lightnvm: pblk: advance bio according to lba index

When a lba either hits the cache or corresponds to an empty entry in the
L2P table, we need to advance the bio according to the position in which
the lba is located. Otherwise, we will copy data in the wrong page, thus
causing data corruption for the application.

In case of a cache hit, we assumed that bio->bi_iter.bi_idx would
contain the correct index, but this is no necessarily true. Instead, use
the local bio advance counter and iterator. This guarantees that lbas
hitting the cache are copied into the right bv_page.

In case of an empty L2P entry, we omitted to advance the bio. In the
cases when the same I/O also contains a cache hit, data corresponding
to this lba will be copied to the wrong bv_page. Fix this by advancing
the bio as we do in the case of a cache hit.

Fixes: a4bd217b4326 lightnvm: physical block device (pblk) target

Signed-off-by: Javier González <javier@javigon.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 16 insertions, 7 deletions

diff --git a/drivers/lightnvm/pblk-read.c b/drivers/lightnvm/pblk-read.c
index 4e5c48f3de62..d682e89e6493 100644
--- a/drivers/lightnvm/pblk-read.c
+++ b/drivers/lightnvm/pblk-read.c
@@ -26,7 +26,7 @@
  */
 static int pblk_read_from_cache(struct pblk *pblk, struct bio *bio,
 				sector_t lba, struct ppa_addr ppa,
-				int bio_iter)
+				int bio_iter, bool advanced_bio)
 {
 #ifdef CONFIG_NVM_DEBUG
 	/* Callers must ensure that the ppa points to a cache address */
@@ -34,7 +34,8 @@ static int pblk_read_from_cache(struct pblk *pblk, struct bio *bio,
 	BUG_ON(!pblk_addr_in_cache(ppa));
 #endif
 
-	return pblk_rb_copy_to_bio(&pblk->rwb, bio, lba, ppa, bio_iter);
+	return pblk_rb_copy_to_bio(&pblk->rwb, bio, lba, ppa,
+						bio_iter, advanced_bio);
 }
 
 static void pblk_read_ppalist_rq(struct pblk *pblk, struct nvm_rq *rqd,
@@ -44,7 +45,7 @@ static void pblk_read_ppalist_rq(struct pblk *pblk, struct nvm_rq *rqd,
 	struct ppa_addr ppas[PBLK_MAX_REQ_ADDRS];
 	sector_t blba = pblk_get_lba(bio);
 	int nr_secs = rqd->nr_ppas;
-	int advanced_bio = 0;
+	bool advanced_bio = false;
 	int i, j = 0;
 
 	/* logic error: lba out-of-bounds. Ignore read request */
@@ -62,19 +63,26 @@ static void pblk_read_ppalist_rq(struct pblk *pblk, struct nvm_rq *rqd,
 retry:
 		if (pblk_ppa_empty(p)) {
 			WARN_ON(test_and_set_bit(i, read_bitmap));
-			continue;
+
+			if (unlikely(!advanced_bio)) {
+				bio_advance(bio, (i) * PBLK_EXPOSED_PAGE_SIZE);
+				advanced_bio = true;
+			}
+
+			goto next;
 		}
 
 		/* Try to read from write buffer. The address is later checked
 		 * on the write buffer to prevent retrieving overwritten data.
 		 */
 		if (pblk_addr_in_cache(p)) {
-			if (!pblk_read_from_cache(pblk, bio, lba, p, i)) {
+			if (!pblk_read_from_cache(pblk, bio, lba, p, i,
+								advanced_bio)) {
 				pblk_lookup_l2p_seq(pblk, &p, lba, 1);
 				goto retry;
 			}
 			WARN_ON(test_and_set_bit(i, read_bitmap));
-			advanced_bio = 1;
+			advanced_bio = true;
 #ifdef CONFIG_NVM_DEBUG
 			atomic_long_inc(&pblk->cache_reads);
 #endif
@@ -83,6 +91,7 @@ retry:
 			rqd->ppa_list[j++] = p;
 		}
 
+next:
 		if (advanced_bio)
 			bio_advance(bio, PBLK_EXPOSED_PAGE_SIZE);
 	}
@@ -282,7 +291,7 @@ retry:
 	 * write buffer to prevent retrieving overwritten data.
 	 */
 	if (pblk_addr_in_cache(ppa)) {
-		if (!pblk_read_from_cache(pblk, bio, lba, ppa, 0)) {
+		if (!pblk_read_from_cache(pblk, bio, lba, ppa, 0, 1)) {
 			pblk_lookup_l2p_seq(pblk, &ppa, lba, 1);
 			goto retry;
 		}