// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * SCSI Block Commands (SBC) parsing and emulation.
 *
 * (c) Copyright 2002-2013 Datera, Inc.
 *
 * Nicholas A. Bellinger <nab@kernel.org>
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/ratelimit.h>
#include <linux/crc-t10dif.h>
#include <linux/t10-pi.h>
#include <asm/unaligned.h>
#include <scsi/scsi_proto.h>
#include <scsi/scsi_tcq.h>

#include <target/target_core_base.h>
#include <target/target_core_backend.h>
#include <target/target_core_fabric.h>

#include "target_core_internal.h"
#include "target_core_ua.h"
#include "target_core_alua.h"

static sense_reason_t
sbc_check_prot(struct se_device *, struct se_cmd *, unsigned char *, u32, bool);
static sense_reason_t sbc_execute_unmap(struct se_cmd *cmd);

static sense_reason_t
sbc_emulate_readcapacity(struct se_cmd *cmd)
{
        struct se_device *dev = cmd->se_dev;
        unsigned char *cdb = cmd->t_task_cdb;
        unsigned long long blocks_long = dev->transport->get_blocks(dev);
        unsigned char *rbuf;
        unsigned char buf[8];
        u32 blocks;

        /*
         * SBC-2 says:
         *   If the PMI bit is set to zero and the LOGICAL BLOCK
         *   ADDRESS field is not set to zero, the device server shall
         *   terminate the command with CHECK CONDITION status with
         *   the sense key set to ILLEGAL REQUEST and the additional
         *   sense code set to INVALID FIELD IN CDB.
         *
         * In SBC-3, these fields are obsolete, but some SCSI
         * compliance tests actually check this, so we might as well
         * follow SBC-2.
         */
        if (!(cdb[8] & 1) && !!(cdb[2] | cdb[3] | cdb[4] | cdb[5]))
                return TCM_INVALID_CDB_FIELD;

        if (blocks_long >= 0x00000000ffffffff)
                blocks = 0xffffffff;
        else
                blocks = (u32)blocks_long;

        put_unaligned_be32(blocks, &buf[0]);
        put_unaligned_be32(dev->dev_attrib.block_size, &buf[4]);

        rbuf = transport_kmap_data_sg(cmd);
        if (rbuf) {
                memcpy(rbuf, buf, min_t(u32, sizeof(buf), cmd->data_length));
                transport_kunmap_data_sg(cmd);
        }

        target_complete_cmd_with_length(cmd, GOOD, 8);
        return 0;
}

static sense_reason_t
sbc_emulate_readcapacity_16(struct se_cmd *cmd)
{
        struct se_device *dev = cmd->se_dev;
        struct se_session *sess = cmd->se_sess;
        int pi_prot_type = dev->dev_attrib.pi_prot_type;

        unsigned char *rbuf;
        unsigned char buf[32];
        unsigned long long blocks = dev->transport->get_blocks(dev);

        memset(buf, 0, sizeof(buf));
        put_unaligned_be64(blocks, &buf[0]);
        put_unaligned_be32(dev->dev_attrib.block_size, &buf[8]);
        /*
         * Set P_TYPE and PROT_EN bits for DIF support
         */
        if (sess->sup_prot_ops & (TARGET_PROT_DIN_PASS | TARGET_PROT_DOUT_PASS)) {
                /*
                 * Only override a device's pi_prot_type if no T10-PI is
                 * available, and sess_prot_type has been explicitly enabled.
                 */
                if (!pi_prot_type)
                        pi_prot_type = sess->sess_prot_type;

                if (pi_prot_type)
                        buf[12] = (pi_prot_type - 1) << 1 | 0x1;
        }

        if (dev->transport->get_lbppbe)
                buf[13] = dev->transport->get_lbppbe(dev) & 0x0f;

        if (dev->transport->get_alignment_offset_lbas) {
                u16 lalba = dev->transport->get_alignment_offset_lbas(dev);

                put_unaligned_be16(lalba, &buf[14]);
        }

        /*
         * Set Thin Provisioning Enable bit following sbc3r22 in section
         * READ CAPACITY (16) byte 14 if emulate_tpu or emulate_tpws is enabled.
         */
        if (dev->dev_attrib.emulate_tpu || dev->dev_attrib.emulate_tpws) {
                buf[14] |= 0x80;

                /*
                 * LBPRZ signifies that zeroes will be read back from an LBA after
                 * an UNMAP or WRITE SAME w/ unmap bit (sbc3r36 5.16.2)
                 */
                if (dev->dev_attrib.unmap_zeroes_data)
                        buf[14] |= 0x40;
        }

        rbuf = transport_kmap_data_sg(cmd);
        if (rbuf) {
                memcpy(rbuf, buf, min_t(u32, sizeof(buf), cmd->data_length));
                transport_kunmap_data_sg(cmd);
        }

        target_complete_cmd_with_length(cmd, GOOD, 32);
        return 0;
}

static sense_reason_t
sbc_emulate_startstop(struct se_cmd *cmd)
{
        unsigned char *cdb = cmd->t_task_cdb;

        /*
         * See sbc3r36 section 5.25
         * Immediate bit should be set since there is nothing to complete
         * POWER CONDITION MODIFIER 0h
         */
        if (!(cdb[1] & 1) || cdb[2] || cdb[3])
                return TCM_INVALID_CDB_FIELD;

        /*
         * See sbc3r36 section 5.25
         * POWER CONDITION 0h START_VALID - process START and LOEJ
         */
        if (cdb[4] >> 4 & 0xf)
                return TCM_INVALID_CDB_FIELD;

        /*
         * See sbc3r36 section 5.25
         * LOEJ 0h - nothing to load or unload
         * START 1h - we are ready
         */
        if (!(cdb[4] & 1) || (cdb[4] & 2) || (cdb[4] & 4))
                return TCM_INVALID_CDB_FIELD;

        target_complete_cmd(cmd, SAM_STAT_GOOD);
        return 0;
}

sector_t sbc_get_write_same_sectors(struct se_cmd *cmd)
{
        u32 num_blocks;

        if (cmd->t_task_cdb[0] == WRITE_SAME)
                num_blocks = get_unaligned_be16(&cmd->t_task_cdb[7]);
        else if (cmd->t_task_cdb[0] == WRITE_SAME_16)
                num_blocks = get_unaligned_be32(&cmd->t_task_cdb[10]);
        else /* WRITE_SAME_32 via VARIABLE_LENGTH_CMD */
                num_blocks = get_unaligned_be32(&cmd->t_task_cdb[28]);

