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Commit 21d22871 authored by Javier González's avatar Javier González Committed by Jens Axboe
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lightnvm: pblk: enable 1 LUN configuration 



Metadata I/Os are scheduled to minimize their impact on user data I/Os.
When there are enough LUNs instantiated (i.e., enough bandwidth), it is
easy to interleave metadata and data one after the other so that
metadata I/Os are the ones being blocked and not vice-versa.

We do this by calculating the distance between the I/Os in terms of the
LUNs that are not in used, and selecting a free LUN that satisfies a
the simple heuristic that metadata is scheduled behind. The per-LUN
semaphores guarantee consistency. This works fine on >1 LUN
configuration. However, when a single LUN is instantiated, this design
leads to a deadlock, where metadata waits to be scheduled on a free LUN.

This patch implements the 1 LUN case by simply scheduling the metadada
I/O after the data I/O. In the process, we refactor the way a line is
replaced to ensure that metadata writes are submitted after data writes
in order to guarantee block sequentiality. Note that, since there is
only one LUN, both I/Os will block each other by design. However, such
configuration only pursues tight read latencies, not write bandwidth.

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 1e82123d

drivers/lightnvm/pblk-core.c

+10 −7
Original line number Diff line number Diff line
@@ -1372,17 +1372,17 @@ void pblk_pipeline_stop(struct pblk *pblk) 
	spin_unlock(&l_mg->free_lock);

}



void pblk_line_replace_data(struct pblk *pblk)

struct pblk_line *pblk_line_replace_data(struct pblk *pblk)

{

	struct pblk_line_mgmt *l_mg = &pblk->l_mg;

	struct pblk_line *cur, *new;

	struct pblk_line *cur, *new = NULL;

	unsigned int left_seblks;

	int is_next = 0;



	cur = l_mg->data_line;

	new = l_mg->data_next;

	if (!new)

		return;

		goto out;

	l_mg->data_line = new;



	spin_lock(&l_mg->free_lock);
@@ -1390,7 +1390,7 @@ void pblk_line_replace_data(struct pblk *pblk) 
		l_mg->data_line = NULL;

		l_mg->data_next = NULL;

		spin_unlock(&l_mg->free_lock);

		return;

		goto out;

	}



	pblk_line_setup_metadata(new, l_mg, &pblk->lm);
@@ -1402,7 +1402,7 @@ void pblk_line_replace_data(struct pblk *pblk) 
		/* If line is not fully erased, erase it */

		if (atomic_read(&new->left_eblks)) {

			if (pblk_line_erase(pblk, new))

				return;

				goto out;

		} else {

			io_schedule();

		}
@@ -1413,7 +1413,7 @@ void pblk_line_replace_data(struct pblk *pblk) 
	if (!pblk_line_init_metadata(pblk, new, cur)) {

		new = pblk_line_retry(pblk, new);

		if (!new)

			return;

			goto out;



		goto retry_setup;

	}
@@ -1421,7 +1421,7 @@ void pblk_line_replace_data(struct pblk *pblk) 
	if (!pblk_line_init_bb(pblk, new, 1)) {

		new = pblk_line_retry(pblk, new);

		if (!new)

			return;

			goto out;



		goto retry_setup;

	}
@@ -1445,6 +1445,9 @@ void pblk_line_replace_data(struct pblk *pblk) 


	if (is_next)

		pblk_rl_free_lines_dec(&pblk->rl, l_mg->data_next);



out:

	return new;

}



void pblk_line_free(struct pblk *pblk, struct pblk_line *line)

drivers/lightnvm/pblk-init.c

+6 −2
Original line number Diff line number Diff line
@@ -711,8 +711,12 @@ static int pblk_lines_init(struct pblk *pblk) 
	}



	lm->emeta_bb = geo->nr_luns - i;

	lm->min_blk_line = 1 + DIV_ROUND_UP(lm->smeta_sec + lm->emeta_sec[0],

							geo->sec_per_blk);



	lm->min_blk_line = 1;

	if (geo->nr_luns > 1)

		lm->min_blk_line += DIV_ROUND_UP(lm->smeta_sec +

					lm->emeta_sec[0], geo->sec_per_blk);



	if (lm->min_blk_line > lm->blk_per_line) {

		pr_err("pblk: config. not supported. Min. LUN in line:%d\n",

							lm->blk_per_line);

drivers/lightnvm/pblk-map.c

+12 −9
Original line number Diff line number Diff line
@@ -25,13 +25,23 @@ static void 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_emeta *emeta = line->emeta;

	struct pblk_emeta *emeta;

	struct pblk_w_ctx *w_ctx;

	__le64 *lba_list = emeta_to_lbas(pblk, emeta->buf);

	__le64 *lba_list;

	u64 paddr;

	int nr_secs = pblk->min_write_pgs;

	int i;



	if (pblk_line_is_full(line)) {

		struct pblk_line *prev_line = line;



		line = pblk_line_replace_data(pblk);

		pblk_line_close_meta(pblk, prev_line);

	}



	emeta = line->emeta;

	lba_list = emeta_to_lbas(pblk, emeta->buf);



	paddr = pblk_alloc_page(pblk, line, nr_secs);



	for (i = 0; i < nr_secs; i++, paddr++) {
@@ -60,13 +70,6 @@ static void pblk_map_page_data(struct pblk *pblk, unsigned int sentry, 
		}

	}



	if (pblk_line_is_full(line)) {

		struct pblk_line *prev_line = line;



		pblk_line_replace_data(pblk);

		pblk_line_close_meta(pblk, prev_line);

	}



	pblk_down_rq(pblk, ppa_list, nr_secs, lun_bitmap);

}

drivers/lightnvm/pblk.h

+1 −1
Original line number Diff line number Diff line
@@ -719,7 +719,7 @@ struct bio *pblk_bio_map_addr(struct pblk *pblk, void *data, 
			      int alloc_type, gfp_t gfp_mask);

struct pblk_line *pblk_line_get(struct pblk *pblk);

struct pblk_line *pblk_line_get_first_data(struct pblk *pblk);

void pblk_line_replace_data(struct pblk *pblk);

struct pblk_line *pblk_line_replace_data(struct pblk *pblk);

int pblk_line_recov_alloc(struct pblk *pblk, struct pblk_line *line);

void pblk_line_recov_close(struct pblk *pblk, struct pblk_line *line);

struct pblk_line *pblk_line_get_data(struct pblk *pblk);