   	if (IS_ERR(bio)) {
>   		ret = PTR_ERR(bio);
> -		goto free_rqd_dma;
> +		goto free_ppa_list;
>   	}
>   
>   	bio->bi_iter.bi_sector = 0; /* internal bio */
> @@ -884,7 +911,7 @@ int pblk_line_emeta_read(struct pblk *pblk, struct pblk_line *line,
>   			if (pblk_boundary_paddr_checks(pblk, paddr)) {
>   				bio_put(bio);
>   				ret = -EINTR;
> -				goto free_rqd_dma;
> +				goto free_ppa_list;
>   			}
>   
>   			ppa = addr_to_gen_ppa(pblk, paddr, line_id);
> @@ -894,7 +921,7 @@ int pblk_line_emeta_read(struct pblk *pblk, struct pblk_line *line,
>   		if (pblk_boundary_paddr_checks(pblk, paddr + min)) {
>   			bio_put(bio);
>   			ret = -EINTR;
> -			goto free_rqd_dma;
> +			goto free_ppa_list;
>   		}
>   
>   		for (j = 0; j < min; j++, i++, paddr++)
> @@ -905,7 +932,7 @@ int pblk_line_emeta_read(struct pblk *pblk, struct pblk_line *line,
>   	if (ret) {
>   		pblk_err(pblk, "emeta I/O submission failed: %d\n", ret);
>   		bio_put(bio);
> -		goto free_rqd_dma;
> +		goto free_ppa_list;
>   	}
>   
>   	atomic_dec(&pblk->inflight_io);
> @@ -918,8 +945,11 @@ int pblk_line_emeta_read(struct pblk *pblk, struct pblk_line *line,
>   	if (left_ppas)
>   		goto next_rq;
>   
> -free_rqd_dma:
> -	nvm_dev_dma_free(dev->parent, rqd.meta_list, rqd.dma_meta_list);
> +free_ppa_list:
> +	if (!pblk->dma_shared)
> +		nvm_dev_dma_free(dev->parent, ppa_list, dma_ppa_list);
> +free_meta_list:
> +	nvm_dev_dma_free(dev->parent, meta_list, dma_meta_list);
>   	return ret;
>   }
>   
> diff --git a/drivers/lightnvm/pblk-init.c b/drivers/lightnvm/pblk-init.c
> index a99854439224..57972156c318 100644
> --- a/drivers/lightnvm/pblk-init.c
> +++ b/drivers/lightnvm/pblk-init.c
> @@ -354,6 +354,20 @@ static int pblk_core_init(struct pblk *pblk)
>   	struct nvm_geo *geo = &dev->geo;
>   	int ret, max_write_ppas;
>   
> +	if (sizeof(struct pblk_sec_meta) > geo->sos) {
> +		pblk_err(pblk, "OOB area too small. Min %lu bytes (%d)\n",
> +			(unsigned long)sizeof(struct pblk_sec_meta), geo->sos);
> +		return -EINTR;
> +	}
> +
> +	pblk->dma_ppa_size = (sizeof(u64) * NVM_MAX_VLBA);
> +	pblk->dma_meta_size = geo->sos * NVM_MAX_VLBA;
> +
> +	if (pblk->dma_ppa_size + pblk->dma_meta_size > PAGE_SIZE)
> +		pblk->dma_shared = false;
> +	else
> +		pblk->dma_shared = true;
> +
>   	atomic64_set(&pblk->user_wa, 0);
>   	atomic64_set(&pblk->pad_wa, 0);
>   	atomic64_set(&pblk->gc_wa, 0);
> diff --git a/drivers/lightnvm/pblk-map.c b/drivers/lightnvm/pblk-map.c
> index dc0efb852475..55fca16d18e4 100644
> --- a/drivers/lightnvm/pblk-map.c
> +++ b/drivers/lightnvm/pblk-map.c
> @@ -25,6 +25,7 @@ static int pblk_map_page_data(struct pblk *pblk, unsigned int sentry,
>   			      unsigned int valid_secs)
>   {
>   	struct pblk_line *line = pblk_line_get_data(pblk);
> +	struct pblk_sec_meta *meta;
>   	struct pblk_emeta *emeta;
>   	struct pblk_w_ctx *w_ctx;
>   	__le64 *lba_list;
> @@ -56,6 +57,8 @@ static int pblk_map_page_data(struct pblk *pblk, unsigned int sentry,
