[SCSI] fnic: Fnic Trace Utility

Fnic Trace utility is a tracing functionality built directly into fnic driver
to trace events. The benefit that trace buffer brings to fnic driver is the
ability to see what it happening inside the fnic driver. It also provides the
capability to trace every IO event inside fnic driver to debug panics, hangs
and potentially IO corruption issues. This feature makes it easy to find
problems in fnic driver and it also helps in tracking down strange bugs in a
more manageable way. Trace buffer is shared across all fnic instances for
this implementation.

Signed-off-by: Hiral Patel <hiralpat@cisco.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

1 files changed, 273 insertions, 0 deletions

diff --git a/drivers/scsi/fnic/fnic_trace.c b/drivers/scsi/fnic/fnic_trace.c
new file mode 100644
index 000000000000..23a60e3d8527
--- /dev/null
+++ b/drivers/scsi/fnic/fnic_trace.c
@@ -0,0 +1,273 @@
+/*
+ * Copyright 2012 Cisco Systems, Inc.  All rights reserved.
+ *
+ * This program is free software; you may redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include <linux/module.h>
+#include <linux/mempool.h>
+#include <linux/errno.h>
+#include <linux/spinlock.h>
+#include <linux/kallsyms.h>
+#include "fnic_io.h"
+#include "fnic.h"
+
+unsigned int trace_max_pages;
+static int fnic_max_trace_entries;
+
+static unsigned long fnic_trace_buf_p;
+static DEFINE_SPINLOCK(fnic_trace_lock);
+
+static fnic_trace_dbg_t fnic_trace_entries;
+int fnic_tracing_enabled = 1;
+
+/*
+ * fnic_trace_get_buf - Give buffer pointer to user to fill up trace information
+ *
+ * Description:
+ * This routine gets next available trace buffer entry location @wr_idx
+ * from allocated trace buffer pages and give that memory location
+ * to user to store the trace information.
+ *
+ * Return Value:
+ * This routine returns pointer to next available trace entry
+ * @fnic_buf_head for user to fill trace information.
+ */
+fnic_trace_data_t *fnic_trace_get_buf(void)
+{
+	unsigned long fnic_buf_head;
+	unsigned long flags;
+
+	spin_lock_irqsave(&fnic_trace_lock, flags);
+
+	/*
+	 * Get next available memory location for writing trace information
+	 * at @wr_idx and increment @wr_idx
+	 */
+	fnic_buf_head =
+		fnic_trace_entries.page_offset[fnic_trace_entries.wr_idx];
+	fnic_trace_entries.wr_idx++;
+
+	/*
+	 * Verify if trace buffer is full then change wd_idx to
+	 * start from zero
+	 */
+	if (fnic_trace_entries.wr_idx >= fnic_max_trace_entries)
+		fnic_trace_entries.wr_idx = 0;
+
+	/*
+	 * Verify if write index @wr_idx and read index @rd_idx are same then
+	 * increment @rd_idx to move to next entry in trace buffer
+	 */
+	if (fnic_trace_entries.wr_idx == fnic_trace_entries.rd_idx) {
+		fnic_trace_entries.rd_idx++;
+		if (fnic_trace_entries.rd_idx >= fnic_max_trace_entries)
+			fnic_trace_entries.rd_idx = 0;
+	}
+	spin_unlock_irqrestore(&fnic_trace_lock, flags);
+	return (fnic_trace_data_t *)fnic_buf_head;
+}
+
+/*
+ * fnic_get_trace_data - Copy trace buffer to a memory file
+ * @fnic_dbgfs_t: pointer to debugfs trace buffer
+ *
+ * Description:
+ * This routine gathers the fnic trace debugfs data from the fnic_trace_data_t
+ * buffer and dumps it to fnic_dbgfs_t. It will start at the rd_idx entry in
+ * the log and process the log until the end of the buffer. Then it will gather
+ * from the beginning of the log and process until the current entry @wr_idx.
+ *
+ * Return Value:
+ * This routine returns the amount of bytes that were dumped into fnic_dbgfs_t
+ */
+int fnic_get_trace_data(fnic_dbgfs_t *fnic_dbgfs_prt)
+{
+	int rd_idx;
+	int wr_idx;
+	int len = 0;
+	unsigned long flags;
+	char str[KSYM_SYMBOL_LEN];
+	struct timespec val;
+	fnic_trace_data_t *tbp;
+
+	spin_lock_irqsave(&fnic_trace_lock, flags);
+	rd_idx = fnic_trace_entries.rd_idx;
+	wr_idx = fnic_trace_entries.wr_idx;
+	if (wr_idx < rd_idx) {
+		while (1) {
+			/* Start from read index @rd_idx */
+			tbp = (fnic_trace_data_t *)
+				  fnic_trace_entries.page_offset[rd_idx];
+			if (!tbp) {
+				spin_unlock_irqrestore(&fnic_trace_lock, flags);
+				return 0;
+			}
+			/* Convert function pointer to function name */
+			if (sizeof(unsigned long) < 8) {
+				sprint_symbol(str, tbp->fnaddr.low);
+				jiffies_to_timespec(tbp->timestamp.low, &val);
+			} else {
+				sprint_symbol(str, tbp->fnaddr.val);
+				jiffies_to_timespec(tbp->timestamp.val, &val);
+			}
+			/*
+			 * Dump trace buffer entry to memory file