        /*
         * Use the explicit range when non zero is supplied, otherwise calculate
         * the remaining range based on ->get_blocks() - starting LBA.
         */
        if (num_blocks)
                return num_blocks;

        return cmd->se_dev->transport->get_blocks(cmd->se_dev) -
                cmd->t_task_lba + 1;
}
EXPORT_SYMBOL(sbc_get_write_same_sectors);

static sense_reason_t
sbc_execute_write_same_unmap(struct se_cmd *cmd)
{
        struct sbc_ops *ops = cmd->protocol_data;
        sector_t nolb = sbc_get_write_same_sectors(cmd);
        sense_reason_t ret;

        if (nolb) {
                ret = ops->execute_unmap(cmd, cmd->t_task_lba, nolb);
                if (ret)
                        return ret;
        }

        target_complete_cmd(cmd, GOOD);
        return 0;
}

static sense_reason_t
sbc_emulate_noop(struct se_cmd *cmd)
{
        target_complete_cmd(cmd, GOOD);
        return 0;
}

static inline u32 sbc_get_size(struct se_cmd *cmd, u32 sectors)
{
        return cmd->se_dev->dev_attrib.block_size * sectors;
}

static inline u32 transport_get_sectors_6(unsigned char *cdb)
{
        /*
         * Use 8-bit sector value.  SBC-3 says:
         *
         *   A TRANSFER LENGTH field set to zero specifies that 256
         *   logical blocks shall be written.  Any other value
         *   specifies the number of logical blocks that shall be
         *   written.
         */
        return cdb[4] ? : 256;
}

static inline u32 transport_get_sectors_10(unsigned char *cdb)
{
        return get_unaligned_be16(&cdb[7]);
}

static inline u32 transport_get_sectors_12(unsigned char *cdb)
{
        return get_unaligned_be32(&cdb[6]);
}

static inline u32 transport_get_sectors_16(unsigned char *cdb)
{
        return get_unaligned_be32(&cdb[10]);
}

/*
 * Used for VARIABLE_LENGTH_CDB WRITE_32 and READ_32 variants
 */
static inline u32 transport_get_sectors_32(unsigned char *cdb)
{
        return get_unaligned_be32(&cdb[28]);

}

static inline u32 transport_lba_21(unsigned char *cdb)
{
        return get_unaligned_be24(&cdb[1]) & 0x1fffff;
}

static inline u32 transport_lba_32(unsigned char *cdb)
{
        return get_unaligned_be32(&cdb[2]);
}

static inline unsigned long long transport_lba_64(unsigned char *cdb)
{
        return get_unaligned_be64(&cdb[2]);
}

/*
 * For VARIABLE_LENGTH_CDB w/ 32 byte extended CDBs
 */
static inline unsigned long long transport_lba_64_ext(unsigned char *cdb)
{
        return get_unaligned_be64(&cdb[12]);
}

static sense_reason_t
sbc_setup_write_same(struct se_cmd *cmd, unsigned char *flags, struct sbc_ops *ops)
{
        struct se_device *dev = cmd->se_dev;
        sector_t end_lba = dev->transport->get_blocks(dev) + 1;
        unsigned int sectors = sbc_get_write_same_sectors(cmd);
        sense_reason_t ret;

        if ((flags[0] & 0x04) || (flags[0] & 0x02)) {
                pr_err("WRITE_SAME PBDATA and LBDATA"
                        " bits not supported for Block Discard"
                        " Emulation\n");
                return TCM_UNSUPPORTED_SCSI_OPCODE;
        }
        if (sectors > cmd->se_dev->dev_attrib.max_write_same_len) {
                pr_warn("WRITE_SAME sectors: %u exceeds max_write_same_len: %u\n",
                        sectors, cmd->se_dev->dev_attrib.max_write_same_len);
                return TCM_INVALID_CDB_FIELD;
        }
        /*
         * Sanity check for LBA wrap and request past end of device.
         */
        if (((cmd->t_task_lba + sectors) < cmd->t_task_lba) ||
            ((cmd->t_task_lba + sectors) > end_lba)) {
                pr_err("WRITE_SAME exceeds last lba %llu (lba %llu, sectors %u)\n",
                       (unsigned long long)end_lba, cmd->t_task_lba, sectors);
                return TCM_ADDRESS_OUT_OF_RANGE;
        }

        /* We always have ANC_SUP == 0 so setting ANCHOR is always an error */
        if (flags[0] & 0x10) {
                pr_warn("WRITE SAME with ANCHOR not supported\n");
                return TCM_INVALID_CDB_FIELD;
        }
        /*
         * Special case for WRITE_SAME w/ UNMAP=1 that ends up getting
         * translated into block discard requests within backend code.
         */
        if (flags[0] & 0x08) {
                if (!ops->execute_unmap)
                        return TCM_UNSUPPORTED_SCSI_OPCODE;

                if (!dev->dev_attrib.emulate_tpws) {
                        pr_err("Got WRITE_SAME w/ UNMAP=1, but backend device"
                               " has emulate_tpws disabled\n");
                        return TCM_UNSUPPORTED_SCSI_OPCODE;
                }
                cmd->execute_cmd = sbc_execute_write_same_unmap;
                return 0;
        }
        if (!ops->execute_write_same)
                return TCM_UNSUPPORTED_SCSI_OPCODE;

        ret = sbc_check_prot(dev, cmd, &cmd->t_task_cdb[0], sectors, true);
        if (ret)
                return ret;

        cmd->execute_cmd = ops->execute_write_same;
        return 0;
}

static sense_reason_t xdreadwrite_callback(struct se_cmd *cmd, bool success,
                                           int *post_ret)
{
        unsigned char *buf, *addr;
        struct scatterlist *sg;
        unsigned int offset;
        sense_reason_t ret = TCM_NO_SENSE;
        int i, count;

        if (!success)
                return 0;

        /*
         * From sbc3r22.pdf section 5.48 XDWRITEREAD (10) command
         *
         * 1) read the specified logical block(s);
         * 2) transfer logical blocks from the data-out buffer;
         * 3) XOR the logical blocks transferred from the data-out buffer with
         *    the logical blocks read, storing the resulting XOR data in a buffer;
         * 4) if the DISABLE WRITE bit is set to zero, then write the logical
         *    blocks transferred from the data-out buffer; and
         * 5) transfer the resulting XOR data to the data-in buffer.
         */
        buf = kmalloc(cmd->data_length, GFP_KERNEL);
        if (!buf) {
                pr_err("Unable to allocate xor_callback buf\n");
                return TCM_OUT_OF_RESOURCES;
        }
        /*
         * Copy the scatterlist WRITE buffer located at cmd->t_data_sg
         * into the locally allocated *buf
         */
        sg_copy_to_buffer(cmd->t_data_sg,
                          cmd->t_data_nents,
                          buf,
                          cmd->data_length);

