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, 53 insertions, 18 deletions

diff --git a/drivers/lightnvm/pblk-read.c b/drivers/lightnvm/pblk-read.c
index a465d9980df4..402f8eff6a2e 100644
--- a/drivers/lightnvm/pblk-read.c
+++ b/drivers/lightnvm/pblk-read.c
@@ -130,9 +130,34 @@ static void pblk_read_check(struct pblk *pblk, struct nvm_rq *rqd,
 	}
 }
 
-static void pblk_end_io_read(struct nvm_rq *rqd)
+static void pblk_read_put_rqd_kref(struct pblk *pblk, struct nvm_rq *rqd)
+{
+	struct ppa_addr *ppa_list;
+	int i;
+
+	ppa_list = (rqd->nr_ppas > 1) ? rqd->ppa_list : &rqd->ppa_addr;
+
+	for (i = 0; i < rqd->nr_ppas; i++) {
+		struct ppa_addr ppa = ppa_list[i];
+		struct pblk_line *line;
+
+		line = &pblk->lines[pblk_dev_ppa_to_line(ppa)];
+		kref_put(&line->ref, pblk_line_put_wq);
+	}
+}
+
+static void pblk_end_user_read(struct bio *bio)
+{
+#ifdef CONFIG_NVM_DEBUG
+	WARN_ONCE(bio->bi_status, "pblk: corrupted read bio\n");
+#endif
+	bio_endio(bio);
+	bio_put(bio);
+}
+
+static void __pblk_end_io_read(struct pblk *pblk, struct nvm_rq *rqd,
+			       bool put_line)
 {
-	struct pblk *pblk = rqd->private;
 	struct pblk_g_ctx *r_ctx = nvm_rq_to_pdu(rqd);
 	struct bio *bio = rqd->bio;
 
@@ -146,15 +171,11 @@ static void pblk_end_io_read(struct nvm_rq *rqd)
 	pblk_read_check(pblk, rqd, r_ctx->lba);
 
 	bio_put(bio);
-	if (r_ctx->private) {
-		struct bio *orig_bio = r_ctx->private;
+	if (r_ctx->private)
+		pblk_end_user_read((struct bio *)r_ctx->private);
 
-#ifdef CONFIG_NVM_DEBUG
-		WARN_ONCE(orig_bio->bi_status, "pblk: corrupted read bio\n");
-#endif
-		bio_endio(orig_bio);
-		bio_put(orig_bio);
-	}
+	if (put_line)
+		pblk_read_put_rqd_kref(pblk, rqd);
 
 #ifdef CONFIG_NVM_DEBUG
 	atomic_long_add(rqd->nr_ppas, &pblk->sync_reads);
@@ -165,6 +186,13 @@ static void pblk_end_io_read(struct nvm_rq *rqd)
 	atomic_dec(&pblk->inflight_io);
 }
 
+static void pblk_end_io_read(struct nvm_rq *rqd)
+{
+	struct pblk *pblk = rqd->private;
+
+	__pblk_end_io_read(pblk, rqd, true);
+}
+
 static int pblk_fill_partial_read_bio(struct pblk *pblk, struct nvm_rq *rqd,
 				      unsigned int bio_init_idx,
 				      unsigned long *read_bitmap)
@@ -233,8 +261,12 @@ static int pblk_fill_partial_read_bio(struct pblk *pblk, struct nvm_rq *rqd,
 	}
 
 	if (unlikely(nr_secs > 1 && nr_holes == 1)) {
+		struct ppa_addr ppa;
+
+		ppa = rqd->ppa_addr;
 		rqd->ppa_list = ppa_ptr;
 		rqd->dma_ppa_list = dma_ppa_list;
+		rqd->ppa_list[0] = ppa;
 	}
 
 	for (i = 0; i < nr_secs; i++) {
@@ -246,6 +278,11 @@ static int pblk_fill_partial_read_bio(struct pblk *pblk, struct nvm_rq *rqd,
 	i = 0;
 	hole = find_first_zero_bit(read_bitmap, nr_secs);
 	do {
+		int line_id = pblk_dev_ppa_to_line(rqd->ppa_list[i]);
+		struct pblk_line *line = &pblk->lines[line_id];
+
+		kref_put(&line->ref, pblk_line_put);
+
 		meta_list[hole].lba = lba_list_media[i];
 
 		src_bv = new_bio->bi_io_vec[i++];
@@ -269,19 +306,17 @@ static int pblk_fill_partial_read_bio(struct pblk *pblk, struct nvm_rq *rqd,
 	bio_put(new_bio);
 
 	/* Complete the original bio and associated request */
+	bio_endio(bio);
 	rqd->bio = bio;
 	rqd->nr_ppas = nr_secs;
-	rqd->private = pblk;
 
-	bio_endio(bio);
-	pblk_end_io_read(rqd);
+	__pblk_end_io_read(pblk, rqd, false);
 	return NVM_IO_OK;
 
 err:
 	/* Free allocated pages in new bio */
 	pblk_bio_free_pages(pblk, bio, 0, new_bio->bi_vcnt);
-	rqd->private = pblk;
-	pblk_end_io_read(rqd);
+	__pblk_end_io_read(pblk, rqd, false);
 	return NVM_IO_ERR;
 }
 
@@ -314,11 +349,11 @@ retry:
 			goto retry;
 		}
 
+		WARN_ON(test_and_set_bit(0, read_bitmap));
 		meta_list[0].lba = cpu_to_le64(lba);
 
-		WARN_ON(test_and_set_bit(0, read_bitmap));
 #ifdef CONFIG_NVM_DEBUG
-			atomic_long_inc(&pblk->cache_reads);
+		atomic_long_inc(&pblk->cache_reads);
 #endif
 	} else {
 		rqd->ppa_addr = ppa;
@@ -383,7 +418,7 @@ int pblk_submit_read(struct pblk *pblk, struct bio *bio)
 	if (bitmap_full(&read_bitmap, nr_secs)) {
 		bio_endio(bio);
 		atomic_inc(&pblk->inflight_io);
-		pblk_end_io_read(rqd);
+		__pblk_end_io_read(pblk, rqd, false);
 		return NVM_IO_OK;
 	}