block: introduce pi_tuple_size field in blk_integrity

Introduce a new pi_tuple_size field in struct blk_integrity to
explicitly represent the size (in bytes) of the protection information
(PI) tuple. This is a prep patch.
Add validation in blk_validate_integrity_limits() to ensure that
pi size matches the expected size for known checksum types and never
exceeds the pi_tuple_size.

Suggested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
Link: https://lore.kernel.org/20250630090548.3317-3-anuj20.g@samsung.com
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: Anuj Gupta

block/blk-settings.c

@@ -14,6 +14,8 @@
 #include <linux/jiffies.h>
 #include <linux/gfp.h>
 #include <linux/dma-mapping.h>
+#include <linux/t10-pi.h>
+#include <linux/crc64.h>
 
 #include "blk.h"
 #include "blk-rq-qos.h"
@@ -135,6 +137,42 @@ static int blk_validate_integrity_limits(struct queue_limits *lim)
 		return -EINVAL;
 	}
 
+	if (bi->pi_tuple_size > bi->metadata_size) {
+		pr_warn("pi_tuple_size (%u) exceeds metadata_size (%u)\n",
+			 bi->pi_tuple_size,
+			 bi->metadata_size);
+		return -EINVAL;
+	}
+
+	switch (bi->csum_type) {
+	case BLK_INTEGRITY_CSUM_NONE:
+		if (bi->pi_tuple_size) {
+			pr_warn("pi_tuple_size must be 0 when checksum type \
+				 is none\n");
+			return -EINVAL;
+		}
+		break;
+	case BLK_INTEGRITY_CSUM_CRC:
+	case BLK_INTEGRITY_CSUM_IP:
+		if (bi->pi_tuple_size != sizeof(struct t10_pi_tuple)) {
+			pr_warn("pi_tuple_size mismatch for T10 PI: expected \
+				 %zu, got %u\n",
+				 sizeof(struct t10_pi_tuple),
+				 bi->pi_tuple_size);
+			return -EINVAL;
+		}
+		break;
+	case BLK_INTEGRITY_CSUM_CRC64:
+		if (bi->pi_tuple_size != sizeof(struct crc64_pi_tuple)) {
+			pr_warn("pi_tuple_size mismatch for CRC64 PI: \
+				 expected %zu, got %u\n",
+				 sizeof(struct crc64_pi_tuple),
+				 bi->pi_tuple_size);
+			return -EINVAL;
+		}
+		break;
+	}
+
 	if (!bi->interval_exp)
 		bi->interval_exp = ilog2(lim->logical_block_size);
 

drivers/nvme/host/core.c

@@ -1867,6 +1867,8 @@ static bool nvme_init_integrity(struct nvme_ns_head *head,
 	}
 
 	bi->metadata_size = head->ms;
+	if (bi->csum_type)
+		bi->pi_tuple_size = head->pi_size;
 	bi->pi_offset = info->pi_offset;
 	return true;
 }

drivers/scsi/sd_dif.c

@@ -53,6 +53,7 @@ void sd_dif_config_host(struct scsi_disk *sdkp, struct queue_limits *lim)
 		bi->flags |= BLK_INTEGRITY_REF_TAG;
 
 	bi->metadata_size = sizeof(struct t10_pi_tuple);
+	bi->pi_tuple_size = bi->metadata_size;
 
 	if (dif && type) {
 		bi->flags |= BLK_INTEGRITY_DEVICE_CAPABLE;

include/linux/blkdev.h

@@ -120,6 +120,7 @@ struct blk_integrity {
 	unsigned char				pi_offset;
 	unsigned char				interval_exp;
 	unsigned char				tag_size;
+	unsigned char				pi_tuple_size;
 };
 
 typedef unsigned int __bitwise blk_mode_t;