>   		/* ppa to be sent to the device */
>   		ppa_list[i] = addr_to_gen_ppa(pblk, paddr, line->id);
>   
> +		meta = sec_meta_index(pblk, meta_list, i);
> +
>   		/* Write context for target bio completion on write buffer. Note
>   		 * that the write buffer is protected by the sync backpointer,
>   		 * and a single writer thread have access to each specific entry
> @@ -67,14 +70,14 @@ static int pblk_map_page_data(struct pblk *pblk, unsigned int sentry,
>   			kref_get(&line->ref);
>   			w_ctx = pblk_rb_w_ctx(&pblk->rwb, sentry + i);
>   			w_ctx->ppa = ppa_list[i];
> -			meta_list[i].lba = cpu_to_le64(w_ctx->lba);
> +			meta->lba = cpu_to_le64(w_ctx->lba);
>   			lba_list[paddr] = cpu_to_le64(w_ctx->lba);
>   			if (lba_list[paddr] != addr_empty)
>   				line->nr_valid_lbas++;
>   			else
>   				atomic64_inc(&pblk->pad_wa);
>   		} else {
> -			lba_list[paddr] = meta_list[i].lba = addr_empty;
> +			lba_list[paddr] = meta->lba = addr_empty;
>   			__pblk_map_invalidate(pblk, line, paddr);
>   		}
>   	}
> @@ -87,7 +90,7 @@ void pblk_map_rq(struct pblk *pblk, struct nvm_rq *rqd, unsigned int sentry,
>   		 unsigned long *lun_bitmap, unsigned int valid_secs,
>   		 unsigned int off)
>   {
> -	struct pblk_sec_meta *meta_list = rqd->meta_list;
> +	struct pblk_sec_meta *meta_list;
>   	struct ppa_addr *ppa_list = nvm_rq_to_ppa_list(rqd);
>   	unsigned int map_secs;
>   	int min = pblk->min_write_pgs;
> @@ -95,8 +98,10 @@ void pblk_map_rq(struct pblk *pblk, struct nvm_rq *rqd, unsigned int sentry,
>   
>   	for (i = off; i < rqd->nr_ppas; i += min) {
>   		map_secs = (i + min > valid_secs) ? (valid_secs % min) : min;
> +		meta_list = sec_meta_index(pblk, rqd->meta_list, i);
> +
>   		if (pblk_map_page_data(pblk, sentry + i, &ppa_list[i],
> -					lun_bitmap, &meta_list[i], map_secs)) {
> +					lun_bitmap, meta_list, map_secs)) {
>   			bio_put(rqd->bio);
>   			pblk_free_rqd(pblk, rqd, PBLK_WRITE);
>   			pblk_pipeline_stop(pblk);
> @@ -112,8 +117,8 @@ void pblk_map_erase_rq(struct pblk *pblk, struct nvm_rq *rqd,
>   	struct nvm_tgt_dev *dev = pblk->dev;
>   	struct nvm_geo *geo = &dev->geo;
>   	struct pblk_line_meta *lm = &pblk->lm;
> -	struct pblk_sec_meta *meta_list = rqd->meta_list;
>   	struct ppa_addr *ppa_list = nvm_rq_to_ppa_list(rqd);
> +	struct pblk_sec_meta *meta_list;
>   	struct pblk_line *e_line, *d_line;
>   	unsigned int map_secs;
>   	int min = pblk->min_write_pgs;
> @@ -121,8 +126,10 @@ void pblk_map_erase_rq(struct pblk *pblk, struct nvm_rq *rqd,
>   
>   	for (i = 0; i < rqd->nr_ppas; i += min) {
>   		map_secs = (i + min > valid_secs) ? (valid_secs % min) : min;
> +		meta_list = sec_meta_index(pblk, rqd->meta_list, i);
> +
>   		if (pblk_map_page_data(pblk, sentry + i, &ppa_list[i],
> -					lun_bitmap, &meta_list[i], map_secs)) {
> +					lun_bitmap, meta_list, map_secs)) {
>   			bio_put(rqd->bio);
>   			pblk_free_rqd(pblk, rqd, PBLK_WRITE);
