target/sbc: Seperate WRITE_SAME based on UNMAP flag in sbc_ops

This patch adds a new sbc_ops->execute_write_same_unmap() caller for use
with WRITE_SAME w/ UNMAP=1, and performs the ->execute_cmd() setup based
this bit within sbc_setup_write_same() code.

Also, makes the changes in sbc_parse_cdb() to handle a sense_reason_t
return from sbc_setup_write_same() on error.

Reported-by: Christoph Hellwig <hch@lst.de>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

2 files changed, 24 insertions, 28 deletions

diff --git a/drivers/target/target_core_sbc.c b/drivers/target/target_core_sbc.c
index b8024219cd4f..a5a8f463004b 100644
--- a/drivers/target/target_core_sbc.c
+++ b/drivers/target/target_core_sbc.c
@@ -235,26 +235,30 @@ static inline unsigned long long transport_lba_64_ext(unsigned char *cdb)
         return ((unsigned long long)__v2) | (unsigned long long)__v1 << 32;
 }
 
-static int sbc_write_same_supported(struct se_device *dev,
-                unsigned char *flags)
+static sense_reason_t
+sbc_setup_write_same(struct se_cmd *cmd, unsigned char *flags, struct sbc_ops *ops)
 {
         if ((flags[0] & 0x04) || (flags[0] & 0x02)) {
                 pr_err("WRITE_SAME PBDATA and LBDATA"
                         " bits not supported for Block Discard"
                         " Emulation\n");
-                return -ENOSYS;
+                return TCM_UNSUPPORTED_SCSI_OPCODE;
         }
-
         /*
-         * Currently for the emulated case we only accept
-         * tpws with the UNMAP=1 bit set.
+         * Special case for WRITE_SAME w/ UNMAP=1 that ends up getting
+         * translated into block discard requests within backend code.
          */
-        if (!(flags[0] & 0x08)) {
-                pr_err("WRITE_SAME w/o UNMAP bit not"
-                        " supported for Block Discard Emulation\n");
-                return -ENOSYS;
+        if (flags[0] & 0x08) {
+                if (!ops->execute_write_same_unmap)
+                        return TCM_UNSUPPORTED_SCSI_OPCODE;
+
+                cmd->execute_cmd = ops->execute_write_same_unmap;
+                return 0;
         }
+        if (!ops->execute_write_same)
+                return TCM_UNSUPPORTED_SCSI_OPCODE;
 
+        cmd->execute_cmd = ops->execute_write_same;
         return 0;
 }
 
@@ -418,9 +422,6 @@ sbc_parse_cdb(struct se_cmd *cmd, struct sbc_ops *ops)
                                 cmd->se_cmd_flags |= SCF_FUA;
                         break;
                 case WRITE_SAME_32:
-                        if (!ops->execute_write_same)
-                                return TCM_UNSUPPORTED_SCSI_OPCODE;
-
                         sectors = transport_get_sectors_32(cdb);
                         if (!sectors) {
                                 pr_err("WSNZ=1, WRITE_SAME w/sectors=0 not"
@@ -431,9 +432,9 @@ sbc_parse_cdb(struct se_cmd *cmd, struct sbc_ops *ops)
                         size = sbc_get_size(cmd, 1);
                         cmd->t_task_lba = get_unaligned_be64(&cdb[12]);
 
-                        if (sbc_write_same_supported(dev, &cdb[10]) < 0)
-                                return TCM_UNSUPPORTED_SCSI_OPCODE;
-                        cmd->execute_cmd = ops->execute_write_same;
+                        ret = sbc_setup_write_same(cmd, &cdb[10], ops);
+                        if (ret < 0)
+                                return ret;
                         break;
                 default:
                         pr_err("VARIABLE_LENGTH_CMD service action"
@@ -495,9 +496,6 @@ sbc_parse_cdb(struct se_cmd *cmd, struct sbc_ops *ops)
                 cmd->execute_cmd = ops->execute_unmap;
                 break;
         case WRITE_SAME_16:
-                if (!ops->execute_write_same)
-                        return TCM_UNSUPPORTED_SCSI_OPCODE;
-
                 sectors = transport_get_sectors_16(cdb);
                 if (!sectors) {
                         pr_err("WSNZ=1, WRITE_SAME w/sectors=0 not supported\n");
@@ -507,14 +505,11 @@ sbc_parse_cdb(struct se_cmd *cmd, struct sbc_ops *ops)
                 size = sbc_get_size(cmd, 1);
                 cmd->t_task_lba = get_unaligned_be64(&cdb[2]);
 
-                if (sbc_write_same_supported(dev, &cdb[1]) < 0)
-                        return TCM_UNSUPPORTED_SCSI_OPCODE;
-                cmd->execute_cmd = ops->execute_write_same;
+                ret = sbc_setup_write_same(cmd, &cdb[1], ops);
+                if (ret < 0)
+                        return ret;
                 break;
         case WRITE_SAME:
-                if (!ops->execute_write_same)
-                        return TCM_UNSUPPORTED_SCSI_OPCODE;
-
                 sectors = transport_get_sectors_10(cdb);
                 if (!sectors) {
                         pr_err("WSNZ=1, WRITE_SAME w/sectors=0 not supported\n");
@@ -528,9 +523,9 @@ sbc_parse_cdb(struct se_cmd *cmd, struct sbc_ops *ops)
                  * Follow sbcr26 with WRITE_SAME (10) and check for the existence
                  * of byte 1 bit 3 UNMAP instead of original reserved field
                  */
-                if (sbc_write_same_supported(dev, &cdb[1]) < 0)
-                        return TCM_UNSUPPORTED_SCSI_OPCODE;
-                cmd->execute_cmd = ops->execute_write_same;
+                ret = sbc_setup_write_same(cmd, &cdb[1], ops);
+                if (ret < 0)
+                        return ret;
                 break;
         case VERIFY:
                 size = 0;
diff --git a/include/target/target_core_backend.h b/include/target/target_core_backend.h
index aa868090b9ab..3393ab10766c 100644
--- a/include/target/target_core_backend.h
+++ b/include/target/target_core_backend.h
@@ -41,6 +41,7 @@ struct sbc_ops {
         sense_reason_t (*execute_rw)(struct se_cmd *cmd);
         sense_reason_t (*execute_sync_cache)(struct se_cmd *cmd);
         sense_reason_t (*execute_write_same)(struct se_cmd *cmd);
+        sense_reason_t (*execute_write_same_unmap)(struct se_cmd *cmd);
         sense_reason_t (*execute_unmap)(struct se_cmd *cmd);
 };