[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, 314 insertions, 0 deletions

diff --git a/drivers/scsi/fnic/fnic_debugfs.c b/drivers/scsi/fnic/fnic_debugfs.c
new file mode 100644
index 000000000000..adc1f7f471f5
--- /dev/null
+++ b/drivers/scsi/fnic/fnic_debugfs.c
@@ -0,0 +1,314 @@
+/*
+ * 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/errno.h>
+#include <linux/debugfs.h>
+#include "fnic.h"
+
+static struct dentry *fnic_trace_debugfs_root;
+static struct dentry *fnic_trace_debugfs_file;
+static struct dentry *fnic_trace_enable;
+
+/*
+ * fnic_trace_ctrl_open - Open the trace_enable file
+ * @inode: The inode pointer.
+ * @file: The file pointer to attach the trace enable/disable flag.
+ *
+ * Description:
+ * This routine opens a debugsfs file trace_enable.
+ *
+ * Returns:
+ * This function returns zero if successful.
+ */
+static int fnic_trace_ctrl_open(struct inode *inode, struct file *filp)
+{
+	filp->private_data = inode->i_private;
+	return 0;
+}
+
+/*
+ * fnic_trace_ctrl_read - Read a trace_enable debugfs file
+ * @filp: The file pointer to read from.
+ * @ubuf: The buffer to copy the data to.
+ * @cnt: The number of bytes to read.
+ * @ppos: The position in the file to start reading from.
+ *
+ * Description:
+ * This routine reads value of variable fnic_tracing_enabled
+ * and stores into local @buf. It will start reading file at @ppos and
+ * copy up to @cnt of data to @ubuf from @buf.
+ *
+ * Returns:
+ * This function returns the amount of data that was read.
+ */
+static ssize_t fnic_trace_ctrl_read(struct file *filp,
+				  char __user *ubuf,
+				  size_t cnt, loff_t *ppos)
+{
+	char buf[64];
+	int len;
+	len = sprintf(buf, "%u\n", fnic_tracing_enabled);
+
+	return simple_read_from_buffer(ubuf, cnt, ppos, buf, len);
+}
+
+/*
+ * fnic_trace_ctrl_write - Write to trace_enable debugfs file
+ * @filp: The file pointer to write from.
+ * @ubuf: The buffer to copy the data from.
+ * @cnt: The number of bytes to write.
+ * @ppos: The position in the file to start writing to.
+ *
+ * Description:
+ * This routine writes data from user buffer @ubuf to buffer @buf and
+ * sets fnic_tracing_enabled value as per user input.
+ *
+ * Returns:
+ * This function returns the amount of data that was written.
+ */
+static ssize_t fnic_trace_ctrl_write(struct file *filp,
+				  const char __user *ubuf,
+				  size_t cnt, loff_t *ppos)
+{
+	char buf[64];
+	unsigned long val;
+	int ret;
+
+	if (cnt >= sizeof(buf))
+		return -EINVAL;
+
+	if (copy_from_user(&buf, ubuf, cnt))
+		return -EFAULT;
+
+	buf[cnt] = 0;
+
+	ret = kstrtoul(buf, 10, &val);
+	if (ret < 0)
+		return ret;
+
+	fnic_tracing_enabled = val;
+	(*ppos)++;
+
+	return cnt;
+}
+
+/*
+ * fnic_trace_debugfs_open - Open the fnic trace log
+ * @inode: The inode pointer
+ * @file: The file pointer to attach the log output
+ *
+ * Description:
+ * This routine is the entry point for the debugfs open file operation.
+ * It allocates the necessary buffer for the log, fills the buffer from
+ * the in-memory log and then returns a pointer to that log in
+ * the private_data field in @file.
+ *
+ * Returns:
+ * This function returns zero if successful. On error it will return
+ * a negative error value.
+ */
+static int fnic_trace_debugfs_open(struct inode *inode,
+				  struct file *file)
+{
+	fnic_dbgfs_t *fnic_dbg_prt;
+	fnic_dbg_prt = kzalloc(sizeof(fnic_dbgfs_t), GFP_KERNEL);
+	if (!fnic_dbg_prt)
+		return -ENOMEM;
+
+	fnic_dbg_prt->buffer = vmalloc((3*(trace_max_pages * PAGE_SIZE)));
+	if (!fnic_dbg_prt->buffer) {
+		kfree(fnic_dbg_prt);
+		return -ENOMEM;
+	}
+	memset((void *)fnic_dbg_prt->buffer, 0,
+			  (3*(trace_max_pages * PAGE_SIZE)));
+	fnic_dbg_prt->buffer_len = fnic_get_trace_data(fnic_dbg_prt);
+	file->private_data = fnic_dbg_prt;
+	return 0;
+}
+
+/*
+ * fnic_trace_debugfs_lseek - Seek through a debugfs file
+ * @file: The file pointer to seek through.
+ * @offset: The offset to seek to or the amount to seek by.
+ * @howto: Indicates how to seek.
+ *
+ * Description:
+ * This routine is the entry point for the debugfs lseek file operation.
+ * The @howto parameter indicates whether @offset is the offset to directly
+ * seek to, or if it is a value to seek forward or reverse by. This function
+ * figures out what the new offset of the debugfs file will be and assigns
+ * that value to the f_pos field of @file.
+ *
+ * Returns:
+ * This function returns the new offset if successful and returns a negative
+ * error if unable to process the seek.
