scsi: target: core: Move buffer clearing hack

Move the hack to clear some buffers to transport_handle_cdb_direct() so we
can eventually merge transport_handle_cdb_direct() and target_submit().

This also fixes up the comment so it's clear it was only for udev and
reflects that the referenced function does not exist and we now allow more
than 1 page for control CDBs.

Signed-off-by: Mike Christie <michael.christie@oracle.com>
Link: https://lore.kernel.org/r/20230928020907.5730-4-michael.christie@oracle.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/target/target_core_transport.c

@@ -1592,6 +1592,27 @@ int transport_handle_cdb_direct(
 	 */
 	core_alua_check_nonop_delay(cmd);
 
+	if (cmd->t_data_nents != 0) {
+		/*
+		 * This is primarily a hack for udev and tcm loop which sends
+		 * INQUIRYs with a single page and expects the data to be
+		 * cleared.
+		 */
+		if (!(cmd->se_cmd_flags & SCF_SCSI_DATA_CDB) &&
+		    cmd->data_direction == DMA_FROM_DEVICE) {
+			struct scatterlist *sgl = cmd->t_data_sg;
+			unsigned char *buf = NULL;
+
+			BUG_ON(!sgl);
+
+			buf = kmap_local_page(sg_page(sgl));
+			if (buf) {
+				memset(buf + sgl->offset, 0, sgl->length);
+				kunmap_local(buf);
+			}
+		}
+	}
+
 	if (!cmd->se_lun) {
 		dump_stack();
 		pr_err("cmd->se_lun is NULL\n");
@@ -1795,34 +1816,6 @@ EXPORT_SYMBOL_GPL(target_submit_prep);
  */
 void target_submit(struct se_cmd *se_cmd)
 {
-	struct scatterlist *sgl = se_cmd->t_data_sg;
-	unsigned char *buf = NULL;
-
-	might_sleep();
-
-	if (se_cmd->t_data_nents != 0) {
-		BUG_ON(!sgl);
-		/*
-		 * A work-around for tcm_loop as some userspace code via
-		 * scsi-generic do not memset their associated read buffers,
-		 * so go ahead and do that here for type non-data CDBs.  Also
-		 * note that this is currently guaranteed to be a single SGL
-		 * for this case by target core in target_setup_cmd_from_cdb()
-		 * -> transport_generic_cmd_sequencer().
-		 */
-		if (!(se_cmd->se_cmd_flags & SCF_SCSI_DATA_CDB) &&
-		     se_cmd->data_direction == DMA_FROM_DEVICE) {
-			if (sgl)
-				buf = kmap(sg_page(sgl)) + sgl->offset;
-
-			if (buf) {
-				memset(buf, 0, sgl->length);
-				kunmap(sg_page(sgl));
-			}
-		}
-
-	}
-
 	transport_handle_cdb_direct(se_cmd);
 }
 EXPORT_SYMBOL_GPL(target_submit);