        /*
         * Now perform the XOR against the BIDI read memory located at
         * cmd->t_mem_bidi_list
         */

        offset = 0;
        for_each_sg(cmd->t_bidi_data_sg, sg, cmd->t_bidi_data_nents, count) {
                addr = kmap_atomic(sg_page(sg));
                if (!addr) {
                        ret = TCM_OUT_OF_RESOURCES;
                        goto out;
                }

                for (i = 0; i < sg->length; i++)
                        *(addr + sg->offset + i) ^= *(buf + offset + i);

                offset += sg->length;
                kunmap_atomic(addr);
        }

out:
        kfree(buf);
        return ret;
}

static sense_reason_t
sbc_execute_rw(struct se_cmd *cmd)
{
        struct sbc_ops *ops = cmd->protocol_data;

        return ops->execute_rw(cmd, cmd->t_data_sg, cmd->t_data_nents,
                               cmd->data_direction);
}

static sense_reason_t compare_and_write_post(struct se_cmd *cmd, bool success,
                                             int *post_ret)
{
        struct se_device *dev = cmd->se_dev;
        sense_reason_t ret = TCM_NO_SENSE;

        spin_lock_irq(&cmd->t_state_lock);
        if (success) {
                *post_ret = 1;

                if (cmd->scsi_status == SAM_STAT_CHECK_CONDITION)
                        ret = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
        }
        spin_unlock_irq(&cmd->t_state_lock);

        /*
         * Unlock ->caw_sem originally obtained during sbc_compare_and_write()
         * before the original READ I/O submission.
         */
        up(&dev->caw_sem);

        return ret;
}

static sense_reason_t compare_and_write_callback(struct se_cmd *cmd, bool success,
                                                 int *post_ret)
{
        struct se_device *dev = cmd->se_dev;
        struct sg_table write_tbl = { };
        struct scatterlist *write_sg, *sg;
        unsigned char *buf = NULL, *addr;
        struct sg_mapping_iter m;
        unsigned int offset = 0, len;
        unsigned int nlbas = cmd->t_task_nolb;
        unsigned int block_size = dev->dev_attrib.block_size;
        unsigned int compare_len = (nlbas * block_size);
        sense_reason_t ret = TCM_NO_SENSE;
        int rc, i;

        /*
         * Handle early failure in transport_generic_request_failure(),
         * which will not have taken ->caw_sem yet..
         */
        if (!success && (!cmd->t_data_sg || !cmd->t_bidi_data_sg))
                return TCM_NO_SENSE;
        /*
         * Handle special case for zero-length COMPARE_AND_WRITE
         */
        if (!cmd->data_length)
                goto out;
        /*
         * Immediately exit + release dev->caw_sem if command has already
         * been failed with a non-zero SCSI status.
         */
        if (cmd->scsi_status) {
                pr_debug("compare_and_write_callback: non zero scsi_status:"
                        " 0x%02x\n", cmd->scsi_status);
                *post_ret = 1;
                if (cmd->scsi_status == SAM_STAT_CHECK_CONDITION)
                        ret = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
                goto out;
        }

        buf = kzalloc(cmd->data_length, GFP_KERNEL);
        if (!buf) {
                pr_err("Unable to allocate compare_and_write buf\n");
                ret = TCM_OUT_OF_RESOURCES;
                goto out;
        }

        if (sg_alloc_table(&write_tbl, cmd->t_data_nents, GFP_KERNEL) < 0) {
                pr_err("Unable to allocate compare_and_write sg\n");
                ret = TCM_OUT_OF_RESOURCES;
                goto out;
        }
        write_sg = write_tbl.sgl;
        /*
         * Setup verify and write data payloads from total NumberLBAs.
         */
        rc = sg_copy_to_buffer(cmd->t_data_sg, cmd->t_data_nents, buf,
                               cmd->data_length);
        if (!rc) {
                pr_err("sg_copy_to_buffer() failed for compare_and_write\n");
                ret = TCM_OUT_OF_RESOURCES;
                goto out;
        }
        /*
         * Compare against SCSI READ payload against verify payload
         */
        for_each_sg(cmd->t_bidi_data_sg, sg, cmd->t_bidi_data_nents, i) {
                addr = (unsigned char *)kmap_atomic(sg_page(sg));
                if (!addr) {
                        ret = TCM_OUT_OF_RESOURCES;
                        goto out;
                }

                len = min(sg->length, compare_len);

                if (memcmp(addr, buf + offset, len)) {
                        pr_warn("Detected MISCOMPARE for addr: %p buf: %p\n",
                                addr, buf + offset);
                        kunmap_atomic(addr);
                        goto miscompare;
                }
                kunmap_atomic(addr);

                offset += len;
                compare_len -= len;
                if (!compare_len)
                        break;
        }

        i = 0;
        len = cmd->t_task_nolb * block_size;
        sg_miter_start(&m, cmd->t_data_sg, cmd->t_data_nents, SG_MITER_TO_SG);
        /*
         * Currently assumes NoLB=1 and SGLs are PAGE_SIZE..
         */
        while (len) {
                sg_miter_next(&m);

                if (block_size < PAGE_SIZE) {
                        sg_set_page(&write_sg[i], m.page, block_size,
                                    m.piter.sg->offset + block_size);
                } else {
                        sg_miter_next(&m);
                        sg_set_page(&write_sg[i], m.page, block_size,
                                    m.piter.sg->offset);
                }
                len -= block_size;
                i++;
        }
        sg_miter_stop(&m);
        /*
         * Save the original SGL + nents values before updating to new
         * assignments, to be released in transport_free_pages() ->
         * transport_reset_sgl_orig()
         */
        cmd->t_data_sg_orig = cmd->t_data_sg;
        cmd->t_data_sg = write_sg;
        cmd->t_data_nents_orig = cmd->t_data_nents;
        cmd->t_data_nents = 1;

        cmd->sam_task_attr = TCM_HEAD_TAG;
        cmd->transport_complete_callback = compare_and_write_post;
        /*
         * Now reset ->execute_cmd() to the normal sbc_execute_rw() handler
         * for submitting the adjusted SGL to write instance user-data.
         */
        cmd->execute_cmd = sbc_execute_rw;

        spin_lock_irq(&cmd->t_state_lock);
        cmd->t_state = TRANSPORT_PROCESSING;
        cmd->transport_state |= CMD_T_ACTIVE | CMD_T_SENT;
        spin_unlock_irq(&cmd->t_state_lock);