>   			pblk_pipeline_stop(pblk);
> diff --git a/drivers/lightnvm/pblk-read.c b/drivers/lightnvm/pblk-read.c
> index 57d3155ef9a5..12b690e2abd9 100644
> --- a/drivers/lightnvm/pblk-read.c
> +++ b/drivers/lightnvm/pblk-read.c
> @@ -42,7 +42,6 @@ static void pblk_read_ppalist_rq(struct pblk *pblk, struct nvm_rq *rqd,
>   				 struct bio *bio, sector_t blba,
>   				 unsigned long *read_bitmap)
>   {
> -	struct pblk_sec_meta *meta_list = rqd->meta_list;
>   	struct ppa_addr ppas[NVM_MAX_VLBA];
>   	int nr_secs = rqd->nr_ppas;
>   	bool advanced_bio = false;
> @@ -51,13 +50,16 @@ static void pblk_read_ppalist_rq(struct pblk *pblk, struct nvm_rq *rqd,
>   	pblk_lookup_l2p_seq(pblk, ppas, blba, nr_secs);
>   
>   	for (i = 0; i < nr_secs; i++) {
> +		struct pblk_sec_meta *meta;
>   		struct ppa_addr p = ppas[i];
>   		sector_t lba = blba + i;
>   
> +		meta = sec_meta_index(pblk, rqd->meta_list, i);
>   retry:
>   		if (pblk_ppa_empty(p)) {
>   			WARN_ON(test_and_set_bit(i, read_bitmap));
> -			meta_list[i].lba = cpu_to_le64(ADDR_EMPTY);
> +
> +			meta->lba = cpu_to_le64(ADDR_EMPTY);
>   
>   			if (unlikely(!advanced_bio)) {
>   				bio_advance(bio, (i) * PBLK_EXPOSED_PAGE_SIZE);
> @@ -77,7 +79,7 @@ static void pblk_read_ppalist_rq(struct pblk *pblk, struct nvm_rq *rqd,
>   				goto retry;
>   			}
>   			WARN_ON(test_and_set_bit(i, read_bitmap));
> -			meta_list[i].lba = cpu_to_le64(lba);
> +			meta->lba = cpu_to_le64(lba);
>   			advanced_bio = true;
>   #ifdef CONFIG_NVM_PBLK_DEBUG
>   			atomic_long_inc(&pblk->cache_reads);
> @@ -104,12 +106,15 @@ static void pblk_read_ppalist_rq(struct pblk *pblk, struct nvm_rq *rqd,
>   static void pblk_read_check_seq(struct pblk *pblk, struct nvm_rq *rqd,
>   				sector_t blba)
>   {
> -	struct pblk_sec_meta *meta_lba_list = rqd->meta_list;
>   	int nr_lbas = rqd->nr_ppas;
>   	int i;
>   
>   	for (i = 0; i < nr_lbas; i++) {
> -		u64 lba = le64_to_cpu(meta_lba_list[i].lba);
> +		struct pblk_sec_meta *meta;
> +		u64 lba;
> +
> +		meta = sec_meta_index(pblk, rqd->meta_list, i);
> +		lba = le64_to_cpu(meta->lba);
>   
>   		if (lba == ADDR_EMPTY)
>   			continue;
> @@ -133,17 +138,18 @@ static void pblk_read_check_seq(struct pblk *pblk, struct nvm_rq *rqd,
>   static void pblk_read_check_rand(struct pblk *pblk, struct nvm_rq *rqd,
>   				 u64 *lba_list, int nr_lbas)
>   {
> -	struct pblk_sec_meta *meta_lba_list = rqd->meta_list;
>   	int i, j;
>   
>   	for (i = 0, j = 0; i < nr_lbas; i++) {
> +		struct pblk_sec_meta *meta;
>   		u64 lba = lba_list[i];
>   		u64 meta_lba;
>   
>   		if (lba == ADDR_EMPTY)
>   			continue;
>   
> -		meta_lba = le64_to_cpu(meta_lba_list[j].lba);
> +		meta = sec_meta_index(pblk, rqd->meta_list, j);
> +		meta_lba = le64_to_cpu(meta->lba);
>   
>   		if (lba != meta_lba) {
>   #ifdef CONFIG_NVM_PBLK_DEBUG
> @@ -218,7 +224,7 @@ static void pblk_end_partial_read(struct nvm_rq *rqd)
>   	struct bio *new_bio = rqd->bio;
