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Avoid software ref tag remapping for NVMe devices #1014

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fa2a1f3
blk-integrity: add BLK_EXPECTED_REF_TAG_CAPABLE
calebsander Jun 27, 2026
c4dce78
nvme/core: advertise BLK_EXPECTED_REF_TAG_CAPABLE
calebsander Jun 27, 2026
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18 changes: 18 additions & 0 deletions block/blk-integrity.c
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Original file line number Diff line number Diff line change
Expand Up @@ -141,6 +141,8 @@ bool blk_integrity_merge_rq(struct request_queue *q, struct request *req,
struct request *next)
{
struct bio_integrity_payload *bip, *bip_next;
struct blk_integrity *bi;
u64 intervals;

if (blk_integrity_rq(req) == 0 && blk_integrity_rq(next) == 0)
return true;
Expand All @@ -157,6 +159,13 @@ bool blk_integrity_merge_rq(struct request_queue *q, struct request *req,
bip->app_tag != bip_next->app_tag)
return false;

bi = blk_get_integrity(req->bio->bi_bdev->bd_disk);
intervals = blk_rq_bytes(req) >> bi->interval_exp;
if (bip->bip_flags & BIP_CHECK_REFTAG &&
bi->flags & BLK_EXPECTED_REF_TAG_CAPABLE &&
bip->bip_iter.bi_sector + intervals != bip_next->bip_iter.bi_sector)
return false;

if (req->nr_integrity_segments + next->nr_integrity_segments >
q->limits.max_integrity_segments)
return false;
Expand All @@ -171,7 +180,9 @@ bool blk_integrity_merge_bio(struct request_queue *q, struct request *req,
struct bio *bio)
{
struct bio_integrity_payload *bip, *bip_bio = bio_integrity(bio);
struct blk_integrity *bi;
int nr_integrity_segs;
u64 intervals;

if (blk_integrity_rq(req) == 0 && bip_bio == NULL)
return true;
Expand All @@ -187,6 +198,13 @@ bool blk_integrity_merge_bio(struct request_queue *q, struct request *req,
bip->app_tag != bip_bio->app_tag)
return false;

bi = blk_get_integrity(req->bio->bi_bdev->bd_disk);
intervals = blk_rq_bytes(req) >> bi->interval_exp;
if (bip->bip_flags & BIP_CHECK_REFTAG &&
bi->flags & BLK_EXPECTED_REF_TAG_CAPABLE &&
bip->bip_iter.bi_sector + intervals != bip_bio->bip_iter.bi_sector)
return false;

nr_integrity_segs = blk_rq_count_integrity_sg(q, bio);
if (req->nr_integrity_segments + nr_integrity_segs >
q->limits.max_integrity_segments)
Expand Down
3 changes: 2 additions & 1 deletion block/t10-pi.c
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Original file line number Diff line number Diff line change
Expand Up @@ -546,7 +546,8 @@ static void blk_integrity_remap(struct request *rq, unsigned int nr_bytes,
unsigned intervals = nr_bytes >> bi->interval_exp;
struct bio *bio;

if (!(bi->flags & BLK_INTEGRITY_REF_TAG))
if (!(bi->flags & BLK_INTEGRITY_REF_TAG) ||
bi->flags & BLK_EXPECTED_REF_TAG_CAPABLE)
return;

__rq_for_each_bio(bio, rq) {
Expand Down
20 changes: 10 additions & 10 deletions drivers/nvme/host/core.c
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Original file line number Diff line number Diff line change
Expand Up @@ -916,8 +916,7 @@ static void nvme_set_app_tag(struct request *req, struct nvme_command *cmnd)
static void nvme_set_ref_tag(struct nvme_ns *ns, struct nvme_command *cmnd,
struct request *req)
{
u32 upper, lower;
u64 ref48;
u64 ref_tag;

/* only type1 and type 2 PI formats have a reftag */
switch (ns->head->pi_type) {
Expand All @@ -928,18 +927,19 @@ static void nvme_set_ref_tag(struct nvme_ns *ns, struct nvme_command *cmnd,
return;
}

ref_tag = full_pi_ref_tag(req);
if (blk_integrity_rq(req))
ref_tag = bio_integrity(req->bio)->bip_iter.bi_sector;

/* both rw and write zeroes share the same reftag format */
switch (ns->head->guard_type) {
case NVME_NVM_NS_16B_GUARD:
cmnd->rw.reftag = cpu_to_le32(t10_pi_ref_tag(req));
cmnd->rw.reftag = cpu_to_le32(lower_32_bits(ref_tag));
break;
case NVME_NVM_NS_64B_GUARD:
ref48 = ext_pi_ref_tag(req);
lower = lower_32_bits(ref48);
upper = upper_32_bits(ref48);

cmnd->rw.reftag = cpu_to_le32(lower);
cmnd->rw.cdw3 = cpu_to_le32(upper);
ref_tag = lower_48_bits(ref_tag);
cmnd->rw.reftag = cpu_to_le32(lower_32_bits(ref_tag));
cmnd->rw.cdw3 = cpu_to_le32(upper_32_bits(ref_tag));
break;
default:
break;
Expand Down Expand Up @@ -1891,7 +1891,7 @@ static bool nvme_init_integrity(struct nvme_ns_head *head,
break;
}

bi->flags |= BLK_SPLIT_INTERVAL_CAPABLE;
bi->flags |= BLK_SPLIT_INTERVAL_CAPABLE | BLK_EXPECTED_REF_TAG_CAPABLE;
bi->metadata_size = head->ms;
if (bi->csum_type) {
bi->pi_tuple_size = head->pi_size;
Expand Down
2 changes: 2 additions & 0 deletions include/linux/blk-integrity.h
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,8 @@ enum blk_integrity_flags {
BLK_INTEGRITY_REF_TAG = 1 << 3,
BLK_INTEGRITY_STACKED = 1 << 4,
BLK_SPLIT_INTERVAL_CAPABLE = 1 << 5,
/* Device I/O specifies expected initial ref tag independent of LBA */
BLK_EXPECTED_REF_TAG_CAPABLE = 1 << 6,
};

const char *blk_integrity_profile_name(struct blk_integrity *bi);
Expand Down
5 changes: 0 additions & 5 deletions include/linux/t10-pi.h
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Original file line number Diff line number Diff line change
Expand Up @@ -68,9 +68,4 @@ static inline u64 lower_48_bits(u64 n)
return n & ((1ull << 48) - 1);
}

static inline u64 ext_pi_ref_tag(struct request *rq)
{
return lower_48_bits(full_pi_ref_tag(rq));
}

#endif