+			 * and increment read index @rd_idx
+			 */
+			len += snprintf(fnic_dbgfs_prt->buffer + len,
+				  (trace_max_pages * PAGE_SIZE * 3) - len,
+				  "%16lu.%16lu %-50s %8x %8x %16llx %16llx "
+				  "%16llx %16llx %16llx\n", val.tv_sec,
+				  val.tv_nsec, str, tbp->host_no, tbp->tag,
+				  tbp->data[0], tbp->data[1], tbp->data[2],
+				  tbp->data[3], tbp->data[4]);
+			rd_idx++;
+			/*
+			 * If rd_idx is reached to maximum trace entries
+			 * then move rd_idx to zero
+			 */
+			if (rd_idx > (fnic_max_trace_entries-1))
+				rd_idx = 0;
+			/*
+			 * Continure dumpping trace buffer entries into
+			 * memory file till rd_idx reaches write index
+			 */
+			if (rd_idx == wr_idx)
+				break;
+		}
+	} else if (wr_idx > rd_idx) {
+		while (1) {
+			/* Start from read index @rd_idx */
+			tbp = (fnic_trace_data_t *)
+				  fnic_trace_entries.page_offset[rd_idx];
+			if (!tbp) {
+				spin_unlock_irqrestore(&fnic_trace_lock, flags);
+				return 0;
+			}
+			/* Convert function pointer to function name */
+			if (sizeof(unsigned long) < 8) {
+				sprint_symbol(str, tbp->fnaddr.low);
+				jiffies_to_timespec(tbp->timestamp.low, &val);
+			} else {
+				sprint_symbol(str, tbp->fnaddr.val);
+				jiffies_to_timespec(tbp->timestamp.val, &val);
+			}
+			/*
+			 * Dump trace buffer entry to memory file
+			 * and increment read index @rd_idx
+			 */
+			len += snprintf(fnic_dbgfs_prt->buffer + len,
+				  (trace_max_pages * PAGE_SIZE * 3) - len,
+				  "%16lu.%16lu %-50s %8x %8x %16llx %16llx "
+				  "%16llx %16llx %16llx\n", val.tv_sec,
+				  val.tv_nsec, str, tbp->host_no, tbp->tag,
+				  tbp->data[0], tbp->data[1], tbp->data[2],
+				  tbp->data[3], tbp->data[4]);
+			rd_idx++;
+			/*
+			 * Continue dumpping trace buffer entries into
+			 * memory file till rd_idx reaches write index
+			 */
+			if (rd_idx == wr_idx)
+				break;
+		}
+	}
+	spin_unlock_irqrestore(&fnic_trace_lock, flags);
+	return len;
+}
+
+/*
+ * fnic_trace_buf_init - Initialize fnic trace buffer logging facility
+ *
+ * Description:
+ * Initialize trace buffer data structure by allocating required memory and
+ * setting page_offset information for every trace entry by adding trace entry
+ * length to previous page_offset value.
+ */
+int fnic_trace_buf_init(void)
+{
+	unsigned long fnic_buf_head;
+	int i;
+	int err = 0;
+
+	trace_max_pages = fnic_trace_max_pages;
+	fnic_max_trace_entries = (trace_max_pages * PAGE_SIZE)/
+					  FNIC_ENTRY_SIZE_BYTES;
+
+	fnic_trace_buf_p = (unsigned long)vmalloc((trace_max_pages * PAGE_SIZE));
+	if (!fnic_trace_buf_p) {
+		printk(KERN_ERR PFX "Failed to allocate memory "
+				  "for fnic_trace_buf_p\n");
+		err = -ENOMEM;
+		goto err_fnic_trace_buf_init;
+	}
+	memset((void *)fnic_trace_buf_p, 0, (trace_max_pages * PAGE_SIZE));
+
+	fnic_trace_entries.page_offset = vmalloc(fnic_max_trace_entries *
+						  sizeof(unsigned long));
+	if (!fnic_trace_entries.page_offset) {
+		printk(KERN_ERR PFX "Failed to allocate memory for"
+				  " page_offset\n");
+		if (fnic_trace_buf_p) {
+			vfree((void *)fnic_trace_buf_p);
+			fnic_trace_buf_p = 0;
+		}
+		err = -ENOMEM;
+		goto err_fnic_trace_buf_init;
+	}
+	memset((void *)fnic_trace_entries.page_offset, 0,
+		  (fnic_max_trace_entries * sizeof(unsigned long)));
+	fnic_trace_entries.wr_idx = fnic_trace_entries.rd_idx = 0;
+	fnic_buf_head = fnic_trace_buf_p;
+
+	/*
+	 * Set page_offset field of fnic_trace_entries struct by
+	 * calculating memory location for every trace entry using
+	 * length of each trace entry
+	 */
+	for (i = 0; i < fnic_max_trace_entries; i++) {
+		fnic_trace_entries.page_offset[i] = fnic_buf_head;
+		fnic_buf_head += FNIC_ENTRY_SIZE_BYTES;
+	}
+	err = fnic_trace_debugfs_init();
+	if (err < 0) {
+		printk(KERN_ERR PFX "Failed to initialize debugfs for tracing\n");
+		goto err_fnic_trace_debugfs_init;
+	}
+	printk(KERN_INFO PFX "Successfully Initialized Trace Buffer\n");
+	return err;
+err_fnic_trace_debugfs_init:
+	fnic_trace_free();
+err_fnic_trace_buf_init:
+	return err;
+}
+
+/*
+ * fnic_trace_free - Free memory of fnic trace data structures.
+ */
+void fnic_trace_free(void)
+{
+	fnic_tracing_enabled = 0;
+	fnic_trace_debugfs_terminate();
+	if (fnic_trace_entries.page_offset) {
+		vfree((void *)fnic_trace_entries.page_offset);
+		fnic_trace_entries.page_offset = NULL;
+	}
+	if (fnic_trace_buf_p) {
+		vfree((void *)fnic_trace_buf_p);
+		fnic_trace_buf_p = 0;
+	}
+	printk(KERN_INFO PFX "Successfully Freed Trace Buffer\n");
+}