[PATCH 3/4] zfcp: trace return values of sysfs unit add store

[Nihar Panda <niharp@linux.ibm.com>]

From: Chinmaya Kajagar <chinmayk@linux.ibm.com>

Sysfs unit add failures are seen during FCP devices manual SCSI LUN
scans, indicating the kernel cannot add a LUN, usually because the
device is offline, already exists, no memory or the target port is
incorrectly configured.

Add a new trace to debug zfcp sysfs unit add failures with tag id
ZFCP_DBF_HBA_UAS. This traces wwpn, fcp lun id, return value (error
condition) and associated hba of the device.

Typical unit add store failures as seen below example syslog messages,

Feb  2 10:47:25 systemd-udevd[823]: rport-1:0-2: /etc/udev/
rules.d/41-zfcp-lun-0.0.50c0:0x500507680b26c449:0x01d2000000000000.rules:10
Failed to write ATTR{/sys/devices/css0/0.0.0015/0.0.50c0/0x500507680b26c449
/unit_add}, ignoring: File exists

Feb  2 10:50:03 systemd-udevd[801]: rport-2:0-3: /etc/udev/
rules.d/41-zfcp-lun-0.0.50c0:0x500507680b26c448:0x01d2000000000000.rules:10
Failed to write ATTR{/sys/devices/css0/0.0.0015/0.0.50c0/0x500507680b26c448
/unit_add}, ignoring: Cannot allocate memory

Example zfcpdbf traces for both the errors:

Timestamp      : 2026-03-05-07:28:34:029797
Area           : HBA
Subarea        : 00
Level          : 3
Exception      : -
CPU ID         : 0002
Caller         : 0x000001fe345e6d0e
Record ID      : 6
Tag            : syuast2
Description    : syuast2 HBA, unit add, failed, unable to add unit
Request ID     : 0x00000000ffffffff
Request status : 0xffffffff
FSF cmnd       : 0xffffffff
FSF sequence no: 0xffffffff
WWPN           : 0x500507680b25c448
LUN            : 0x01d3000000000000
Return Value   : 0xfffffff4

Timestamp      : 2026-03-05-07:33:04:151807 <== the last record
Area           : HBA
Subarea        : 00
Level          : 3
Exception      : -
CPU ID         : 0002
Caller         : 0x000001fe345e6d0e
Record ID      : 6
Tag            : syuast2
Description    : syuast2 HBA, unit add, failed, unable to add unit
Request ID     : 0x00000000ffffffff
Request status : 0xffffffff
FSF cmnd       : 0xffffffff
FSF sequence no: 0xffffffff
WWPN           : 0x500507680b25c449
LUN            : 0x01d0000000000000
Return Value   : 0xfffffff4

Signed-off-by: Chinmaya Kajagar <chinmayk@linux.ibm.com>
---
 drivers/s390/scsi/zfcp_dbf.c   | 36 ++++++++++++++++++++++++++++++++++
 drivers/s390/scsi/zfcp_dbf.h   | 16 +++++++++++++++
 drivers/s390/scsi/zfcp_ext.h   |  4 +++-
 drivers/s390/scsi/zfcp_sysfs.c | 17 +++++++++++-----
 4 files changed, 67 insertions(+), 6 deletions(-)

diff --git a/drivers/s390/scsi/zfcp_dbf.c b/drivers/s390/scsi/zfcp_dbf.c
index 4217b74baa38..81fb8af408e9 100644
--- a/drivers/s390/scsi/zfcp_dbf.c
+++ b/drivers/s390/scsi/zfcp_dbf.c
@@ -265,6 +265,42 @@ void zfcp_dbf_hba_fsf_uss(char *tag, struct zfcp_fsf_req *req)
 	spin_unlock_irqrestore(&dbf->hba_lock, flags);
 }
 
+/**
+ * zfcp_dbf_hba_uas - trace event for sysfs unit add store
+ * @tag: tag indicating which kind of unit add store condition occurred
+ * @level: debug trace level
+ * @adapter: pointer to struct zfcp_adapter
+ * @wwpn: remote port wwn
+ * @fcp_lun: FCP LUN
+ * @ret: return value
+ */
+void zfcp_dbf_hba_uas(char *tag, int level, struct zfcp_adapter *adapter,
+		      u64 wwpn, u64 fcp_lun, int ret)
+{
+	struct zfcp_dbf *dbf = adapter->dbf;
+	struct zfcp_dbf_hba *rec = &dbf->hba_buf;
+	unsigned long flags;
+
+	if (unlikely(!debug_level_enabled(dbf->hba, level)))
+		return;
+
+	spin_lock_irqsave(&dbf->hba_lock, flags);
+	memset(rec, 0, sizeof(*rec));
+
+	memcpy(rec->tag, tag, ZFCP_DBF_TAG_LEN);
+	rec->id = ZFCP_DBF_HBA_UAS;
+	rec->fsf_req_id = ~0u;
+	rec->fsf_req_status = ~0u;
+	rec->fsf_cmd = ~0u;
+	rec->fsf_seq_no = ~0u;
+	rec->u.uas.wwpn = wwpn;
+	rec->u.uas.fcp_lun = fcp_lun;
+	rec->u.uas.ret = ret;
+
+	debug_event(dbf->hba, level, rec, sizeof(*rec));
+	spin_unlock_irqrestore(&dbf->hba_lock, flags);
+}
+
 /**
  * zfcp_dbf_hba_bit_err - trace event for bit error conditions
  * @tag: tag indicating which kind of bit error unsolicited status was received
diff --git a/drivers/s390/scsi/zfcp_dbf.h b/drivers/s390/scsi/zfcp_dbf.h
index c84f076440a8..79973fb24b1c 100644
--- a/drivers/s390/scsi/zfcp_dbf.h
+++ b/drivers/s390/scsi/zfcp_dbf.h
@@ -174,6 +174,18 @@ struct zfcp_dbf_hba_uss {
 	u8 res4[20];
 } __packed;
 