        __target_execute_cmd(cmd, false);

        kfree(buf);
        return ret;

miscompare:
        pr_warn("Target/%s: Send MISCOMPARE check condition and sense\n",
                dev->transport->name);
        ret = TCM_MISCOMPARE_VERIFY;
out:
        /*
         * In the MISCOMPARE or failure case, unlock ->caw_sem obtained in
         * sbc_compare_and_write() before the original READ I/O submission.
         */
        up(&dev->caw_sem);
        sg_free_table(&write_tbl);
        kfree(buf);
        return ret;
}

static sense_reason_t
sbc_compare_and_write(struct se_cmd *cmd)
{
        struct sbc_ops *ops = cmd->protocol_data;
        struct se_device *dev = cmd->se_dev;
        sense_reason_t ret;
        int rc;
        /*
         * Submit the READ first for COMPARE_AND_WRITE to perform the
         * comparision using SGLs at cmd->t_bidi_data_sg..
         */
        rc = down_interruptible(&dev->caw_sem);
        if (rc != 0) {
                cmd->transport_complete_callback = NULL;
                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
        }
        /*
         * Reset cmd->data_length to individual block_size in order to not
         * confuse backend drivers that depend on this value matching the
         * size of the I/O being submitted.
         */
        cmd->data_length = cmd->t_task_nolb * dev->dev_attrib.block_size;

        ret = ops->execute_rw(cmd, cmd->t_bidi_data_sg, cmd->t_bidi_data_nents,
                              DMA_FROM_DEVICE);
        if (ret) {
                cmd->transport_complete_callback = NULL;
                up(&dev->caw_sem);
                return ret;
        }
        /*
         * Unlock of dev->caw_sem to occur in compare_and_write_callback()
         * upon MISCOMPARE, or in compare_and_write_done() upon completion
         * of WRITE instance user-data.
         */
        return TCM_NO_SENSE;
}

static int
sbc_set_prot_op_checks(u8 protect, bool fabric_prot, enum target_prot_type prot_type,
                       bool is_write, struct se_cmd *cmd)
{
        if (is_write) {
                cmd->prot_op = fabric_prot ? TARGET_PROT_DOUT_STRIP :
                               protect ? TARGET_PROT_DOUT_PASS :
                               TARGET_PROT_DOUT_INSERT;
                switch (protect) {
                case 0x0:
                case 0x3:
                        cmd->prot_checks = 0;
                        break;
                case 0x1:
                case 0x5:
                        cmd->prot_checks = TARGET_DIF_CHECK_GUARD;
                        if (prot_type == TARGET_DIF_TYPE1_PROT)
                                cmd->prot_checks |= TARGET_DIF_CHECK_REFTAG;
                        break;
                case 0x2:
                        if (prot_type == TARGET_DIF_TYPE1_PROT)
                                cmd->prot_checks = TARGET_DIF_CHECK_REFTAG;
                        break;
                case 0x4:
                        cmd->prot_checks = TARGET_DIF_CHECK_GUARD;
                        break;
                default:
                        pr_err("Unsupported protect field %d\n", protect);
                        return -EINVAL;
                }
        } else {
                cmd->prot_op = fabric_prot ? TARGET_PROT_DIN_INSERT :
                               protect ? TARGET_PROT_DIN_PASS :
                               TARGET_PROT_DIN_STRIP;
                switch (protect) {
                case 0x0:
                case 0x1:
                case 0x5:
                        cmd->prot_checks = TARGET_DIF_CHECK_GUARD;
                        if (prot_type == TARGET_DIF_TYPE1_PROT)
                                cmd->prot_checks |= TARGET_DIF_CHECK_REFTAG;
                        break;
                case 0x2:
                        if (prot_type == TARGET_DIF_TYPE1_PROT)
                                cmd->prot_checks = TARGET_DIF_CHECK_REFTAG;
                        break;
                case 0x3:
                        cmd->prot_checks = 0;
                        break;
                case 0x4:
                        cmd->prot_checks = TARGET_DIF_CHECK_GUARD;
                        break;
                default:
                        pr_err("Unsupported protect field %d\n", protect);
                        return -EINVAL;
                }
        }

        return 0;
}

static sense_reason_t
sbc_check_prot(struct se_device *dev, struct se_cmd *cmd, unsigned char *cdb,
               u32 sectors, bool is_write)
{
        u8 protect = cdb[1] >> 5;
        int sp_ops = cmd->se_sess->sup_prot_ops;
        int pi_prot_type = dev->dev_attrib.pi_prot_type;
        bool fabric_prot = false;

        if (!cmd->t_prot_sg || !cmd->t_prot_nents) {
                if (unlikely(protect &&
                    !dev->dev_attrib.pi_prot_type && !cmd->se_sess->sess_prot_type)) {
                        pr_err("CDB contains protect bit, but device + fabric does"
                               " not advertise PROTECT=1 feature bit\n");
                        return TCM_INVALID_CDB_FIELD;
                }
                if (cmd->prot_pto)
                        return TCM_NO_SENSE;
        }

        switch (dev->dev_attrib.pi_prot_type) {
        case TARGET_DIF_TYPE3_PROT:
                cmd->reftag_seed = 0xffffffff;
                break;
        case TARGET_DIF_TYPE2_PROT:
                if (protect)
                        return TCM_INVALID_CDB_FIELD;

                cmd->reftag_seed = cmd->t_task_lba;
                break;
        case TARGET_DIF_TYPE1_PROT:
                cmd->reftag_seed = cmd->t_task_lba;
                break;
        case TARGET_DIF_TYPE0_PROT:
                /*
                 * See if the fabric supports T10-PI, and the session has been
                 * configured to allow export PROTECT=1 feature bit with backend
                 * devices that don't support T10-PI.
                 */
                fabric_prot = is_write ?
                              !!(sp_ops & (TARGET_PROT_DOUT_PASS | TARGET_PROT_DOUT_STRIP)) :
                              !!(sp_ops & (TARGET_PROT_DIN_PASS | TARGET_PROT_DIN_INSERT));

                if (fabric_prot && cmd->se_sess->sess_prot_type) {
                        pi_prot_type = cmd->se_sess->sess_prot_type;
                        break;
                }
                if (!protect)
                        return TCM_NO_SENSE;
                /* Fallthrough */
        default:
                pr_err("Unable to determine pi_prot_type for CDB: 0x%02x "
                       "PROTECT: 0x%02x\n", cdb[0], protect);
                return TCM_INVALID_CDB_FIELD;
        }

        if (sbc_set_prot_op_checks(protect, fabric_prot, pi_prot_type, is_write, cmd))
                return TCM_INVALID_CDB_FIELD;

        cmd->prot_type = pi_prot_type;
        cmd->prot_length = dev->prot_length * sectors;

