[RFC 1/3] block: add integrity offload

[Kanchan Joshi]

Add a 'offload_type' that is populated by the integrity providers
(e.g., drivers) based on the underlying capability/configuration.

- BLK_INTEGRITY_OFFLOAD_NONE: indicates offload capability is absent.
- BLK_INTEGRITY_OFFLOAD_NO_BUF: offload for which integrity buffer is
not needed.
- BLK_INTEGRITY_OFFLOAD_BUF: offload for which integrity buffer is
needed.

Make block layer skip certain processing (checksum generate/verify,
reftag remapping) that is not compatible with the offload.

Users (e.g., filesystems) can send the flag REQ_INTEGRITY_OFFLOAD to
ask for the offload.

Signed-off-by: Kanchan Joshi <joshi.k at samsung.com>
Co-developed-by: Anuj Gupta <anuj20.g at samsung.com>
Signed-off-by: Anuj Gupta <anuj20.g at samsung.com>
---
 block/bio-integrity.c     | 42 ++++++++++++++++++++++++++++++++++++++-
 block/t10-pi.c            |  7 +++++++
 include/linux/blk_types.h |  3 +++
 include/linux/blkdev.h    |  7 +++++++
 4 files changed, 58 insertions(+), 1 deletion(-)

diff --git a/block/bio-integrity.c b/block/bio-integrity.c
index 5d81ad9a3d20..05872b5ad9aa 100644
--- a/block/bio-integrity.c
+++ b/block/bio-integrity.c
@@ -413,6 +413,41 @@ int bio_integrity_map_iter(struct bio *bio, struct uio_meta *meta)
 	return ret;
 }
 
+static bool bio_integrity_offload(struct bio *bio)
+{
+	struct bio_integrity_payload *bip;
+	struct blk_integrity *bi = blk_get_integrity(bio->bi_bdev->bd_disk);
+	unsigned int len;
+	void *buf;
+	gfp_t gfp = GFP_NOIO;
+
+	if (bi->offload_type == BLK_INTEGRITY_OFFLOAD_NO_BUF)
+		return true;
+
+	/* Allocate kernel buffer for protection data */
+	len = bio_integrity_bytes(bi, bio_sectors(bio));
+	buf = kmalloc(len, gfp | __GFP_ZERO);
+	if (unlikely(buf == NULL))
+		goto err_end_io;
+
+	bip = bio_integrity_alloc(bio, gfp, 1);
+	if (IS_ERR(bip)) {
+		kfree(buf);
+		goto err_end_io;
+	}
+
+	bip->bip_flags |= BIP_BLOCK_INTEGRITY;
+	if (bio_integrity_add_page(bio, virt_to_page(buf), len,
+			offset_in_page(buf)) < len)
+		goto err_end_io;
+
+	return true;
+
+err_end_io:
+	bio->bi_status = BLK_STS_RESOURCE;
+	bio_endio(bio);
+	return false;
+}
 /**
  * bio_integrity_prep - Prepare bio for integrity I/O
  * @bio:	bio to prepare
@@ -443,6 +478,10 @@ bool bio_integrity_prep(struct bio *bio)
 	if (bio_integrity(bio))
 		return true;
 
+	if (bio->bi_opf & REQ_INTEGRITY_OFFLOAD &&
+	    bi->offload_type != BLK_INTEGRITY_OFFLOAD_NONE)
+		return  bio_integrity_offload(bio);
+
 	switch (bio_op(bio)) {
 	case REQ_OP_READ:
 		if (bi->flags & BLK_INTEGRITY_NOVERIFY)
@@ -522,7 +561,8 @@ static void bio_integrity_verify_fn(struct work_struct *work)
 		container_of(work, struct bio_integrity_payload, bip_work);
 	struct bio *bio = bip->bip_bio;
 
-	blk_integrity_verify(bio);
+	if (!(bio->bi_opf & REQ_INTEGRITY_OFFLOAD))
+		blk_integrity_verify(bio);
 
 	kfree(bvec_virt(bip->bip_vec));
 	bio_integrity_free(bio);
diff --git a/block/t10-pi.c b/block/t10-pi.c
index 2d05421f0fa5..9eca1ad5d5e6 100644
--- a/block/t10-pi.c
+++ b/block/t10-pi.c
@@ -452,6 +452,9 @@ void blk_integrity_prepare(struct request *rq)
 
 	if (!(bi->flags & BLK_INTEGRITY_REF_TAG))
 		return;
+	if ((rq->cmd_flags & REQ_INTEGRITY_OFFLOAD) &&
+	    (bi->offload_type != BLK_INTEGRITY_OFFLOAD_NONE))
+		return;
 
 	if (bi->csum_type == BLK_INTEGRITY_CSUM_CRC64)
 		ext_pi_type1_prepare(rq);
@@ -466,6 +469,10 @@ void blk_integrity_complete(struct request *rq, unsigned int nr_bytes)
 	if (!(bi->flags & BLK_INTEGRITY_REF_TAG))
 		return;
 
+	if ((rq->cmd_flags & REQ_INTEGRITY_OFFLOAD) &&
+	    (bi->offload_type != BLK_INTEGRITY_OFFLOAD_NONE))
+		return;
+
 	if (bi->csum_type == BLK_INTEGRITY_CSUM_CRC64)
 		ext_pi_type1_complete(rq, nr_bytes);
 	else
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index dce7615c35e7..65615dbc3e2d 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -378,6 +378,7 @@ enum req_flag_bits {
 	__REQ_DRV,		/* for driver use */
 	__REQ_FS_PRIVATE,	/* for file system (submitter) use */
 	__REQ_ATOMIC,		/* for atomic write operations */
+	__REQ_INTEGRITY_OFFLOAD,/* I/O that wants HW integrity offload */
 	/*
 	 * Command specific flags, keep last:
 	 */
@@ -399,6 +400,8 @@ enum req_flag_bits {
 #define REQ_NOMERGE	(__force blk_opf_t)(1ULL << __REQ_NOMERGE)
 #define REQ_IDLE	(__force blk_opf_t)(1ULL << __REQ_IDLE)
 #define REQ_INTEGRITY	(__force blk_opf_t)(1ULL << __REQ_INTEGRITY)
+#define REQ_INTEGRITY_OFFLOAD \
+			(__force blk_opf_t)(1ULL << __REQ_INTEGRITY_OFFLOAD)
 #define REQ_FUA		(__force blk_opf_t)(1ULL << __REQ_FUA)
 #define REQ_PREFLUSH	(__force blk_opf_t)(1ULL << __REQ_PREFLUSH)
 #define REQ_RAHEAD	(__force blk_opf_t)(1ULL << __REQ_RAHEAD)
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 7ac153e4423a..ef061eb4cb73 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -113,6 +113,12 @@ enum blk_integrity_checksum {
 	BLK_INTEGRITY_CSUM_CRC64	= 3,
 } __packed ;
 
+enum blk_integrity_offload {
+	BLK_INTEGRITY_OFFLOAD_NONE	= 0,
+	BLK_INTEGRITY_OFFLOAD_NO_BUF	= 1,
+	BLK_INTEGRITY_OFFLOAD_BUF	= 2,
+} __packed;
+
 struct blk_integrity {
 	unsigned char				flags;
 	enum blk_integrity_checksum		csum_type;
@@ -120,6 +126,7 @@ struct blk_integrity {
 	unsigned char				pi_offset;
 	unsigned char				interval_exp;
 	unsigned char				tag_size;
+	unsigned char				offload_type;
 };
 
 typedef unsigned int __bitwise blk_mode_t;
-- 
2.25.1