>   	struct bio *bio = pr_ctx->orig_bio;
>   	struct bio_vec src_bv, dst_bv;
> -	struct pblk_sec_meta *meta_list = rqd->meta_list;
> +	struct pblk_sec_meta *meta;
>   	int bio_init_idx = pr_ctx->bio_init_idx;
>   	unsigned long *read_bitmap = pr_ctx->bitmap;
>   	int nr_secs = pr_ctx->orig_nr_secs;
> @@ -237,12 +243,13 @@ static void pblk_end_partial_read(struct nvm_rq *rqd)
>   	}
>   
>   	/* Re-use allocated memory for intermediate lbas */
> -	lba_list_mem = (((void *)rqd->ppa_list) + pblk_dma_ppa_size);
> -	lba_list_media = (((void *)rqd->ppa_list) + 2 * pblk_dma_ppa_size);
> +	lba_list_mem = (((void *)rqd->ppa_list) + pblk->dma_ppa_size);
> +	lba_list_media = (((void *)rqd->ppa_list) + 2 * pblk->dma_ppa_size);
>   
>   	for (i = 0; i < nr_secs; i++) {
> -		lba_list_media[i] = meta_list[i].lba;
> -		meta_list[i].lba = lba_list_mem[i];
> +		meta = sec_meta_index(pblk, rqd->meta_list, i);
> +		lba_list_media[i] = meta->lba;
> +		meta->lba = lba_list_mem[i];
>   	}
>   
>   	/* Fill the holes in the original bio */
> @@ -254,7 +261,8 @@ static void pblk_end_partial_read(struct nvm_rq *rqd)
>   		line = pblk_ppa_to_line(pblk, rqd->ppa_list[i]);
>   		kref_put(&line->ref, pblk_line_put);
>   
> -		meta_list[hole].lba = lba_list_media[i];
> +		meta = sec_meta_index(pblk, rqd->meta_list, hole);
> +		meta->lba = lba_list_media[i];
>   
>   		src_bv = new_bio->bi_io_vec[i++];
>   		dst_bv = bio->bi_io_vec[bio_init_idx + hole];
> @@ -290,8 +298,8 @@ static int pblk_setup_partial_read(struct pblk *pblk, struct nvm_rq *rqd,
>   			    unsigned long *read_bitmap,
>   			    int nr_holes)
>   {
> -	struct pblk_sec_meta *meta_list = rqd->meta_list;
>   	struct pblk_g_ctx *r_ctx = nvm_rq_to_pdu(rqd);
> +	struct pblk_sec_meta *meta;
>   	struct pblk_pr_ctx *pr_ctx;
>   	struct bio *new_bio, *bio = r_ctx->private;
>   	__le64 *lba_list_mem;
> @@ -299,7 +307,7 @@ static int pblk_setup_partial_read(struct pblk *pblk, struct nvm_rq *rqd,
>   	int i;
>   
>   	/* Re-use allocated memory for intermediate lbas */
> -	lba_list_mem = (((void *)rqd->ppa_list) + pblk_dma_ppa_size);
> +	lba_list_mem = (((void *)rqd->ppa_list) + pblk->dma_ppa_size);
>   
>   	new_bio = bio_alloc(GFP_KERNEL, nr_holes);
>   
> @@ -315,8 +323,10 @@ static int pblk_setup_partial_read(struct pblk *pblk, struct nvm_rq *rqd,
>   	if (!pr_ctx)
>   		goto fail_free_pages;
>   
> -	for (i = 0; i < nr_secs; i++)
> -		lba_list_mem[i] = meta_list[i].lba;
> +	for (i = 0; i < nr_secs; i++) {
> +		meta = sec_meta_index(pblk, rqd->meta_list, i);
> +		lba_list_mem[i] = meta->lba;
> +	}
>   
>   	new_bio->bi_iter.bi_sector = 0; /* internal bio */
>   	bio_set_op_attrs(new_bio, REQ_OP_READ, 0);
> @@ -382,7 +392,7 @@ static int pblk_partial_read_bio(struct pblk *pblk, struct nvm_rq *rqd,
>   static void pblk_read_rq(struct pblk *pblk, struct nvm_rq *rqd, struct bio *bio,
>   			 sector_t lba, unsigned long *read_bitmap)
>   {
