[PATCH v6 4/5] dm verity: Fix I/O priority lost when read FEC and hash

[Hongyu Jin]

From: Hongyu Jin <hongyu.jin@xxxxxxxxxx>

After obtaining the data, verification or error correction process may
trigger a new I/O that loses the priority of the original I/O, that is,
the verification of the higher priority IO may be blocked by the lower
priority IO.

Make the I/O of verification and error correction follow the
priority of original I/O.

Co-developed-by: Yibin Ding <yibin.ding@xxxxxxxxxx>
Signed-off-by: Yibin Ding <yibin.ding@xxxxxxxxxx>
Signed-off-by: Hongyu Jin <hongyu.jin@xxxxxxxxxx>
---
 drivers/md/dm-verity-fec.c    | 20 +++++++++++++++-----
 drivers/md/dm-verity-target.c | 12 ++++++++----
 2 files changed, 23 insertions(+), 9 deletions(-)

diff --git a/drivers/md/dm-verity-fec.c b/drivers/md/dm-verity-fec.c
index 49db19e537f9..a9e5402e3d43 100644
--- a/drivers/md/dm-verity-fec.c
+++ b/drivers/md/dm-verity-fec.c
@@ -18,6 +18,12 @@ bool verity_fec_is_enabled(struct dm_verity *v)
 	return v->fec && v->fec->dev;
 }
 
+static inline struct dm_verity_io *verity_io(struct dm_verity *v, struct dm_verity_fec_io *fio)
+{
+	return (struct dm_verity_io *)
+		((char *)fio + sizeof(struct dm_verity_fec_io) - v->ti->per_io_data_size);
+}
+
 /*
  * Return a pointer to dm_verity_fec_io after dm_verity_io and its variable
  * length fields.
@@ -60,7 +66,8 @@ static int fec_decode_rs8(struct dm_verity *v, struct dm_verity_fec_io *fio,
  * to the data block. Caller is responsible for releasing buf.
  */
 static u8 *fec_read_parity(struct dm_verity *v, u64 rsb, int index,
-			   unsigned int *offset, struct dm_buffer **buf)
+			   unsigned int *offset, struct dm_buffer **buf,
+			   unsigned short ioprio)
 {
 	u64 position, block, rem;
 	u8 *res;
@@ -69,7 +76,7 @@ static u8 *fec_read_parity(struct dm_verity *v, u64 rsb, int index,
 	block = div64_u64_rem(position, v->fec->io_size, &rem);
 	*offset = (unsigned int)rem;
 
-	res = dm_bufio_read(v->fec->bufio, block, buf, IOPRIO_DEFAULT);
+	res = dm_bufio_read(v->fec->bufio, block, buf, ioprio);
 	if (IS_ERR(res)) {
 		DMERR("%s: FEC %llu: parity read failed (block %llu): %ld",
 		      v->data_dev->name, (unsigned long long)rsb,
@@ -129,8 +136,10 @@ static int fec_decode_bufs(struct dm_verity *v, struct dm_verity_fec_io *fio,
 	struct dm_buffer *buf;
 	unsigned int n, i, offset;
 	u8 *par, *block;
+	struct dm_verity_io *io = verity_io(v, fio);
+	struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size);
 
-	par = fec_read_parity(v, rsb, block_offset, &offset, &buf);
+	par = fec_read_parity(v, rsb, block_offset, &offset, &buf, bio_prio(bio));
 	if (IS_ERR(par))
 		return PTR_ERR(par);
 
@@ -158,7 +167,7 @@ static int fec_decode_bufs(struct dm_verity *v, struct dm_verity_fec_io *fio,
 		if (offset >= v->fec->io_size) {
 			dm_bufio_release(buf);
 
-			par = fec_read_parity(v, rsb, block_offset, &offset, &buf);
+			par = fec_read_parity(v, rsb, block_offset, &offset, &buf, bio_prio(bio));
 			if (IS_ERR(par))
 				return PTR_ERR(par);
 		}
@@ -210,6 +219,7 @@ static int fec_read_bufs(struct dm_verity *v, struct dm_verity_io *io,
 	u8 *bbuf, *rs_block;
 	u8 want_digest[HASH_MAX_DIGESTSIZE];
 	unsigned int n, k;
+	struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size);
 
 	if (neras)
 		*neras = 0;
@@ -248,7 +258,7 @@ static int fec_read_bufs(struct dm_verity *v, struct dm_verity_io *io,
 			bufio = v->bufio;
 		}
 
-		bbuf = dm_bufio_read(bufio, block, &buf, IOPRIO_DEFAULT);
+		bbuf = dm_bufio_read(bufio, block, &buf, bio_prio(bio));
 		if (IS_ERR(bbuf)) {
 			DMWARN_LIMIT("%s: FEC %llu: read failed (%llu): %ld",
 				     v->data_dev->name,
diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c
index 4758bfe2c156..8cbf81fc0031 100644
--- a/drivers/md/dm-verity-target.c
+++ b/drivers/md/dm-verity-target.c
@@ -51,6 +51,7 @@ static DEFINE_STATIC_KEY_FALSE(use_tasklet_enabled);
 struct dm_verity_prefetch_work {
 	struct work_struct work;
 	struct dm_verity *v;
+	unsigned short ioprio;
 	sector_t block;
 	unsigned int n_blocks;
 };
@@ -294,6 +295,7 @@ static int verity_verify_level(struct dm_verity *v, struct dm_verity_io *io,
 	int r;
 	sector_t hash_block;
 	unsigned int offset;
+	struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size);
 
 	verity_hash_at_level(v, block, level, &hash_block, &offset);
 
@@ -308,7 +310,7 @@ static int verity_verify_level(struct dm_verity *v, struct dm_verity_io *io,
 			return -EAGAIN;
 		}
 	} else
-		data = dm_bufio_read(v->bufio, hash_block, &buf, IOPRIO_DEFAULT);
+		data = dm_bufio_read(v->bufio, hash_block, &buf, bio_prio(bio));
 
 	if (IS_ERR(data))
 		return PTR_ERR(data);
@@ -720,13 +722,14 @@ static void verity_prefetch_io(struct work_struct *work)
 no_prefetch_cluster:
 		dm_bufio_prefetch(v->bufio, hash_block_start,
 				  hash_block_end - hash_block_start + 1,
-				  IOPRIO_DEFAULT);
+				  pw->ioprio);
 	}
 
 	kfree(pw);
 }
 
-static void verity_submit_prefetch(struct dm_verity *v, struct dm_verity_io *io)
+static void verity_submit_prefetch(struct dm_verity *v, struct dm_verity_io *io,
+				   unsigned short ioprio)
 {
 	sector_t block = io->block;
 	unsigned int n_blocks = io->n_blocks;
@@ -754,6 +757,7 @@ static void verity_submit_prefetch(struct dm_verity *v, struct dm_verity_io *io)
 	pw->v = v;
 	pw->block = block;
 	pw->n_blocks = n_blocks;
+	pw->ioprio = ioprio;
 	queue_work(v->verify_wq, &pw->work);
 }
 
@@ -796,7 +800,7 @@ static int verity_map(struct dm_target *ti, struct bio *bio)
 
 	verity_fec_init_io(io);
 
-	verity_submit_prefetch(v, io);
+	verity_submit_prefetch(v, io, bio_prio(bio));
 
 	submit_bio_noacct(bio);
 
-- 
2.34.1