        /**
         * In case protection information exists over the wire
         * we modify command data length to describe pure data.
         * The actual transfer length is data length + protection
         * length
         **/
        if (protect)
                cmd->data_length = sectors * dev->dev_attrib.block_size;

        pr_debug("%s: prot_type=%d, data_length=%d, prot_length=%d "
                 "prot_op=%d prot_checks=%d\n",
                 __func__, cmd->prot_type, cmd->data_length, cmd->prot_length,
                 cmd->prot_op, cmd->prot_checks);

        return TCM_NO_SENSE;
}

static int
sbc_check_dpofua(struct se_device *dev, struct se_cmd *cmd, unsigned char *cdb)
{
        if (cdb[1] & 0x10) {
                /* see explanation in spc_emulate_modesense */
                if (!target_check_fua(dev)) {
                        pr_err("Got CDB: 0x%02x with DPO bit set, but device"
                               " does not advertise support for DPO\n", cdb[0]);
                        return -EINVAL;
                }
        }
        if (cdb[1] & 0x8) {
                if (!target_check_fua(dev)) {
                        pr_err("Got CDB: 0x%02x with FUA bit set, but device"
                               " does not advertise support for FUA write\n",
                               cdb[0]);
                        return -EINVAL;
                }
                cmd->se_cmd_flags |= SCF_FUA;
        }
        return 0;
}

sense_reason_t
sbc_parse_cdb(struct se_cmd *cmd, struct sbc_ops *ops)
{
        struct se_device *dev = cmd->se_dev;
        unsigned char *cdb = cmd->t_task_cdb;
        unsigned int size;
        u32 sectors = 0;
        sense_reason_t ret;

        cmd->protocol_data = ops;

        switch (cdb[0]) {
        case READ_6:
                sectors = transport_get_sectors_6(cdb);
                cmd->t_task_lba = transport_lba_21(cdb);
                cmd->se_cmd_flags |= SCF_SCSI_DATA_CDB;
                cmd->execute_cmd = sbc_execute_rw;
                break;
        case READ_10:
                sectors = transport_get_sectors_10(cdb);
                cmd->t_task_lba = transport_lba_32(cdb);

                if (sbc_check_dpofua(dev, cmd, cdb))
                        return TCM_INVALID_CDB_FIELD;

                ret = sbc_check_prot(dev, cmd, cdb, sectors, false);
                if (ret)
                        return ret;

                cmd->se_cmd_flags |= SCF_SCSI_DATA_CDB;
                cmd->execute_cmd = sbc_execute_rw;
                break;
        case READ_12:
                sectors = transport_get_sectors_12(cdb);
                cmd->t_task_lba = transport_lba_32(cdb);

                if (sbc_check_dpofua(dev, cmd, cdb))
                        return TCM_INVALID_CDB_FIELD;

                ret = sbc_check_prot(dev, cmd, cdb, sectors, false);
                if (ret)
                        return ret;

                cmd->se_cmd_flags |= SCF_SCSI_DATA_CDB;
                cmd->execute_cmd = sbc_execute_rw;
                break;
        case READ_16:
                sectors = transport_get_sectors_16(cdb);
                cmd->t_task_lba = transport_lba_64(cdb);

                if (sbc_check_dpofua(dev, cmd, cdb))
                        return TCM_INVALID_CDB_FIELD;

                ret = sbc_check_prot(dev, cmd, cdb, sectors, false);
                if (ret)
                        return ret;

                cmd->se_cmd_flags |= SCF_SCSI_DATA_CDB;
                cmd->execute_cmd = sbc_execute_rw;
                break;
        case WRITE_6:
                sectors = transport_get_sectors_6(cdb);
                cmd->t_task_lba = transport_lba_21(cdb);
                cmd->se_cmd_flags |= SCF_SCSI_DATA_CDB;
                cmd->execute_cmd = sbc_execute_rw;
                break;
        case WRITE_10:
        case WRITE_VERIFY:
                sectors = transport_get_sectors_10(cdb);
                cmd->t_task_lba = transport_lba_32(cdb);

                if (sbc_check_dpofua(dev, cmd, cdb))
                        return TCM_INVALID_CDB_FIELD;

                ret = sbc_check_prot(dev, cmd, cdb, sectors, true);
                if (ret)
                        return ret;

                cmd->se_cmd_flags |= SCF_SCSI_DATA_CDB;
                cmd->execute_cmd = sbc_execute_rw;
                break;
        case WRITE_12:
                sectors = transport_get_sectors_12(cdb);
                cmd->t_task_lba = transport_lba_32(cdb);

                if (sbc_check_dpofua(dev, cmd, cdb))
                        return TCM_INVALID_CDB_FIELD;

                ret = sbc_check_prot(dev, cmd, cdb, sectors, true);
                if (ret)
                        return ret;

                cmd->se_cmd_flags |= SCF_SCSI_DATA_CDB;
                cmd->execute_cmd = sbc_execute_rw;
                break;
        case WRITE_16:
        case WRITE_VERIFY_16:
                sectors = transport_get_sectors_16(cdb);
                cmd->t_task_lba = transport_lba_64(cdb);

                if (sbc_check_dpofua(dev, cmd, cdb))
                        return TCM_INVALID_CDB_FIELD;

                ret = sbc_check_prot(dev, cmd, cdb, sectors, true);
                if (ret)
                        return ret;

                cmd->se_cmd_flags |= SCF_SCSI_DATA_CDB;
                cmd->execute_cmd = sbc_execute_rw;
                break;
        case XDWRITEREAD_10:
                if (cmd->data_direction != DMA_TO_DEVICE ||
                    !(cmd->se_cmd_flags & SCF_BIDI))
                        return TCM_INVALID_CDB_FIELD;
                sectors = transport_get_sectors_10(cdb);

                if (sbc_check_dpofua(dev, cmd, cdb))
                        return TCM_INVALID_CDB_FIELD;

                cmd->t_task_lba = transport_lba_32(cdb);
                cmd->se_cmd_flags |= SCF_SCSI_DATA_CDB;

                /*
                 * Setup BIDI XOR callback to be run after I/O completion.
                 */
                cmd->execute_cmd = sbc_execute_rw;
                cmd->transport_complete_callback = &xdreadwrite_callback;
                break;
        case VARIABLE_LENGTH_CMD:
        {
                u16 service_action = get_unaligned_be16(&cdb[8]);
                switch (service_action) {
                case XDWRITEREAD_32:
                        sectors = transport_get_sectors_32(cdb);

