block: Integrity checksum flag

Make the choice of checksum a per-I/O property by introducing a flag
that can be inspected by the SCSI layer. There are several reasons for
this:

 1. It allows us to switch choice of checksum without unloading and
    reloading the HBA driver.

 2. During error recovery we need to be able to tell the HBA that
    checksums read from disk should not be verified and converted to IP
    checksums.

 3. For error injection purposes we need to be able to write a bad guard
    tag to storage. Since the storage device only supports T10 CRC we
    need to be able to disable IP checksum conversion on the HBA.
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

block/bio-integrity.c

@@ -297,6 +297,9 @@ int bio_integrity_prep(struct bio *bio)
 	bip->bip_iter.bi_size = len;
 	bip_set_seed(bip, bio->bi_iter.bi_sector);
 
+	if (bi->flags & BLK_INTEGRITY_IP_CHECKSUM)
+		bip->bip_flags |= BIP_IP_CHECKSUM;
+
 	/* Map it */
 	offset = offset_in_page(buf);
 	for (i = 0 ; i < nr_pages ; i++) {

drivers/scsi/sd_dif.c

@@ -255,12 +255,14 @@ void sd_dif_config_host(struct scsi_disk *sdkp)
 		return;
 
 	/* Enable DMA of protection information */
-	if (scsi_host_get_guard(sdkp->device->host) & SHOST_DIX_GUARD_IP)
+	if (scsi_host_get_guard(sdkp->device->host) & SHOST_DIX_GUARD_IP) {
 		if (type == SD_DIF_TYPE3_PROTECTION)
 			blk_integrity_register(disk, &dif_type3_integrity_ip);
 		else
 			blk_integrity_register(disk, &dif_type1_integrity_ip);
-	else
+
+		disk->integrity->flags |= BLK_INTEGRITY_IP_CHECKSUM;
+	} else
 		if (type == SD_DIF_TYPE3_PROTECTION)
 			blk_integrity_register(disk, &dif_type3_integrity_crc);
 		else

include/linux/bio.h

@@ -328,6 +328,7 @@ enum bip_flags {
 	BIP_MAPPED_INTEGRITY	= 1 << 1, /* ref tag has been remapped */
 	BIP_CTRL_NOCHECK	= 1 << 2, /* disable HBA integrity checking */
 	BIP_DISK_NOCHECK	= 1 << 3, /* disable disk integrity checking */
+	BIP_IP_CHECKSUM		= 1 << 4, /* IP checksum */
 };
 
 static inline sector_t bip_get_seed(struct bio_integrity_payload *bip)

include/linux/blkdev.h

@@ -1462,6 +1462,7 @@ enum blk_integrity_flags {
 	BLK_INTEGRITY_VERIFY		= 1 << 0,
 	BLK_INTEGRITY_GENERATE		= 1 << 1,
 	BLK_INTEGRITY_DEVICE_CAPABLE	= 1 << 2,
+	BLK_INTEGRITY_IP_CHECKSUM	= 1 << 3,
 };
 
 struct blk_integrity_iter {