+ */
+static loff_t fnic_trace_debugfs_lseek(struct file *file,
+					loff_t offset,
+					int howto)
+{
+	fnic_dbgfs_t *fnic_dbg_prt = file->private_data;
+	loff_t pos = -1;
+
+	switch (howto) {
+	case 0:
+		pos = offset;
+		break;
+	case 1:
+		pos = file->f_pos + offset;
+		break;
+	case 2:
+		pos = fnic_dbg_prt->buffer_len - offset;
+	}
+	return (pos < 0 || pos > fnic_dbg_prt->buffer_len) ?
+			  -EINVAL : (file->f_pos = pos);
+}
+
+/*
+ * fnic_trace_debugfs_read - Read a debugfs file
+ * @file: The file pointer to read from.
+ * @ubuf: The buffer to copy the data to.
+ * @nbytes: The number of bytes to read.
+ * @pos: The position in the file to start reading from.
+ *
+ * Description:
+ * This routine reads data from the buffer indicated in the private_data
+ * field of @file. It will start reading at @pos and copy up to @nbytes of
+ * data to @ubuf.
+ *
+ * Returns:
+ * This function returns the amount of data that was read (this could be
+ * less than @nbytes if the end of the file was reached).
+ */
+static ssize_t fnic_trace_debugfs_read(struct file *file,
+					char __user *ubuf,
+					size_t nbytes,
+					loff_t *pos)
+{
+	fnic_dbgfs_t *fnic_dbg_prt = file->private_data;
+	int rc = 0;
+	rc = simple_read_from_buffer(ubuf, nbytes, pos,
+				  fnic_dbg_prt->buffer,
+				  fnic_dbg_prt->buffer_len);
+	return rc;
+}
+
+/*
+ * fnic_trace_debugfs_release - Release the buffer used to store
+ * debugfs file data
+ * @inode: The inode pointer
+ * @file: The file pointer that contains the buffer to release
+ *
+ * Description:
+ * This routine frees the buffer that was allocated when the debugfs
+ * file was opened.
+ *
+ * Returns:
+ * This function returns zero.
+ */
+static int fnic_trace_debugfs_release(struct inode *inode,
+					  struct file *file)
+{
+	fnic_dbgfs_t *fnic_dbg_prt = file->private_data;
+
+	vfree(fnic_dbg_prt->buffer);
+	kfree(fnic_dbg_prt);
+	return 0;
+}
+
+static const struct file_operations fnic_trace_ctrl_fops = {
+	.owner = THIS_MODULE,
+	.open = fnic_trace_ctrl_open,
+	.read = fnic_trace_ctrl_read,
+	.write = fnic_trace_ctrl_write,
+};
+
+static const struct file_operations fnic_trace_debugfs_fops = {
+	.owner = THIS_MODULE,
+	.open = fnic_trace_debugfs_open,
+	.llseek = fnic_trace_debugfs_lseek,
+	.read = fnic_trace_debugfs_read,
+	.release = fnic_trace_debugfs_release,
+};
+
+/*
+ * fnic_trace_debugfs_init - Initialize debugfs for fnic trace logging
+ *
+ * Description:
+ * When Debugfs is configured this routine sets up the fnic debugfs
+ * file system. If not already created, this routine will create the
+ * fnic directory. It will create file trace to log fnic trace buffer
+ * output into debugfs and it will also create file trace_enable to
+ * control enable/disable of trace logging into trace buffer.
+ */
+int fnic_trace_debugfs_init(void)
+{
+	int rc = -1;
+	fnic_trace_debugfs_root = debugfs_create_dir("fnic", NULL);
+	if (!fnic_trace_debugfs_root) {
+		printk(KERN_DEBUG "Cannot create debugfs root\n");
+		return rc;
+	}
+	fnic_trace_enable = debugfs_create_file("tracing_enable",
+					  S_IFREG|S_IRUGO|S_IWUSR,
+					  fnic_trace_debugfs_root,
+					  NULL, &fnic_trace_ctrl_fops);
+
+	if (!fnic_trace_enable) {
+		printk(KERN_DEBUG "Cannot create trace_enable file"
+				  " under debugfs");
+		return rc;
+	}
+
+	fnic_trace_debugfs_file = debugfs_create_file("trace",
+						  S_IFREG|S_IRUGO|S_IWUSR,
+						  fnic_trace_debugfs_root,
+						  NULL,
+						  &fnic_trace_debugfs_fops);
+
+	if (!fnic_trace_debugfs_file) {
+		printk(KERN_DEBUG "Cannot create trace file under debugfs");
+		return rc;
+	}
+	rc = 0;
+	return rc;
+}
+
+/*
+ * fnic_trace_debugfs_terminate - Tear down debugfs infrastructure
+ *
+ * Description:
+ * When Debugfs is configured this routine removes debugfs file system
+ * elements that are specific to fnic trace logging.
+ */
+void fnic_trace_debugfs_terminate(void)
+{
+	if (fnic_trace_debugfs_file) {
+		debugfs_remove(fnic_trace_debugfs_file);
+		fnic_trace_debugfs_file = NULL;
+	}
+	if (fnic_trace_enable) {
+		debugfs_remove(fnic_trace_enable);
+		fnic_trace_enable = NULL;
+	}
+	if (fnic_trace_debugfs_root) {
+		debugfs_remove(fnic_trace_debugfs_root);
+		fnic_trace_debugfs_root = NULL;
+	}
+}