                        if (sbc_check_dpofua(dev, cmd, cdb))
                                return TCM_INVALID_CDB_FIELD;
                        /*
                         * Use WRITE_32 and READ_32 opcodes for the emulated
                         * XDWRITE_READ_32 logic.
                         */
                        cmd->t_task_lba = transport_lba_64_ext(cdb);
                        cmd->se_cmd_flags |= SCF_SCSI_DATA_CDB;

                        /*
                         * Setup BIDI XOR callback to be run during after I/O
                         * completion.
                         */
                        cmd->execute_cmd = sbc_execute_rw;
                        cmd->transport_complete_callback = &xdreadwrite_callback;
                        break;
                case WRITE_SAME_32:
                        sectors = transport_get_sectors_32(cdb);
                        if (!sectors) {
                                pr_err("WSNZ=1, WRITE_SAME w/sectors=0 not"
                                       " supported\n");
                                return TCM_INVALID_CDB_FIELD;
                        }

                        size = sbc_get_size(cmd, 1);
                        cmd->t_task_lba = get_unaligned_be64(&cdb[12]);

                        ret = sbc_setup_write_same(cmd, &cdb[10], ops);
                        if (ret)
                                return ret;
                        break;
                default:
                        pr_err("VARIABLE_LENGTH_CMD service action"
                                " 0x%04x not supported\n", service_action);
                        return TCM_UNSUPPORTED_SCSI_OPCODE;
                }
                break;
        }
        case COMPARE_AND_WRITE:
                if (!dev->dev_attrib.emulate_caw) {
                        pr_err_ratelimited("se_device %s/%s (vpd_unit_serial %s) reject COMPARE_AND_WRITE\n",
                                           dev->se_hba->backend->ops->name,
                                           config_item_name(&dev->dev_group.cg_item),
                                           dev->t10_wwn.unit_serial);
                        return TCM_UNSUPPORTED_SCSI_OPCODE;
                }
                sectors = cdb[13];
                /*
                 * Currently enforce COMPARE_AND_WRITE for a single sector
                 */
                if (sectors > 1) {
                        pr_err("COMPARE_AND_WRITE contains NoLB: %u greater"
                               " than 1\n", sectors);
                        return TCM_INVALID_CDB_FIELD;
                }
                if (sbc_check_dpofua(dev, cmd, cdb))
                        return TCM_INVALID_CDB_FIELD;

                /*
                 * Double size because we have two buffers, note that
                 * zero is not an error..
                 */
                size = 2 * sbc_get_size(cmd, sectors);
                cmd->t_task_lba = get_unaligned_be64(&cdb[2]);
                cmd->t_task_nolb = sectors;
                cmd->se_cmd_flags |= SCF_SCSI_DATA_CDB | SCF_COMPARE_AND_WRITE;
                cmd->execute_cmd = sbc_compare_and_write;
                cmd->transport_complete_callback = compare_and_write_callback;
                break;
        case READ_CAPACITY:
                size = READ_CAP_LEN;
                cmd->execute_cmd = sbc_emulate_readcapacity;
                break;
        case SERVICE_ACTION_IN_16:
                switch (cmd->t_task_cdb[1] & 0x1f) {
                case SAI_READ_CAPACITY_16:

                        cmd->execute_cmd = sbc_emulate_readcapacity_16;
                        break;
                case SAI_REPORT_REFERRALS:
                        cmd->execute_cmd = target_emulate_report_referrals;
                        break;
                default:
                        pr_err("Unsupported SA: 0x%02x\n",
                                cmd->t_task_cdb[1] & 0x1f);
                        return TCM_INVALID_CDB_FIELD;
                }
                size = get_unaligned_be32(&cdb[10]);
                break;
        case SYNCHRONIZE_CACHE:
        case SYNCHRONIZE_CACHE_16:
                if (cdb[0] == SYNCHRONIZE_CACHE) {
                        sectors = transport_get_sectors_10(cdb);
                        cmd->t_task_lba = transport_lba_32(cdb);
                } else {
                        sectors = transport_get_sectors_16(cdb);
                        cmd->t_task_lba = transport_lba_64(cdb);
                }
                if (ops->execute_sync_cache) {
                        cmd->execute_cmd = ops->execute_sync_cache;
                        goto check_lba;
                }
                size = 0;
                cmd->execute_cmd = sbc_emulate_noop;
                break;
        case UNMAP:
                if (!ops->execute_unmap)
                        return TCM_UNSUPPORTED_SCSI_OPCODE;

                if (!dev->dev_attrib.emulate_tpu) {
                        pr_err("Got UNMAP, but backend device has"
                               " emulate_tpu disabled\n");
                        return TCM_UNSUPPORTED_SCSI_OPCODE;
                }
                size = get_unaligned_be16(&cdb[7]);
                cmd->execute_cmd = sbc_execute_unmap;
                break;
        case WRITE_SAME_16:
                sectors = transport_get_sectors_16(cdb);
                if (!sectors) {
                        pr_err("WSNZ=1, WRITE_SAME w/sectors=0 not supported\n");
                        return TCM_INVALID_CDB_FIELD;
                }

                size = sbc_get_size(cmd, 1);
                cmd->t_task_lba = get_unaligned_be64(&cdb[2]);

                ret = sbc_setup_write_same(cmd, &cdb[1], ops);
                if (ret)
                        return ret;
                break;
        case WRITE_SAME:
                sectors = transport_get_sectors_10(cdb);
                if (!sectors) {
                        pr_err("WSNZ=1, WRITE_SAME w/sectors=0 not supported\n");
                        return TCM_INVALID_CDB_FIELD;
                }

                size = sbc_get_size(cmd, 1);
                cmd->t_task_lba = get_unaligned_be32(&cdb[2]);

                /*
                 * Follow sbcr26 with WRITE_SAME (10) and check for the existence
                 * of byte 1 bit 3 UNMAP instead of original reserved field
                 */
                ret = sbc_setup_write_same(cmd, &cdb[1], ops);
                if (ret)
                        return ret;
                break;
        case VERIFY:
        case VERIFY_16:
                size = 0;
                if (cdb[0] == VERIFY) {
                        sectors = transport_get_sectors_10(cdb);
                        cmd->t_task_lba = transport_lba_32(cdb);
                } else {
                        sectors = transport_get_sectors_16(cdb);
                        cmd->t_task_lba = transport_lba_64(cdb);
                }
                cmd->execute_cmd = sbc_emulate_noop;
                goto check_lba;
        case REZERO_UNIT:
        case SEEK_6:
        case SEEK_10:
                /*
                 * There are still clients out there which use these old SCSI-2
                 * commands. This mainly happens when running VMs with legacy
                 * guest systems, connected via SCSI command pass-through to
                 * iSCSI targets. Make them happy and return status GOOD.
                 */
                size = 0;
                cmd->execute_cmd = sbc_emulate_noop;
                break;
        case START_STOP:
                size = 0;
                cmd->execute_cmd = sbc_emulate_startstop;
                break;
        default:
                ret = spc_parse_cdb(cmd, &size);
                if (ret)
                        return ret;
        }

