Forwarding targets attribute added

See the patch for description



git-svn-id: http://svn.code.sf.net/p/scst/svn/trunk@6209 d57e44dd-8a1f-0410-8b47-8ef2f437770f

scst/README

@@ -665,6 +665,10 @@ Every target should have at least the following entries:
    until rel_tgt_id becomes unique. This attribute initialized unique by
    SCST by default.
 
+ - forwarding - if set this target is forwarding target, i.e. does not check
+   any local SCSI events (reservations, etc.). Those event supposed to
+   be checked on the another, requester's side.
+
  - *count*, e.g. read_io_count_kb, - statistics about executed
    commands and transferred data. Those attributes have speaking names
    built from parts:

scst/README_in-tree

@@ -541,6 +541,10 @@ Every target should have at least the following entries:
    until rel_tgt_id becomes unique. This attribute initialized unique by
    SCST by default.
 
+ - forwarding - if set this target is forwarding target, i.e. does not check
+   any local SCSI events (reservations, etc.). Those event supposed to
+   be checked on the another, requester's side.
+
  - *count*, e.g. read_io_count_kb, - statistics about executed
    commands and transferred data. Those attributes have speaking names
    built from parts:

scst/include/scst.h

@@ -702,6 +702,9 @@ enum scst_exec_context {
 /* Cache of acg->acg_black_hole_type */
 #define SCST_TGT_DEV_BLACK_HOLE		1
 
+/* Cache of tgt->tgt_forwarding */
+#define SCST_TGT_DEV_FORWARDING		5
+
 /*************************************************************
  ** I/O grouping types. Changing them don't forget to change
  ** the corresponding *_STR values in scst_const.h!
@@ -1926,6 +1929,13 @@ struct scst_tgt {
 	struct list_head tgt_acg_list; /* target ACG groups */
 #endif
 
+	/*
+	 * Set, if this target is forwarding target, i.e. does not check
+	 * any local SCSI events (reservations, etc.). Those event supposed
+	 * to be checked on the another, requester's side.
+	 */
+	unsigned tgt_forwarding:1;
+
 	/* Per target analog of the corresponding driver's fields */
 	unsigned tgt_dif_supported:1;
 	unsigned tgt_hw_dif_type1_supported:1;

scst/src/scst_lib.c

@@ -4858,6 +4858,10 @@ static int scst_alloc_add_tgt_dev(struct scst_session *sess,
 	tgt_dev->lun = acg_dev->lun;
 	tgt_dev->acg_dev = acg_dev;
 	tgt_dev->tgt_dev_rd_only = acg_dev->acg_dev_rd_only || dev->dev_rd_only;
+	if (sess->tgt->tgt_forwarding)
+		set_bit(SCST_TGT_DEV_FORWARDING, &tgt_dev->tgt_dev_flags);
+	else
+		clear_bit(SCST_TGT_DEV_FORWARDING, &tgt_dev->tgt_dev_flags);
 	tgt_dev->hw_dif_same_sg_layout_required = sess->tgt->tgt_hw_dif_same_sg_layout_required;
 	tgt_dev->tgt_dev_dif_guard_format = acg_dev->acg_dev_dif_guard_format;
 	if (tgt_dev->tgt_dev_dif_guard_format == SCST_DIF_GUARD_FORMAT_IP)

scst/src/scst_pres.c

@@ -1535,6 +1535,11 @@ static int scst_pr_register_all_tg_pt(struct scst_cmd *cmd, uint8_t *buffer,
 				continue;
 			if (tgt->rel_tgt_id == 0)
 				continue;
+			if (tgt->tgt_forwarding) {
+				TRACE_PR("ALL_TG_PT: skipping forwarding "
+					"target %s", tgt->tgt_name);
+				continue;
+			}
 			TRACE_PR("tgt %s, rel_tgt_id %d", tgt->tgt_name,
 				tgt->rel_tgt_id);
 			res = scst_pr_register_on_tgt_id(cmd, tgt->rel_tgt_id,

scst/src/scst_sysfs.c

@@ -2498,6 +2498,95 @@ static struct kobj_attribute scst_rel_tgt_id =
 	__ATTR(rel_tgt_id, S_IRUGO | S_IWUSR, scst_rel_tgt_id_show,
 	       scst_rel_tgt_id_store);
 
