[PATCH v4 1/5] block: use integrity interval instead of sector as seed

[Caleb Sander Mateos <csander@purestorage.com>]

bio_integrity_setup_default() and blk_integrity_iterate() set the
integrity seed (initial reference tag) to the absolute address in the
block device in units of 512-byte sectors. However, Type 1 and Type 2
ref tags are actually the least significant bits of the integrity
interval number. On devices with integrity interval size > 512 bytes,
the ref tag seed thus isn't the correct initial ref tag. The ref tag
seed is correctly incremented/decremented in units of integrity
intervals in bio_integrity_map_iter(), bio_integrity_advance(), and
blk_integrity_interval().

For REQ_OP_{WRITE,READ}, blk_integrity_{prepare,complete}() covers up
this ref tag seed discrepancy by adding/subtracting the difference
between the initial integrity interval and ref tag values to/from each
ref tag in the protection information. However, REQ_OP_ZONE_APPEND can
also carry PI but doesn't go through blk_integrity_prepare() because the
final data location on the zoned block device isn't known until the
operation completes. As a result, the REQ_OP_ZONE_APPEND PI ref tags
start from the ref tag seed, which isn't in integrity interval units.
Subsequent reads of the appended blocks will fail to remap the ref tags
from the expected integrity interval numbers to sector numbers.

Additionally, NVMe and many SCSI transports support offloading ref tag
remapping to the device by specifying the expected initial ref tag in
the command. The kernel doesn't currently take advantage of this, always
remapping ref tags in software for reads and writes and setting the
expected initial ref tag to the integrity interval. Setting the ref tag
seed in units of integrity intervals would be a prerequisite to allowing
the kernel to skip the software remapping and pass the ref tag seed as
the expected initial ref tag in the command.

So compute the ref tag seed in units of integrity intervals instead of
sectors to avoid relying on ref tag remapping for the conversion.

Fixes: 0512a75b98f8 ("block: Introduce REQ_OP_ZONE_APPEND")
Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
Reviewed-by: Anuj Gupta <anuj20.g@samsung.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 block/bio-integrity.c | 3 ++-
 block/t10-pi.c        | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/block/bio-integrity.c b/block/bio-integrity.c
index b23e2434d80c..d20f9002c7c9 100644
--- a/block/bio-integrity.c
+++ b/block/bio-integrity.c
@@ -102,12 +102,13 @@ void bio_integrity_free_buf(struct bio_integrity_payload *bip)
 
 void bio_integrity_setup_default(struct bio *bio)
 {
 	struct blk_integrity *bi = blk_get_integrity(bio->bi_bdev->bd_disk);
 	struct bio_integrity_payload *bip = bio_integrity(bio);
+	u64 seed = bio->bi_iter.bi_sector >> (bi->interval_exp - SECTOR_SHIFT);
 
-	bip_set_seed(bip, bio->bi_iter.bi_sector);
+	bip_set_seed(bip, seed);
 
 	if (bi->csum_type) {
 		bip->bip_flags |= BIP_CHECK_GUARD;
 		if (bi->csum_type == BLK_INTEGRITY_CSUM_IP)
 			bip->bip_flags |= BIP_IP_CHECKSUM;
diff --git a/block/t10-pi.c b/block/t10-pi.c
index a19b4e102a83..e58d5eb6cefb 100644
--- a/block/t10-pi.c
+++ b/block/t10-pi.c
@@ -308,18 +308,19 @@ static blk_status_t blk_integrity_iterate(struct bio *bio,
 					  struct bvec_iter *data_iter,
 					  bool verify)
 {
 	struct blk_integrity *bi = blk_get_integrity(bio->bi_bdev->bd_disk);
 	struct bio_integrity_payload *bip = bio_integrity(bio);
+	u64 seed = data_iter->bi_sector >> (bi->interval_exp - SECTOR_SHIFT);
 	struct blk_integrity_iter iter = {
 		.bio = bio,
 		.bip = bip,
 		.bi = bi,
 		.data_iter = *data_iter,
 		.prot_iter = bip->bip_iter,
 		.interval_remaining = 1 << bi->interval_exp,
-		.seed = data_iter->bi_sector,
+		.seed = seed,
 		.csum = 0,
 	};
 	blk_status_t ret = BLK_STS_OK;
 
 	while (iter.data_iter.bi_size && ret == BLK_STS_OK) {
-- 
2.54.0