[PATCH 2/6] qla2xxx: Add a generic tracing framework

[Nilesh Javali <njavali@xxxxxxxxxxx>]

From: Arun Easi <aeasi@xxxxxxxxxxx>

Adding a message based tracing mechanism where
a rotating number of messages are captured in
a trace structure. Disable/enable/resize
operations are allowed via debugfs interfaces.

Signed-off-by: Arun Easi <aeasi@xxxxxxxxxxx>
Signed-off-by: Nilesh Javali <njavali@xxxxxxxxxxx>
---
 drivers/scsi/qla2xxx/qla_dbg.c |  12 +++
 drivers/scsi/qla2xxx/qla_dbg.h | 140 +++++++++++++++++++++++++++++++++
 drivers/scsi/qla2xxx/qla_def.h |  31 ++++++++
 drivers/scsi/qla2xxx/qla_dfs.c | 102 ++++++++++++++++++++++++
 drivers/scsi/qla2xxx/qla_os.c  |   5 ++
 5 files changed, 290 insertions(+)

diff --git a/drivers/scsi/qla2xxx/qla_dbg.c b/drivers/scsi/qla2xxx/qla_dbg.c
index 7cf1f78cbaee..c4ba8ac51d27 100644
--- a/drivers/scsi/qla2xxx/qla_dbg.c
+++ b/drivers/scsi/qla2xxx/qla_dbg.c
@@ -2777,3 +2777,15 @@ ql_dbg_qp(uint32_t level, struct qla_qpair *qpair, int32_t id,
 	va_end(va);
 
 }
+
+#ifdef QLA_TRACING
+void qla_tracing_init(void)
+{
+	if (is_kdump_kernel())
+		return;
+}
+
+void qla_tracing_exit(void)
+{
+}
+#endif /* QLA_TRACING */
diff --git a/drivers/scsi/qla2xxx/qla_dbg.h b/drivers/scsi/qla2xxx/qla_dbg.h
index feeb1666227f..e0d91a1f81c0 100644
--- a/drivers/scsi/qla2xxx/qla_dbg.h
+++ b/drivers/scsi/qla2xxx/qla_dbg.h
@@ -5,6 +5,7 @@
  */
 
 #include "qla_def.h"
+#include <linux/delay.h>
 
 /*
  * Firmware Dump structure definition
@@ -321,6 +322,145 @@ struct qla2xxx_fw_dump {
 
 extern uint ql_errlev;
 
+#ifdef QLA_TRACING
+#include <linux/crash_dump.h>
+
+extern void qla_tracing_init(void);
+extern void qla_tracing_exit(void);
+
+static inline int
+ql_mask_match_ext(uint level, int *log_tunable)
+{
+	if (*log_tunable == 1)
+		*log_tunable = QL_DBG_DEFAULT1_MASK;
+
+	return (level & *log_tunable) == level;
+}
+
+static inline int
+__qla_trace_get(struct qla_trace *trc)
+{
+	if (test_bit(QLA_TRACE_QUIESCE, &trc->flags))
+		return -EIO;
+	atomic_inc(&trc->ref_count);
+	return 0;
+}
+
+static inline int
+qla_trace_get(struct qla_trace *trc)
+{
+	unsigned long flags;
+	int ret;
+
+	spin_lock_irqsave(&trc->trc_lock, flags);
+	ret = __qla_trace_get(trc);
+	spin_unlock_irqrestore(&trc->trc_lock, flags);
+
+	return ret;
+}
+
+static inline void
+qla_trace_put(struct qla_trace *trc)
+{
+	wmb();
+	atomic_dec(&trc->ref_count);
+}
+
+static inline char *
+qla_get_trace_next(struct qla_trace *trc)
+{
+	uint32_t t_ind;
+	char *buf;
+	unsigned long flags;
+
+	spin_lock_irqsave(&trc->trc_lock, flags);
+	if (!test_bit(QLA_TRACE_ENABLED, &trc->flags) ||
+	    __qla_trace_get(trc)) {
+		spin_unlock_irqrestore(&trc->trc_lock, flags);
+		return NULL;
+	}
+	t_ind = trc->trace_ind = qla_trace_ind_norm(trc, trc->trace_ind + 1);
+	spin_unlock_irqrestore(&trc->trc_lock, flags);
+
+	if (!t_ind)
+		set_bit(QLA_TRACE_WRAPPED, &trc->flags);
+
+	buf = qla_trace_record(trc, t_ind);
+	/* Put an end marker '>' for the next record. */
+	qla_trace_record(trc, qla_trace_ind_norm(trc, t_ind + 1))[0] = '>';
+
+	return buf;
+}
+
+static inline int
+qla_trace_quiesce(struct qla_trace *trc)
+{
+	unsigned long flags;
+	u32 cnt = 0;
+	int ret = 0;
+
+	set_bit(QLA_TRACE_QUIESCE, &trc->flags);
+
+	spin_lock_irqsave(&trc->trc_lock, flags);
+	while (atomic_read(&trc->ref_count)) {
+		spin_unlock_irqrestore(&trc->trc_lock, flags);
+
+		msleep(1);
+
+		spin_lock_irqsave(&trc->trc_lock, flags);
+		cnt++;
+		if (cnt > 10 * 1000) {
+			pr_info("qla2xxx: Trace could not be quiesced now (count=%d).",
+				atomic_read(&trc->ref_count));
+			/* Leave trace enabled */
+			clear_bit(QLA_TRACE_QUIESCE, &trc->flags);
+			ret = -EIO;
+			break;
+		}
+	}
+	spin_unlock_irqrestore(&trc->trc_lock, flags);
+	return ret;
+}
+
+static inline void
+qla_trace_init(struct qla_trace *trc, char *name, u32 num_entries)
+{
+	if (trc->recs)
+		return;
+
+	memset(trc, 0, sizeof(*trc));
+
+	trc->name = name;
+	spin_lock_init(&trc->trc_lock);
+	if (!num_entries)
+		return;
+	trc->num_entries = num_entries;
+	trc->recs = vzalloc(trc->num_entries *
+				sizeof(struct qla_trace_rec));
+	if (!trc->recs)
+		return;
+
+	set_bit(QLA_TRACE_ENABLED, &trc->flags);
+}
+
+static inline void
+qla_trace_uninit(struct qla_trace *trc)
+{
+	if (!trc->recs)
+		return;
+
+	vfree(trc->recs);
+	trc->recs = NULL;
+	clear_bit(QLA_TRACE_ENABLED, &trc->flags);
+}
+
+#else /* QLA_TRACING */
+#define qla_trace_init(trc, name, num)
+#define qla_trace_uninit(trc)
+#define qla_tracing_init()
+#define qla_tracing_exit()
+#endif /* QLA_TRACING */
+
 void __attribute__((format (printf, 4, 5)))
 ql_dbg(uint, scsi_qla_host_t *vha, uint, const char *fmt, ...);
 void __attribute__((format (printf, 4, 5)))
diff --git a/drivers/scsi/qla2xxx/qla_def.h b/drivers/scsi/qla2xxx/qla_def.h
index 22274b405d01..39322105e7be 100644
--- a/drivers/scsi/qla2xxx/qla_def.h
+++ b/drivers/scsi/qla2xxx/qla_def.h
@@ -35,6 +35,37 @@
 