        /* reject any command that we don't have a handler for */
        if (!cmd->execute_cmd)
                return TCM_UNSUPPORTED_SCSI_OPCODE;

        if (cmd->se_cmd_flags & SCF_SCSI_DATA_CDB) {
                unsigned long long end_lba;
check_lba:
                end_lba = dev->transport->get_blocks(dev) + 1;
                if (((cmd->t_task_lba + sectors) < cmd->t_task_lba) ||
                    ((cmd->t_task_lba + sectors) > end_lba)) {
                        pr_err("cmd exceeds last lba %llu "
                                "(lba %llu, sectors %u)\n",
                                end_lba, cmd->t_task_lba, sectors);
                        return TCM_ADDRESS_OUT_OF_RANGE;
                }

                if (!(cmd->se_cmd_flags & SCF_COMPARE_AND_WRITE))
                        size = sbc_get_size(cmd, sectors);
        }

        return target_cmd_size_check(cmd, size);
}
EXPORT_SYMBOL(sbc_parse_cdb);

u32 sbc_get_device_type(struct se_device *dev)
{
        return TYPE_DISK;
}
EXPORT_SYMBOL(sbc_get_device_type);

static sense_reason_t
sbc_execute_unmap(struct se_cmd *cmd)
{
        struct sbc_ops *ops = cmd->protocol_data;
        struct se_device *dev = cmd->se_dev;
        unsigned char *buf, *ptr = NULL;
        sector_t lba;
        int size;
        u32 range;
        sense_reason_t ret = 0;
        int dl, bd_dl;

        /* We never set ANC_SUP */
        if (cmd->t_task_cdb[1])
                return TCM_INVALID_CDB_FIELD;

        if (cmd->data_length == 0) {
                target_complete_cmd(cmd, SAM_STAT_GOOD);
                return 0;
        }

        if (cmd->data_length < 8) {
                pr_warn("UNMAP parameter list length %u too small\n",
                        cmd->data_length);
                return TCM_PARAMETER_LIST_LENGTH_ERROR;
        }

        buf = transport_kmap_data_sg(cmd);
        if (!buf)
                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;

        dl = get_unaligned_be16(&buf[0]);
        bd_dl = get_unaligned_be16(&buf[2]);

        size = cmd->data_length - 8;
        if (bd_dl > size)
                pr_warn("UNMAP parameter list length %u too small, ignoring bd_dl %u\n",
                        cmd->data_length, bd_dl);
        else
                size = bd_dl;

        if (size / 16 > dev->dev_attrib.max_unmap_block_desc_count) {
                ret = TCM_INVALID_PARAMETER_LIST;
                goto err;
        }

        /* First UNMAP block descriptor starts at 8 byte offset */
        ptr = &buf[8];
        pr_debug("UNMAP: Sub: %s Using dl: %u bd_dl: %u size: %u"
                " ptr: %p\n", dev->transport->name, dl, bd_dl, size, ptr);

        while (size >= 16) {
                lba = get_unaligned_be64(&ptr[0]);
                range = get_unaligned_be32(&ptr[8]);
                pr_debug("UNMAP: Using lba: %llu and range: %u\n",
                                 (unsigned long long)lba, range);

                if (range > dev->dev_attrib.max_unmap_lba_count) {
                        ret = TCM_INVALID_PARAMETER_LIST;
                        goto err;
                }

                if (lba + range > dev->transport->get_blocks(dev) + 1) {
                        ret = TCM_ADDRESS_OUT_OF_RANGE;
                        goto err;
                }

                if (range) {
                        ret = ops->execute_unmap(cmd, lba, range);
                        if (ret)
                                goto err;
                }

                ptr += 16;
                size -= 16;
        }

err:
        transport_kunmap_data_sg(cmd);
        if (!ret)
                target_complete_cmd(cmd, GOOD);
        return ret;
}

void
sbc_dif_generate(struct se_cmd *cmd)
{
        struct se_device *dev = cmd->se_dev;
        struct t10_pi_tuple *sdt;
        struct scatterlist *dsg = cmd->t_data_sg, *psg;
        sector_t sector = cmd->t_task_lba;
        void *daddr, *paddr;
        int i, j, offset = 0;
        unsigned int block_size = dev->dev_attrib.block_size;

        for_each_sg(cmd->t_prot_sg, psg, cmd->t_prot_nents, i) {
                paddr = kmap_atomic(sg_page(psg)) + psg->offset;
                daddr = kmap_atomic(sg_page(dsg)) + dsg->offset;

                for (j = 0; j < psg->length;
                                j += sizeof(*sdt)) {
                        __u16 crc;
                        unsigned int avail;

                        if (offset >= dsg->length) {
                                offset -= dsg->length;
                                kunmap_atomic(daddr - dsg->offset);
                                dsg = sg_next(dsg);
                                if (!dsg) {
                                        kunmap_atomic(paddr - psg->offset);
                                        return;
                                }
                                daddr = kmap_atomic(sg_page(dsg)) + dsg->offset;
                        }

                        sdt = paddr + j;
                        avail = min(block_size, dsg->length - offset);
                        crc = crc_t10dif(daddr + offset, avail);
                        if (avail < block_size) {
                                kunmap_atomic(daddr - dsg->offset);
                                dsg = sg_next(dsg);
                                if (!dsg) {
                                        kunmap_atomic(paddr - psg->offset);
                                        return;
                                }
                                daddr = kmap_atomic(sg_page(dsg)) + dsg->offset;
                                offset = block_size - avail;
                                crc = crc_t10dif_update(crc, daddr, offset);
                        } else {
                                offset += block_size;
                        }

                        sdt->guard_tag = cpu_to_be16(crc);
                        if (cmd->prot_type == TARGET_DIF_TYPE1_PROT)
                                sdt->ref_tag = cpu_to_be32(sector & 0xffffffff);
                        sdt->app_tag = 0;

                        pr_debug("DIF %s INSERT sector: %llu guard_tag: 0x%04x"
                                 " app_tag: 0x%04x ref_tag: %u\n",
                                 (cmd->data_direction == DMA_TO_DEVICE) ?
                                 "WRITE" : "READ", (unsigned long long)sector,
                                 sdt->guard_tag, sdt->app_tag,
                                 be32_to_cpu(sdt->ref_tag));