+/**
+ * struct zfcp_dbf_hba_uas - trace record for sysfs unit add store
+ * @wwpn: remote port wwn
+ * @fcp_lun: FCP LUN
+ * @ret: return value
+ */
+struct zfcp_dbf_hba_uas {
+	u64 wwpn;
+	u64 fcp_lun;
+	u32 ret;
+} __packed;
+
 /**
  * struct zfcp_dbf_hba_fces - trace record for FC Endpoint Security
  * @req_issued: timestamp when request was issued
@@ -200,6 +212,7 @@ struct zfcp_dbf_hba_fces {
  * @ZFCP_DBF_HBA_BIT: bit error trace record
  * @ZFCP_DBF_HBA_BASIC: basic adapter event, only trace tag, no other data
  * @ZFCP_DBF_HBA_FCES: FC Endpoint Security trace record
+ * @ZFCP_DBF_HBA_UAS: unit add store trace record
  */
 enum zfcp_dbf_hba_id {
 	ZFCP_DBF_HBA_RES	= 1,
@@ -207,6 +220,7 @@ enum zfcp_dbf_hba_id {
 	ZFCP_DBF_HBA_BIT	= 3,
 	ZFCP_DBF_HBA_BASIC	= 4,
 	ZFCP_DBF_HBA_FCES	= 5,
+	ZFCP_DBF_HBA_UAS        = 6,
 };
 
 /**
@@ -223,6 +237,7 @@ enum zfcp_dbf_hba_id {
  * @u.uss:  data for unsolicited status buffer
  * @u.be:   data for bit error unsolicited status buffer
  * @u.fces: data for FC Endpoint Security
+ * @u.uas:  data for unit add store
  */
 struct zfcp_dbf_hba {
 	u8 id;
@@ -237,6 +252,7 @@ struct zfcp_dbf_hba {
 		struct zfcp_dbf_hba_uss uss;
 		struct fsf_bit_error_payload be;
 		struct zfcp_dbf_hba_fces fces;
+		struct zfcp_dbf_hba_uas uas;
 	} u;
 } __packed;
 
diff --git a/drivers/s390/scsi/zfcp_ext.h b/drivers/s390/scsi/zfcp_ext.h
index 9f5152b42b0e..40bd597fb4cd 100644
--- a/drivers/s390/scsi/zfcp_ext.h
+++ b/drivers/s390/scsi/zfcp_ext.h
@@ -4,7 +4,7 @@
  *
  * External function declarations.
  *
- * Copyright IBM Corp. 2002, 2023
+ * Copyright IBM Corp. 2002, 2026
  */
 
 #ifndef ZFCP_EXT_H
@@ -49,6 +49,8 @@ extern void zfcp_dbf_hba_fsf_fces(char *tag, const struct zfcp_fsf_req *req,
 extern void zfcp_dbf_hba_fsf_reqid(const char *const tag, const int level,
 				   struct zfcp_adapter *const adapter,
 				   const u64 req_id);
+extern void zfcp_dbf_hba_uas(char *tag, int level, struct zfcp_adapter *adapter,
+			     u64 wwpn, u64 fcp_lun, int ret);
 extern void zfcp_dbf_hba_bit_err(char *, struct zfcp_fsf_req *);
 extern void zfcp_dbf_hba_def_err(struct zfcp_adapter *, u64, u16, void **);
 extern void zfcp_dbf_san_req(char *, struct zfcp_fsf_req *, u32);
diff --git a/drivers/s390/scsi/zfcp_sysfs.c b/drivers/s390/scsi/zfcp_sysfs.c
index 42423549e511..729c9664a48f 100644
--- a/drivers/s390/scsi/zfcp_sysfs.c
+++ b/drivers/s390/scsi/zfcp_sysfs.c
@@ -4,7 +4,7 @@
  *
  * sysfs attributes.
  *
- * Copyright IBM Corp. 2008, 2020
+ * Copyright IBM Corp. 2008, 2026
  */
 
 #define pr_fmt(fmt) "zfcp: " fmt
@@ -442,17 +442,24 @@ static ssize_t zfcp_sysfs_unit_add_store(struct device *dev,
 					 const char *buf, size_t count)
 {
 	struct zfcp_port *port = container_of(dev, struct zfcp_port, dev);
+	struct zfcp_adapter *adapter = port->adapter;
 	u64 fcp_lun;
-	int retval;
+	int retval = -EINVAL;
 
-	if (kstrtoull(buf, 0, (unsigned long long *) &fcp_lun))
-		return -EINVAL;
+	if (kstrtoull(buf, 0, (unsigned long long *)&fcp_lun)) {
+		zfcp_dbf_hba_uas("syuast1", 3, adapter, port->wwpn,
+				 fcp_lun, retval);
+		return retval;
+	}
 
 	flush_work(&port->rport_work);
 
 	retval = zfcp_unit_add(port, fcp_lun);
-	if (retval)
+	if (retval) {
+		zfcp_dbf_hba_uas("syuast2", 3, adapter, port->wwpn,
+				 fcp_lun, retval);
 		return retval;
+	}
 
 	return count;
 }
-- 
2.53.0