 #include <uapi/scsi/fc/fc_els.h>
 
+#define QLA_TRACING /* Captures driver messages to buffer */
+
+#ifdef QLA_TRACING
+#define QLA_TRACE_LINE_SIZE		256	/* Biggest so far is ~215 */
+#define qla_trace_ind_norm(_trc, _ind)	((_ind) >= (_trc)->num_entries ? \
+							0 : (_ind))
+#define qla_trace_record(_trc, __ind)	((_trc)->recs[__ind].buf)
+#define qla_trace_record_len		(sizeof(struct qla_trace_rec))
+#define qla_trace_start(_trc)		qla_trace_record(_trc, 0)
+#define qla_trace_len(_trc)		((_trc)->num_entries)
+#define qla_trace_size(_trc)		(qla_trace_record_len * \
+						(_trc)->num_entries)
+#define qla_trace_cur_ind(_trc)		((_trc)->trace_ind)
+struct qla_trace_rec {
+	char buf[QLA_TRACE_LINE_SIZE];
+};
+
+struct qla_trace {
+#define QLA_TRACE_ENABLED	0 /* allow trace writes or not */
+#define QLA_TRACE_WRAPPED	1
+#define QLA_TRACE_QUIESCE	2
+	unsigned long	flags;
+	atomic_t	ref_count;
+	u32		num_entries;
+	u32		trace_ind;
+	spinlock_t	trc_lock;
+	char		*name;
+	struct qla_trace_rec *recs;
+};
+#endif /* QLA_TRACING */
+
 #define QLA_DFS_DEFINE_DENTRY(_debugfs_file_name) \
 	struct dentry *dfs_##_debugfs_file_name
 #define QLA_DFS_ROOT_DEFINE_DENTRY(_debugfs_file_name) \
diff --git a/drivers/scsi/qla2xxx/qla_dfs.c b/drivers/scsi/qla2xxx/qla_dfs.c
index c3c8b9536ef6..98c6390ad1f1 100644
--- a/drivers/scsi/qla2xxx/qla_dfs.c
+++ b/drivers/scsi/qla2xxx/qla_dfs.c
@@ -489,6 +489,108 @@ qla_dfs_naqp_show(struct seq_file *s, void *unused)
 	return 0;
 }
 