                        sector++;
                }

                kunmap_atomic(daddr - dsg->offset);
                kunmap_atomic(paddr - psg->offset);
        }
}

static sense_reason_t
sbc_dif_v1_verify(struct se_cmd *cmd, struct t10_pi_tuple *sdt,
                  __u16 crc, sector_t sector, unsigned int ei_lba)
{
        __be16 csum;

        if (!(cmd->prot_checks & TARGET_DIF_CHECK_GUARD))
                goto check_ref;

        csum = cpu_to_be16(crc);

        if (sdt->guard_tag != csum) {
                pr_err("DIFv1 checksum failed on sector %llu guard tag 0x%04x"
                        " csum 0x%04x\n", (unsigned long long)sector,
                        be16_to_cpu(sdt->guard_tag), be16_to_cpu(csum));
                return TCM_LOGICAL_BLOCK_GUARD_CHECK_FAILED;
        }

check_ref:
        if (!(cmd->prot_checks & TARGET_DIF_CHECK_REFTAG))
                return 0;

        if (cmd->prot_type == TARGET_DIF_TYPE1_PROT &&
            be32_to_cpu(sdt->ref_tag) != (sector & 0xffffffff)) {
                pr_err("DIFv1 Type 1 reference failed on sector: %llu tag: 0x%08x"
                       " sector MSB: 0x%08x\n", (unsigned long long)sector,
                       be32_to_cpu(sdt->ref_tag), (u32)(sector & 0xffffffff));
                return TCM_LOGICAL_BLOCK_REF_TAG_CHECK_FAILED;
        }

        if (cmd->prot_type == TARGET_DIF_TYPE2_PROT &&
            be32_to_cpu(sdt->ref_tag) != ei_lba) {
                pr_err("DIFv1 Type 2 reference failed on sector: %llu tag: 0x%08x"
                       " ei_lba: 0x%08x\n", (unsigned long long)sector,
                        be32_to_cpu(sdt->ref_tag), ei_lba);
                return TCM_LOGICAL_BLOCK_REF_TAG_CHECK_FAILED;
        }

        return 0;
}

void sbc_dif_copy_prot(struct se_cmd *cmd, unsigned int sectors, bool read,
                       struct scatterlist *sg, int sg_off)
{
        struct se_device *dev = cmd->se_dev;
        struct scatterlist *psg;
        void *paddr, *addr;
        unsigned int i, len, left;
        unsigned int offset = sg_off;

        if (!sg)
                return;

        left = sectors * dev->prot_length;

        for_each_sg(cmd->t_prot_sg, psg, cmd->t_prot_nents, i) {
                unsigned int psg_len, copied = 0;

                paddr = kmap_atomic(sg_page(psg)) + psg->offset;
                psg_len = min(left, psg->length);
                while (psg_len) {
                        len = min(psg_len, sg->length - offset);
                        addr = kmap_atomic(sg_page(sg)) + sg->offset + offset;

                        if (read)
                                memcpy(paddr + copied, addr, len);
                        else
                                memcpy(addr, paddr + copied, len);

                        left -= len;
                        offset += len;
                        copied += len;
                        psg_len -= len;

                        kunmap_atomic(addr - sg->offset - offset);

                        if (offset >= sg->length) {
                                sg = sg_next(sg);
                                offset = 0;
                        }
                }
                kunmap_atomic(paddr - psg->offset);
        }
}
EXPORT_SYMBOL(sbc_dif_copy_prot);

sense_reason_t
sbc_dif_verify(struct se_cmd *cmd, sector_t start, unsigned int sectors,
               unsigned int ei_lba, struct scatterlist *psg, int psg_off)
{
        struct se_device *dev = cmd->se_dev;
        struct t10_pi_tuple *sdt;
        struct scatterlist *dsg = cmd->t_data_sg;
        sector_t sector = start;
        void *daddr, *paddr;
        int i;
        sense_reason_t rc;
        int dsg_off = 0;
        unsigned int block_size = dev->dev_attrib.block_size;

        for (; psg && sector < start + sectors; psg = sg_next(psg)) {
                paddr = kmap_atomic(sg_page(psg)) + psg->offset;
                daddr = kmap_atomic(sg_page(dsg)) + dsg->offset;

                for (i = psg_off; i < psg->length &&
                                sector < start + sectors;
                                i += sizeof(*sdt)) {
                        __u16 crc;
                        unsigned int avail;

                        if (dsg_off >= dsg->length) {
                                dsg_off -= dsg->length;
                                kunmap_atomic(daddr - dsg->offset);
                                dsg = sg_next(dsg);
                                if (!dsg) {
                                        kunmap_atomic(paddr - psg->offset);
                                        return 0;
                                }
                                daddr = kmap_atomic(sg_page(dsg)) + dsg->offset;
                        }

                        sdt = paddr + i;

                        pr_debug("DIF READ sector: %llu guard_tag: 0x%04x"
                                 " app_tag: 0x%04x ref_tag: %u\n",
                                 (unsigned long long)sector, sdt->guard_tag,
                                 sdt->app_tag, be32_to_cpu(sdt->ref_tag));

                        if (sdt->app_tag == T10_PI_APP_ESCAPE) {
                                dsg_off += block_size;
                                goto next;
                        }

                        avail = min(block_size, dsg->length - dsg_off);
                        crc = crc_t10dif(daddr + dsg_off, avail);
                        if (avail < block_size) {
                                kunmap_atomic(daddr - dsg->offset);
                                dsg = sg_next(dsg);
                                if (!dsg) {
                                        kunmap_atomic(paddr - psg->offset);
                                        return 0;
                                }
                                daddr = kmap_atomic(sg_page(dsg)) + dsg->offset;
                                dsg_off = block_size - avail;
                                crc = crc_t10dif_update(crc, daddr, dsg_off);
                        } else {
                                dsg_off += block_size;
                        }

                        rc = sbc_dif_v1_verify(cmd, sdt, crc, sector, ei_lba);
                        if (rc) {
                                kunmap_atomic(daddr - dsg->offset);
                                kunmap_atomic(paddr - psg->offset);
                                cmd->bad_sector = sector;
                                return rc;
                        }
next:
                        sector++;
                        ei_lba++;
                }

                psg_off = 0;
                kunmap_atomic(daddr - dsg->offset);
                kunmap_atomic(paddr - psg->offset);
        }

        return 0;
}
EXPORT_SYMBOL(sbc_dif_verify);