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Commit 1e82123d authored by Javier González's avatar Javier González Committed by Jens Axboe
Browse files

lightnvm: pblk: remove I/O dependency on write path 



pblk schedules user I/O, metadata I/O and erases on the write path in
order to minimize collisions at the media level. Until now, there has
been a dependency between user and metadata I/Os that could lead to a
deadlock as both take the per-LUN semaphore to schedule submission.

This path removes this dependency and guarantees forward progress at a
per I/O granurality.

Signed-off-by: default avatarJavier González <javier@cnexlabs.com>
Signed-off-by: default avatarMatias Bjørling <m@bjorling.me>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 0f9248cf

drivers/lightnvm/pblk-write.c

+65 −80
Original line number Diff line number Diff line
@@ -220,15 +220,16 @@ static int pblk_alloc_w_rq(struct pblk *pblk, struct nvm_rq *rqd, 
}



static int pblk_setup_w_rq(struct pblk *pblk, struct nvm_rq *rqd,

			   struct pblk_c_ctx *c_ctx, struct ppa_addr *erase_ppa)

			   struct ppa_addr *erase_ppa)

{

	struct pblk_line_meta *lm = &pblk->lm;

	struct pblk_line *e_line = pblk_line_get_erase(pblk);

	struct pblk_c_ctx *c_ctx = nvm_rq_to_pdu(rqd);

	unsigned int valid = c_ctx->nr_valid;

	unsigned int padded = c_ctx->nr_padded;

	unsigned int nr_secs = valid + padded;

	unsigned long *lun_bitmap;

	int ret = 0;

	int ret;



	lun_bitmap = kzalloc(lm->lun_bitmap_len, GFP_KERNEL);

	if (!lun_bitmap)
@@ -294,55 +295,6 @@ static int pblk_calc_secs_to_sync(struct pblk *pblk, unsigned int secs_avail, 
	return secs_to_sync;

}



static inline int pblk_valid_meta_ppa(struct pblk *pblk,

				      struct pblk_line *meta_line,

				      struct ppa_addr *ppa_list, int nr_ppas)

{

	struct nvm_tgt_dev *dev = pblk->dev;

	struct nvm_geo *geo = &dev->geo;

	struct pblk_line *data_line;

	struct ppa_addr ppa, ppa_opt;

	u64 paddr;

	int i;



	data_line = &pblk->lines[pblk_dev_ppa_to_line(ppa_list[0])];

	paddr = pblk_lookup_page(pblk, meta_line);

	ppa = addr_to_gen_ppa(pblk, paddr, 0);



	if (test_bit(pblk_ppa_to_pos(geo, ppa), data_line->blk_bitmap))

		return 1;



	/* Schedule a metadata I/O that is half the distance from the data I/O

	 * with regards to the number of LUNs forming the pblk instance. This

	 * balances LUN conflicts across every I/O.

	 *

	 * When the LUN configuration changes (e.g., due to GC), this distance

	 * can align, which would result on a LUN deadlock. In this case, modify

	 * the distance to not be optimal, but allow metadata I/Os to succeed.

	 */

	ppa_opt = addr_to_gen_ppa(pblk, paddr + data_line->meta_distance, 0);

	if (unlikely(ppa_opt.ppa == ppa.ppa)) {

		data_line->meta_distance--;

		return 0;

	}



	for (i = 0; i < nr_ppas; i += pblk->min_write_pgs)

		if (ppa_list[i].g.ch == ppa_opt.g.ch &&

					ppa_list[i].g.lun == ppa_opt.g.lun)

			return 1;



	if (test_bit(pblk_ppa_to_pos(geo, ppa_opt), data_line->blk_bitmap)) {

		for (i = 0; i < nr_ppas; i += pblk->min_write_pgs)

			if (ppa_list[i].g.ch == ppa.g.ch &&

						ppa_list[i].g.lun == ppa.g.lun)

				return 0;



		return 1;

	}



	return 0;

}



int pblk_submit_meta_io(struct pblk *pblk, struct pblk_line *meta_line)

{

	struct nvm_tgt_dev *dev = pblk->dev;
@@ -421,8 +373,44 @@ int pblk_submit_meta_io(struct pblk *pblk, struct pblk_line *meta_line) 
	return ret;

}



static int pblk_sched_meta_io(struct pblk *pblk, struct ppa_addr *prev_list,

			       int prev_n)

static inline bool pblk_valid_meta_ppa(struct pblk *pblk,

				       struct pblk_line *meta_line,

				       struct nvm_rq *data_rqd)

{

	struct nvm_tgt_dev *dev = pblk->dev;

	struct nvm_geo *geo = &dev->geo;

	struct pblk_c_ctx *data_c_ctx = nvm_rq_to_pdu(data_rqd);

	struct pblk_line *data_line = pblk_line_get_data(pblk);

	struct ppa_addr ppa, ppa_opt;

	u64 paddr;

	int pos_opt;



	/* Schedule a metadata I/O that is half the distance from the data I/O

	 * with regards to the number of LUNs forming the pblk instance. This

	 * balances LUN conflicts across every I/O.