+#ifdef QLA_TRACING
+static char *trace_help = "\
+# Format:\n\
+#   <msec> <cpu#> <message>\n\
+#\n\
+# Trace control by writing:\n\
+#   'enable' - to enable this trace\n\
+#   'disable' - to disable this trace\n\
+#   'resize=<nlines>' - to resize this trace to <nlines>\n\
+#\n";
+
+static int
+qla_dfs_trace_show(struct seq_file *s, void *unused)
+{
+	struct qla_trace *trc = s->private;
+	char *buf;
+	u32 t_ind = 0, i;
+
+	seq_puts(s, trace_help);
+
+	if (qla_trace_get(trc))
+		return 0;
+
+	seq_printf(s, "# Trace max lines = %d, writes = %s\n#\n",
+		   trc->num_entries, test_bit(QLA_TRACE_ENABLED,
+		   &trc->flags) ? "enabled" : "disabled");
+
+	if (test_bit(QLA_TRACE_WRAPPED, &trc->flags))
+		t_ind = qla_trace_cur_ind(trc) + 1;
+
+	for (i = 0; i < qla_trace_len(trc); i++, t_ind++) {
+		t_ind = qla_trace_ind_norm(trc, t_ind);
+		buf = qla_trace_record(trc, t_ind);
+		if (!buf[0])
+			continue;
+		seq_puts(s, buf);
+	}
+
+	mb();
+	qla_trace_put(trc);
+	return 0;
+}
+
+#define string_is(_buf, _str_val) \
+	(strncmp(_str_val, _buf, strlen(_str_val)) == 0)
+
+static ssize_t
+qla_dfs_trace_write(struct file *file, const char __user *buffer,
+		    size_t count, loff_t *pos)
+{
+	struct seq_file *s = file->private_data;
+	struct qla_trace *trc = s->private;
+	char buf[32];
+	ssize_t ret = count;
+
+	memset(buf, 0, sizeof(buf));
+	if (copy_from_user(buf, buffer, min(sizeof(buf), count)))
+		return -EFAULT;
+
+	if (string_is(buf, "enable")) {
+		if (!trc->recs) {
+			pr_warn("qla2xxx: '%s' is empty, resize before enabling.\n",
+					trc->name);
+			return -EINVAL;
+		}
+		pr_info("qla2xxx: Enabling trace '%s'\n", trc->name);
+		set_bit(QLA_TRACE_ENABLED, &trc->flags);
+	} else if (string_is(buf, "disable")) {
+		pr_info("qla2xxx: Disabling trace '%s'\n", trc->name);
+		clear_bit(QLA_TRACE_ENABLED, &trc->flags);
+	} else if (string_is(buf, "resize")) {
+		u32 new_len;
+
+		if (sscanf(buf, "resize=%d", &new_len) != 1)
+			return -EINVAL;
+		if (new_len == trc->num_entries) {
+			pr_info("qla2xxx: New trace size is same as old.\n");
+			return count;
+		}
+		pr_info("qla2xxx: Changing trace '%s' size to %d\n",
+			trc->name, new_len);
+		if (qla_trace_quiesce(trc)) {
+			ret = -EBUSY;
+			goto done;
+		}
+		qla_trace_uninit(trc);
+		/*
+		 * Go through init once again to start creating traces
+		 * based on the respective tunable.
+		 */
+		qla_trace_init(trc, trc->name, new_len);
+		if (!trc->recs) {
+			pr_warn("qla2xxx: Trace allocation failed for '%s'\n",
+				trc->name);
+			ret = -ENOMEM;
+		}
+	}
+done:
+	return ret;
+}
+#endif /* QLA_TRACING */
+
 /*
  * Helper macros for setting up debugfs entries.
  * _name: The name of the debugfs entry
diff --git a/drivers/scsi/qla2xxx/qla_os.c b/drivers/scsi/qla2xxx/qla_os.c
index 0bd0fd1042df..0d2397069cac 100644
--- a/drivers/scsi/qla2xxx/qla_os.c
+++ b/drivers/scsi/qla2xxx/qla_os.c
@@ -8191,6 +8191,8 @@ qla2x00_module_init(void)
 	BUILD_BUG_ON(sizeof(sw_info_t) != 32);
 	BUILD_BUG_ON(sizeof(target_id_t) != 2);
 
+	qla_tracing_init();
+
 	/* Allocate cache for SRBs. */
 	srb_cachep = kmem_cache_create("qla2xxx_srbs", sizeof(srb_t), 0,
 	    SLAB_HWCACHE_ALIGN, NULL);
@@ -8269,6 +8271,7 @@ qla2x00_module_init(void)
 
 destroy_cache:
 	kmem_cache_destroy(srb_cachep);
+	qla_tracing_exit();
 	return ret;
 }
 
@@ -8287,6 +8290,8 @@ qla2x00_module_exit(void)
 	fc_release_transport(qla2xxx_transport_template);
 	qlt_exit();
 	kmem_cache_destroy(srb_cachep);
+
+	qla_tracing_exit();
 }
 
 module_init(qla2x00_module_init);
-- 
2.19.0.rc0