[PATCH] lightnvm: pblk: check lba sanity on read path

["Javier González" <jg@lightnvm.io>]

As part of pblk's recovery scheme, we store the lba mapped to each
physical sector on the device's out-of-bound (OOB) area.

On the read path, we can use this information to validate that the data
being delivered to the upper layers corresponds to the lba being
requested. The cost of this check is an extra copy on the DMA region on
the device and an extra comparison in the host, given that (i) the OOB
area is being read together with the data in the media, and (ii) the DMA
region allocated for the ppa list can be reused for the metadata stored
on the OOB area.

Signed-off-by: Javier González <javier@cnexlabs.com>
---
 drivers/lightnvm/pblk-read.c | 51 +++++++++++++++++++++++++++++++++++++++++---
 drivers/lightnvm/pblk.h      |  4 +++-
 2 files changed, 51 insertions(+), 4 deletions(-)

diff --git a/drivers/lightnvm/pblk-read.c b/drivers/lightnvm/pblk-read.c
index 0299fc08291d..a465d9980df4 100644
--- a/drivers/lightnvm/pblk-read.c
+++ b/drivers/lightnvm/pblk-read.c
@@ -41,6 +41,7 @@ static int pblk_read_from_cache(struct pblk *pblk, struct bio *bio,
 static void pblk_read_ppalist_rq(struct pblk *pblk, struct nvm_rq *rqd,
 				 sector_t blba, unsigned long *read_bitmap)
 {
+	struct pblk_sec_meta *meta_list = rqd->meta_list;
 	struct bio *bio = rqd->bio;
 	struct ppa_addr ppas[PBLK_MAX_REQ_ADDRS];
 	int nr_secs = rqd->nr_ppas;
@@ -56,6 +57,7 @@ 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));
+			meta_list[i].lba = cpu_to_le64(ADDR_EMPTY);
 
 			if (unlikely(!advanced_bio)) {
 				bio_advance(bio, (i) * PBLK_EXPOSED_PAGE_SIZE);
@@ -75,6 +77,7 @@ static void pblk_read_ppalist_rq(struct pblk *pblk, struct nvm_rq *rqd,
 				goto retry;
 			}
 			WARN_ON(test_and_set_bit(i, read_bitmap));
+			meta_list[i].lba = cpu_to_le64(lba);
 			advanced_bio = true;
 #ifdef CONFIG_NVM_DEBUG
 			atomic_long_inc(&pblk->cache_reads);
@@ -110,10 +113,26 @@ static int pblk_submit_read_io(struct pblk *pblk, struct nvm_rq *rqd)
 	return NVM_IO_OK;
 }
 
+static void pblk_read_check(struct pblk *pblk, struct nvm_rq *rqd,
+			   sector_t blba)
+{
+	struct pblk_sec_meta *meta_list = rqd->meta_list;
+	int nr_lbas = rqd->nr_ppas;
+	int i;
+
+	for (i = 0; i < nr_lbas; i++) {
+		u64 lba = le64_to_cpu(meta_list[i].lba);
+
+		if (lba == ADDR_EMPTY)
+			continue;
+
+		WARN(lba != blba + i, "pblk: corrupted read LBA\n");
+	}
+}
+
 static void pblk_end_io_read(struct nvm_rq *rqd)
 {
 	struct pblk *pblk = rqd->private;
-	struct nvm_tgt_dev *dev = pblk->dev;
 	struct pblk_g_ctx *r_ctx = nvm_rq_to_pdu(rqd);
 	struct bio *bio = rqd->bio;
 
@@ -124,6 +143,8 @@ static void pblk_end_io_read(struct nvm_rq *rqd)
 		WARN_ONCE(bio->bi_status, "pblk: corrupted read error\n");
 #endif
 
+	pblk_read_check(pblk, rqd, r_ctx->lba);
+
 	bio_put(bio);
 	if (r_ctx->private) {
 		struct bio *orig_bio = r_ctx->private;
@@ -149,15 +170,21 @@ static int pblk_fill_partial_read_bio(struct pblk *pblk, struct nvm_rq *rqd,
 				      unsigned long *read_bitmap)
 {
 	struct bio *new_bio, *bio = rqd->bio;
+	struct pblk_sec_meta *meta_list = rqd->meta_list;
 	struct bio_vec src_bv, dst_bv;
 	void *ppa_ptr = NULL;
 	void *src_p, *dst_p;
 	dma_addr_t dma_ppa_list = 0;
+	__le64 *lba_list_mem, *lba_list_media;
 	int nr_secs = rqd->nr_ppas;
 	int nr_holes = nr_secs - bitmap_weight(read_bitmap, nr_secs);
 	int i, ret, hole;
 	DECLARE_COMPLETION_ONSTACK(wait);
 
