lightnvm: pblk: guarantee line integrity on reads

When a line is recycled during garbage collection, reads can still be
issued to the line. If the line is freed in the middle of this process,
data corruption might occur.

This patch guarantees that lines are not freed in the middle of reads
that target them (lines). Specifically, we use the existing line
reference to decide when a line is eligible for being freed after the
recycle process.

Signed-off-by: Javier González <javier@cnexlabs.com>
Signed-off-by: Matias Bjørling <m@bjorling.me>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 51 insertions, 5 deletions

diff --git a/drivers/lightnvm/pblk-core.c b/drivers/lightnvm/pblk-core.c
index 08d166ac4f3c..0a41fb998d55 100644
--- a/drivers/lightnvm/pblk-core.c
+++ b/drivers/lightnvm/pblk-core.c
@@ -1460,10 +1460,8 @@ void pblk_line_free(struct pblk *pblk, struct pblk_line *line)
 	line->emeta = NULL;
 }
 
-void pblk_line_put(struct kref *ref)
+static void __pblk_line_put(struct pblk *pblk, struct pblk_line *line)
 {
-	struct pblk_line *line = container_of(ref, struct pblk_line, ref);
-	struct pblk *pblk = line->pblk;
 	struct pblk_line_mgmt *l_mg = &pblk->l_mg;
 
 	spin_lock(&line->lock);
@@ -1481,6 +1479,43 @@ void pblk_line_put(struct kref *ref)
 	pblk_rl_free_lines_inc(&pblk->rl, line);
 }
 
+static void pblk_line_put_ws(struct work_struct *work)
+{
+	struct pblk_line_ws *line_put_ws = container_of(work,
+						struct pblk_line_ws, ws);
+	struct pblk *pblk = line_put_ws->pblk;
+	struct pblk_line *line = line_put_ws->line;
+
+	__pblk_line_put(pblk, line);
+	mempool_free(line_put_ws, pblk->gen_ws_pool);
+}
+
+void pblk_line_put(struct kref *ref)
+{
+	struct pblk_line *line = container_of(ref, struct pblk_line, ref);
+	struct pblk *pblk = line->pblk;
+
+	__pblk_line_put(pblk, line);
+}
+
+void pblk_line_put_wq(struct kref *ref)
+{
+	struct pblk_line *line = container_of(ref, struct pblk_line, ref);
+	struct pblk *pblk = line->pblk;
+	struct pblk_line_ws *line_put_ws;
+
+	line_put_ws = mempool_alloc(pblk->gen_ws_pool, GFP_ATOMIC);
+	if (!line_put_ws)
+		return;
+
+	line_put_ws->pblk = pblk;
+	line_put_ws->line = line;
+	line_put_ws->priv = NULL;
+
+	INIT_WORK(&line_put_ws->ws, pblk_line_put_ws);
+	queue_work(pblk->r_end_wq, &line_put_ws->ws);
+}
+
 int pblk_blk_erase_async(struct pblk *pblk, struct ppa_addr ppa)
 {
 	struct nvm_rq *rqd;
@@ -1878,8 +1913,19 @@ void pblk_lookup_l2p_seq(struct pblk *pblk, struct ppa_addr *ppas,
 	int i;
 
 	spin_lock(&pblk->trans_lock);
-	for (i = 0; i < nr_secs; i++)
-		ppas[i] = pblk_trans_map_get(pblk, blba + i);
+	for (i = 0; i < nr_secs; i++) {
+		struct ppa_addr ppa;
+
+		ppa = ppas[i] = pblk_trans_map_get(pblk, blba + i);
+
+		/* If the L2P entry maps to a line, the reference is valid */
+		if (!pblk_ppa_empty(ppa) && !pblk_addr_in_cache(ppa)) {
+			int line_id = pblk_dev_ppa_to_line(ppa);
+			struct pblk_line *line = &pblk->lines[line_id];
+
+			kref_get(&line->ref);
+		}
+	}
 	spin_unlock(&pblk->trans_lock);
 }