> -	struct pblk_sec_meta *meta_list = rqd->meta_list;
> +	struct pblk_sec_meta *meta;
>   	struct ppa_addr ppa;
>   
>   	pblk_lookup_l2p_seq(pblk, &ppa, lba, 1);
> @@ -394,7 +404,10 @@ static void pblk_read_rq(struct pblk *pblk, struct nvm_rq *rqd, struct bio *bio,
>   retry:
>   	if (pblk_ppa_empty(ppa)) {
>   		WARN_ON(test_and_set_bit(0, read_bitmap));
> -		meta_list[0].lba = cpu_to_le64(ADDR_EMPTY);
> +
> +		meta = sec_meta_index(pblk, rqd->meta_list, 0);
> +		meta->lba = cpu_to_le64(ADDR_EMPTY);
> +
>   		return;
>   	}
>   
> @@ -408,7 +421,9 @@ static void pblk_read_rq(struct pblk *pblk, struct nvm_rq *rqd, struct bio *bio,
>   		}
>   
>   		WARN_ON(test_and_set_bit(0, read_bitmap));
> -		meta_list[0].lba = cpu_to_le64(lba);
> +
> +		meta = sec_meta_index(pblk, rqd->meta_list, 0);
> +		meta->lba = cpu_to_le64(lba);
>   
>   #ifdef CONFIG_NVM_PBLK_DEBUG
>   		atomic_long_inc(&pblk->cache_reads);
> diff --git a/drivers/lightnvm/pblk-recovery.c b/drivers/lightnvm/pblk-recovery.c
> index 8114013c37b8..1ce92562603d 100644
> --- a/drivers/lightnvm/pblk-recovery.c
> +++ b/drivers/lightnvm/pblk-recovery.c
> @@ -157,7 +157,7 @@ static int pblk_recov_pad_line(struct pblk *pblk, struct pblk_line *line,
>   {
>   	struct nvm_tgt_dev *dev = pblk->dev;
>   	struct nvm_geo *geo = &dev->geo;
> -	struct pblk_sec_meta *meta_list;
> +	struct pblk_sec_meta *meta;
>   	struct pblk_pad_rq *pad_rq;
>   	struct nvm_rq *rqd;
>   	struct bio *bio;
> @@ -218,8 +218,6 @@ static int pblk_recov_pad_line(struct pblk *pblk, struct pblk_line *line,
>   	rqd->end_io = pblk_end_io_recov;
>   	rqd->private = pad_rq;
>   
> -	meta_list = rqd->meta_list;
> -
>   	for (i = 0; i < rqd->nr_ppas; ) {
>   		struct ppa_addr ppa;
>   		int pos;
> @@ -241,8 +239,10 @@ static int pblk_recov_pad_line(struct pblk *pblk, struct pblk_line *line,
>   			dev_ppa = addr_to_gen_ppa(pblk, w_ptr, line->id);
>   
>   			pblk_map_invalidate(pblk, dev_ppa);
> -			lba_list[w_ptr] = meta_list[i].lba = addr_empty;
>   			rqd->ppa_list[i] = dev_ppa;
> +
> +			meta = sec_meta_index(pblk, rqd->meta_list, i);
> +			lba_list[w_ptr] = meta->lba = addr_empty;
>   		}
>   	}
>   
> @@ -327,7 +327,7 @@ static int pblk_recov_scan_oob(struct pblk *pblk, struct pblk_line *line,
>   	struct nvm_tgt_dev *dev = pblk->dev;
>   	struct nvm_geo *geo = &dev->geo;
>   	struct ppa_addr *ppa_list;
> -	struct pblk_sec_meta *meta_list;
> +	struct pblk_sec_meta *meta_list, *meta;
>   	struct nvm_rq *rqd;
>   	struct bio *bio;
>   	void *data;
> @@ -425,7 +425,10 @@ static int pblk_recov_scan_oob(struct pblk *pblk, struct pblk_line *line,
>   	}
>   
>   	for (i = 0; i < rqd->nr_ppas; i++) {
> -		u64 lba = le64_to_cpu(meta_list[i].lba);
> +		u64 lba;
> +
> +		meta = sec_meta_index(pblk, meta_list, i);
> +		lba = le64_to_cpu(meta->lba);
>   
>   		lba_list[paddr++] = cpu_to_le64(lba);
>   
> @@ -464,13 +467,22 @@ static int pblk_recov_l2p_from_oob(struct pblk *pblk, struct pblk_line *line)