+static ssize_t scst_tgt_forwarding_show(struct kobject *kobj,
+	struct kobj_attribute *attr, char *buf)
+{
+	struct scst_tgt *tgt;
+	int res;
+
+	TRACE_ENTRY();
+
+	tgt = container_of(kobj, struct scst_tgt, tgt_kobj);
+
+	res = sprintf(buf, "%d\n%s", tgt->tgt_forwarding,
+			tgt->tgt_forwarding ? SCST_SYSFS_KEY_MARK "\n" : "");
+
+	TRACE_EXIT_RES(res);
+	return res;
+}
+
+static ssize_t scst_tgt_forwarding_store(struct kobject *kobj,
+	struct kobj_attribute *attr, const char *buf, size_t count)
+{
+	int res = 0;
+	struct scst_tgt *tgt;
+	struct scst_session *sess;
+	int old;
+
+	TRACE_ENTRY();
+
+	if ((buf == NULL) || (count == 0)) {
+		res = 0;
+		goto out;
+	}
+
+	tgt = container_of(kobj, struct scst_tgt, tgt_kobj);
+
+	mutex_lock(&scst_mutex);
+
+	old = tgt->tgt_forwarding;
+
+	switch (buf[0]) {
+	case '0':
+		tgt->tgt_forwarding = 0;
+		break;
+	case '1':
+		tgt->tgt_forwarding = 1;
+		break;
+	default:
+		PRINT_ERROR("%s: Requested action not understood: %s",
+		       __func__, buf);
+		res = -EINVAL;
+		goto out_unlock;
+	}
+
+	if (tgt->tgt_forwarding == old)
+		goto out_unlock;
+
+	list_for_each_entry(sess, &tgt->sess_list, sess_list_entry) {
+		int i;
+		for (i = 0; i < SESS_TGT_DEV_LIST_HASH_SIZE; i++) {
+			struct list_head *head = &sess->sess_tgt_dev_list[i];
+			struct scst_tgt_dev *tgt_dev;
+			list_for_each_entry(tgt_dev, head, sess_tgt_dev_list_entry) {
+				if (tgt->tgt_forwarding)
+					set_bit(SCST_TGT_DEV_FORWARDING, &tgt_dev->tgt_dev_flags);
+				else
+					clear_bit(SCST_TGT_DEV_FORWARDING, &tgt_dev->tgt_dev_flags);
+			}
+		}
+	}
+
+	if (tgt->tgt_forwarding)
+		PRINT_INFO("Set target %s as forwarding", tgt->tgt_name);
+	else
+		PRINT_INFO("Clear target %s as forwarding", tgt->tgt_name);
+
+out_unlock:
+	mutex_unlock(&scst_mutex);
+
+	if (res == 0)
+		res = count;
+
+out:
+	TRACE_EXIT_RES(res);
+	return res;
+}
+
+static struct kobj_attribute scst_tgt_forwarding =
+	__ATTR(forwarding, S_IRUGO | S_IWUSR, scst_tgt_forwarding_show,
+	       scst_tgt_forwarding_store);
+
 static ssize_t scst_tgt_comment_show(struct kobject *kobj,
 	struct kobj_attribute *attr, char *buf)
 {
@@ -2769,6 +2858,7 @@ SCST_TGT_SYSFS_STAT_ATTR(cmd_count, none_cmd_count, SCST_DATA_NONE, >> 0);
 
 static struct attribute *scst_tgt_attrs[] = {
 	&scst_rel_tgt_id.attr,
+	&scst_tgt_forwarding.attr,
 	&scst_tgt_comment.attr,
 	&scst_tgt_addr_method.attr,
 	&scst_tgt_io_grouping_type.attr,

scst/src/scst_targ.c

@@ -2789,6 +2789,15 @@ int __scst_check_local_events(struct scst_cmd *cmd, bool preempt_tests_only)
 		goto out;
 	}
 
+	if (unlikely(test_bit(SCST_TGT_DEV_FORWARDING, &cmd->tgt_dev->tgt_dev_flags))) {
+		/*
+		 * All the checks are supposed to be done on the
+		 * forwarding requester's side.
+		 */
+		res = 0;
+		goto out;
+	}
+
 	/*
 	 * There's no race here, because we need to trace commands sent
 	 * *after* dev_double_ua_possible flag was set.