+	/* Re-use allocated memory for intermediate lbas */
+	lba_list_mem = (((void *)rqd->ppa_list) + pblk_dma_ppa_size);
+	lba_list_media = (((void *)rqd->ppa_list) + 2 * pblk_dma_ppa_size);
+
 	new_bio = bio_alloc(GFP_KERNEL, nr_holes);
 
 	if (pblk_bio_add_pages(pblk, new_bio, GFP_KERNEL, nr_holes))
@@ -168,6 +195,9 @@ static int pblk_fill_partial_read_bio(struct pblk *pblk, struct nvm_rq *rqd,
 		goto err;
 	}
 
+	for (i = 0; i < nr_secs; i++)
+		lba_list_mem[i] = meta_list[i].lba;
+
 	new_bio->bi_iter.bi_sector = 0; /* internal bio */
 	bio_set_op_attrs(new_bio, REQ_OP_READ, 0);
 
@@ -207,10 +237,17 @@ static int pblk_fill_partial_read_bio(struct pblk *pblk, struct nvm_rq *rqd,
 		rqd->dma_ppa_list = dma_ppa_list;
 	}
 
+	for (i = 0; i < nr_secs; i++) {
+		lba_list_media[i] = meta_list[i].lba;
+		meta_list[i].lba = lba_list_mem[i];
+	}
+
 	/* Fill the holes in the original bio */
 	i = 0;
 	hole = find_first_zero_bit(read_bitmap, nr_secs);
 	do {
+		meta_list[hole].lba = lba_list_media[i];
+
 		src_bv = new_bio->bi_io_vec[i++];
 		dst_bv = bio->bi_io_vec[bio_init_idx + hole];
 
@@ -251,6 +288,7 @@ static int pblk_fill_partial_read_bio(struct pblk *pblk, struct nvm_rq *rqd,
 static void pblk_read_rq(struct pblk *pblk, struct nvm_rq *rqd,
 			 sector_t lba, unsigned long *read_bitmap)
 {
+	struct pblk_sec_meta *meta_list = rqd->meta_list;
 	struct bio *bio = rqd->bio;
 	struct ppa_addr ppa;
 
@@ -263,6 +301,7 @@ static void pblk_read_rq(struct pblk *pblk, struct nvm_rq *rqd,
 retry:
 	if (pblk_ppa_empty(ppa)) {
 		WARN_ON(test_and_set_bit(0, read_bitmap));
+		meta_list[0].lba = cpu_to_le64(ADDR_EMPTY);
 		return;
 	}
 
@@ -274,6 +313,9 @@ static void pblk_read_rq(struct pblk *pblk, struct nvm_rq *rqd,
 			pblk_lookup_l2p_seq(pblk, &ppa, lba, 1);
 			goto retry;
 		}
+
+		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);
@@ -290,9 +332,10 @@ int pblk_submit_read(struct pblk *pblk, struct bio *bio)
 	struct nvm_tgt_dev *dev = pblk->dev;
 	sector_t blba = pblk_get_lba(bio);
 	unsigned int nr_secs = pblk_get_secs(bio);
+	struct pblk_g_ctx *r_ctx;
 	struct nvm_rq *rqd;
-	unsigned long read_bitmap; /* Max 64 ppas per request */
 	unsigned int bio_init_idx;
+	unsigned long read_bitmap; /* Max 64 ppas per request */
 	int ret = NVM_IO_ERR;
 
 	/* logic error: lba out-of-bounds. Ignore read request */
@@ -312,6 +355,9 @@ int pblk_submit_read(struct pblk *pblk, struct bio *bio)
 	rqd->private = pblk;
 	rqd->end_io = pblk_end_io_read;
 
+	r_ctx = nvm_rq_to_pdu(rqd);
+	r_ctx->lba = blba;
+
 	/* Save the index for this bio's start. This is needed in case
 	 * we need to fill a partial read.
 	 */
@@ -344,7 +390,6 @@ int pblk_submit_read(struct pblk *pblk, struct bio *bio)
 	/* All sectors are to be read from the device */
 	if (bitmap_empty(&read_bitmap, rqd->nr_ppas)) {
 		struct bio *int_bio = NULL;
-		struct pblk_g_ctx *r_ctx = nvm_rq_to_pdu(rqd);
 
 		/* Clone read bio to deal with read errors internally */
 		int_bio = bio_clone_fast(bio, GFP_KERNEL, pblk_bio_set);
diff --git a/drivers/lightnvm/pblk.h b/drivers/lightnvm/pblk.h
index adae8620e298..ac65e778b40d 100644
--- a/drivers/lightnvm/pblk.h
+++ b/drivers/lightnvm/pblk.h
@@ -99,6 +99,7 @@ enum {
 };
 
 #define pblk_dma_meta_size (sizeof(struct pblk_sec_meta) * PBLK_MAX_REQ_ADDRS)
+#define pblk_dma_ppa_size (sizeof(u64) * PBLK_MAX_REQ_ADDRS)
 
 /* write buffer completion context */
 struct pblk_c_ctx {
@@ -110,9 +111,10 @@ struct pblk_c_ctx {
 	unsigned int nr_padded;
 };
 
-/* generic context */
+/* read context */
 struct pblk_g_ctx {
 	void *private;
+	u64 lba;
 };
 
 /* Pad context */
-- 
2.7.4