>   	if (!meta_list)
>   		return -ENOMEM;
>   
> -	ppa_list = (void *)(meta_list) + pblk_dma_meta_size;
> -	dma_ppa_list = dma_meta_list + pblk_dma_meta_size;
> +	if (pblk->dma_shared) {
> +		ppa_list = (void *)(meta_list) + pblk->dma_meta_size;
> +		dma_ppa_list = dma_meta_list + pblk->dma_meta_size;
> +	} else {
> +		ppa_list = nvm_dev_dma_alloc(dev->parent, GFP_KERNEL,
> +							&dma_ppa_list);
> +		if (!ppa_list) {
> +			ret = -ENOMEM;
> +			goto free_meta_list;
> +		}
> +	}
>   
>   	data = kcalloc(pblk->max_write_pgs, geo->csecs, GFP_KERNEL);
>   	if (!data) {
>   		ret = -ENOMEM;
> -		goto free_meta_list;
> +		goto free_ppa_list;
>   	}
>   
>   	rqd = mempool_alloc(&pblk->r_rq_pool, GFP_KERNEL);
> @@ -495,9 +507,11 @@ static int pblk_recov_l2p_from_oob(struct pblk *pblk, struct pblk_line *line)
>   out:
>   	mempool_free(rqd, &pblk->r_rq_pool);
>   	kfree(data);
> +free_ppa_list:
> +	if (!pblk->dma_shared)
> +		nvm_dev_dma_free(dev->parent, ppa_list, dma_ppa_list);
>   free_meta_list:
>   	nvm_dev_dma_free(dev->parent, meta_list, dma_meta_list);
> -
>   	return ret;
>   }
>   
> diff --git a/drivers/lightnvm/pblk.h b/drivers/lightnvm/pblk.h
> index 22cc9bfbbb10..4526fee206d9 100644
> --- a/drivers/lightnvm/pblk.h
> +++ b/drivers/lightnvm/pblk.h
> @@ -86,7 +86,6 @@ enum {
>   };
>   
>   struct pblk_sec_meta {
> -	u64 reserved;
>   	__le64 lba;
>   };
>   
> @@ -103,9 +102,6 @@ enum {
>   	PBLK_RL_LOW = 4
>   };
>   
> -#define pblk_dma_meta_size (sizeof(struct pblk_sec_meta) * NVM_MAX_VLBA)
> -#define pblk_dma_ppa_size (sizeof(u64) * NVM_MAX_VLBA)
> -
>   /* write buffer completion context */
>   struct pblk_c_ctx {
>   	struct list_head list;		/* Head for out-of-order completion */
> @@ -637,6 +633,10 @@ struct pblk {
>   
>   	int sec_per_write;
>   
> +	int dma_meta_size;
> +	int dma_ppa_size;
> +	bool dma_shared;
> +
>   	unsigned char instance_uuid[16];
>   
>   	/* Persistent write amplification counters, 4kb sector I/Os */
> @@ -985,6 +985,16 @@ static inline void *emeta_to_vsc(struct pblk *pblk, struct line_emeta *emeta)
>   	return (emeta_to_lbas(pblk, emeta) + pblk->lm.emeta_len[2]);
>   }
>   
> +static inline struct pblk_sec_meta *sec_meta_index(struct pblk *pblk,
> +						   struct pblk_sec_meta *meta,
> +						   int index)
> +{
> +	struct nvm_tgt_dev *dev = pblk->dev;
> +	struct nvm_geo *geo = &dev->geo;
> +
> +	return ((void *)meta + index * geo->sos);
> +}
> +
>   static inline int pblk_line_vsc(struct pblk_line *line)
>   {
>   	return le32_to_cpu(*line->vsc);
> 

It will be helpful to split this patch into two:

- One that does the 8b conversion
- One that makes the change to merge metadata and ppa list data buffers
   - How about making it a simplification to only allow up to 32b 
metadata buffers, then one doesn't have to think about it crossing 
multiple pages.
   - You can also make a structure for it, use the first 3.5KB for meta, 
and the next 512B for PPAs.