Commit 0586942f authored by Heiner Litz's avatar Heiner Litz Committed by Jens Axboe
Browse files

lightnvm: pblk: fix race condition on GC 



This patch fixes a race condition where a write is mapped to the last
sectors of a line. The write is synced to the device but the L2P is not
updated yet. When the line is garbage collected before the L2P update
is performed, the sectors are ignored by the GC logic and the line is
freed before all sectors are moved. When the L2P is finally updated, it
contains a mapping to a freed line, subsequent reads of the
corresponding LBAs fail.

This patch introduces a per line counter specifying the number of
sectors that are synced to the device but have not been updated in the
L2P. Lines with a counter of greater than zero will not be selected
for GC.

Signed-off-by: default avatarHeiner Litz <hlitz@ucsc.edu>
Reviewed-by: default avatarHans Holmberg <hans.holmberg@cnexlabs.com>
Reviewed-by: default avatarJavier González <javier@javigon.com>
Signed-off-by: default avatarMatias Bjørling <mb@lightnvm.io>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent b4cdc426

drivers/lightnvm/pblk-core.c

+1 −0
Original line number Diff line number Diff line
@@ -1278,6 +1278,7 @@ static int pblk_line_prepare(struct pblk *pblk, struct pblk_line *line) 
	spin_unlock(&line->lock);



	kref_init(&line->ref);

	atomic_set(&line->sec_to_update, 0);



	return 0;

}

drivers/lightnvm/pblk-gc.c

+13 −7
Original line number Diff line number Diff line
@@ -365,15 +365,21 @@ static struct pblk_line *pblk_gc_get_victim_line(struct pblk *pblk, 
						 struct list_head *group_list)

{

	struct pblk_line *line, *victim;

	int line_vsc, victim_vsc;

	unsigned int line_vsc = ~0x0L, victim_vsc = ~0x0L;



	victim = list_first_entry(group_list, struct pblk_line, list);



	list_for_each_entry(line, group_list, list) {

		if (!atomic_read(&line->sec_to_update))

			line_vsc = le32_to_cpu(*line->vsc);

		victim_vsc = le32_to_cpu(*victim->vsc);

		if (line_vsc < victim_vsc)

		if (line_vsc < victim_vsc) {

			victim = line;

			victim_vsc = le32_to_cpu(*victim->vsc);

		}

	}



	if (victim_vsc == ~0x0)

		return NULL;



	return victim;

}
@@ -448,13 +454,13 @@ next_gc_group: 


	do {

		spin_lock(&l_mg->gc_lock);

		if (list_empty(group_list)) {



		line = pblk_gc_get_victim_line(pblk, group_list);

		if (!line) {

			spin_unlock(&l_mg->gc_lock);

			break;

		}



		line = pblk_gc_get_victim_line(pblk, group_list);



		spin_lock(&line->lock);

		WARN_ON(line->state != PBLK_LINESTATE_CLOSED);

		line->state = PBLK_LINESTATE_GC;

drivers/lightnvm/pblk-map.c

+1 −0
Original line number Diff line number Diff line
@@ -73,6 +73,7 @@ static int pblk_map_page_data(struct pblk *pblk, unsigned int sentry, 
		 */

		if (i < valid_secs) {

			kref_get(&line->ref);

			atomic_inc(&line->sec_to_update);

			w_ctx = pblk_rb_w_ctx(&pblk->rwb, sentry + i);

			w_ctx->ppa = ppa_list[i];

			meta->lba = cpu_to_le64(w_ctx->lba);

drivers/lightnvm/pblk-rb.c

+1 −0
Original line number Diff line number Diff line
@@ -260,6 +260,7 @@ static int __pblk_rb_update_l2p(struct pblk_rb *rb, unsigned int to_update) 
							entry->cacheline);



		line = pblk_ppa_to_line(pblk, w_ctx->ppa);

		atomic_dec(&line->sec_to_update);

		kref_put(&line->ref, pblk_line_put);

		clean_wctx(w_ctx);

		rb->l2p_update = pblk_rb_ptr_wrap(rb, rb->l2p_update, 1);

drivers/lightnvm/pblk-write.c

+1 −0
Original line number Diff line number Diff line
@@ -177,6 +177,7 @@ static void pblk_prepare_resubmit(struct pblk *pblk, unsigned int sentry, 
		 * re-map these entries

		 */

		line = pblk_ppa_to_line(pblk, w_ctx->ppa);

		atomic_dec(&line->sec_to_update);

		kref_put(&line->ref, pblk_line_put);

	}

	spin_unlock(&pblk->trans_lock);

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