	 *

	 * When the LUN configuration changes (e.g., due to GC), this distance

	 * can align, which would result on metadata and data I/Os colliding. In

	 * this case, modify the distance to not be optimal, but move the

	 * optimal in the right direction.

	 */

	paddr = pblk_lookup_page(pblk, meta_line);

	ppa = addr_to_gen_ppa(pblk, paddr, 0);

	ppa_opt = addr_to_gen_ppa(pblk, paddr + data_line->meta_distance, 0);

	pos_opt = pblk_ppa_to_pos(geo, ppa_opt);



	if (test_bit(pos_opt, data_c_ctx->lun_bitmap) ||

				test_bit(pos_opt, data_line->blk_bitmap))

		return true;



	if (unlikely(pblk_ppa_comp(ppa_opt, ppa)))

		data_line->meta_distance--;



	return false;

}



static struct pblk_line *pblk_should_submit_meta_io(struct pblk *pblk,

						    struct nvm_rq *data_rqd)

{

	struct pblk_line_meta *lm = &pblk->lm;

	struct pblk_line_mgmt *l_mg = &pblk->l_mg;
@@ -432,41 +420,35 @@ static int pblk_sched_meta_io(struct pblk *pblk, struct ppa_addr *prev_list, 
retry:

	if (list_empty(&l_mg->emeta_list)) {

		spin_unlock(&l_mg->close_lock);

		return 0;

		return NULL;

	}

	meta_line = list_first_entry(&l_mg->emeta_list, struct pblk_line, list);

	if (meta_line->emeta->mem >= lm->emeta_len[0])

		goto retry;

	spin_unlock(&l_mg->close_lock);



	if (!pblk_valid_meta_ppa(pblk, meta_line, prev_list, prev_n))

		return 0;

	if (!pblk_valid_meta_ppa(pblk, meta_line, data_rqd))

		return NULL;



	return pblk_submit_meta_io(pblk, meta_line);

	return meta_line;

}



static int pblk_submit_io_set(struct pblk *pblk, struct nvm_rq *rqd)

{

	struct pblk_c_ctx *c_ctx = nvm_rq_to_pdu(rqd);

	struct ppa_addr erase_ppa;

	struct pblk_line *meta_line;

	int err;



	ppa_set_empty(&erase_ppa);



	/* Assign lbas to ppas and populate request structure */

	err = pblk_setup_w_rq(pblk, rqd, c_ctx, &erase_ppa);

	err = pblk_setup_w_rq(pblk, rqd, &erase_ppa);

	if (err) {

		pr_err("pblk: could not setup write request: %d\n", err);

		return NVM_IO_ERR;

	}



	if (likely(ppa_empty(erase_ppa))) {

		/* Submit metadata write for previous data line */

		err = pblk_sched_meta_io(pblk, rqd->ppa_list, rqd->nr_ppas);

		if (err) {

			pr_err("pblk: metadata I/O submission failed: %d", err);

			return NVM_IO_ERR;

		}

	meta_line = pblk_should_submit_meta_io(pblk, rqd);



	/* Submit data write for current data line */

	err = pblk_submit_io(pblk, rqd);
@@ -474,15 +456,9 @@ static int pblk_submit_io_set(struct pblk *pblk, struct nvm_rq *rqd) 
		pr_err("pblk: data I/O submission failed: %d\n", err);

		return NVM_IO_ERR;

	}

	} else {

		/* Submit data write for current data line */

		err = pblk_submit_io(pblk, rqd);

		if (err) {

			pr_err("pblk: data I/O submission failed: %d\n", err);

			return NVM_IO_ERR;

		}



		/* Submit available erase for next data line */

	if (!ppa_empty(erase_ppa)) {

		/* Submit erase for next data line */

		if (pblk_blk_erase_async(pblk, erase_ppa)) {

			struct pblk_line *e_line = pblk_line_get_erase(pblk);

			struct nvm_tgt_dev *dev = pblk->dev;
@@ -495,6 +471,15 @@ static int pblk_submit_io_set(struct pblk *pblk, struct nvm_rq *rqd) 
		}

	}



	if (meta_line) {

		/* Submit metadata write for previous data line */

		err = pblk_submit_meta_io(pblk, meta_line);

		if (err) {

			pr_err("pblk: metadata I/O submission failed: %d", err);

			return NVM_IO_ERR;

		}

	}



	return NVM_IO_OK;

}