Added in user-injected messages into blk traces

This allows a user to annotate the blk trace stream: writing a suitable
message to {/sys/kernel/debug}/block/<dsf>/msg will have it propagated
into the trace stream.

Signed-off-by: Alan D. Brunelle <alan.brunelle@hp.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

2 files changed, 46 insertions, 0 deletions

diff --git a/block/blktrace.c b/block/blktrace.c
index 8d3a27780260..eb9651ccb241 100644
--- a/block/blktrace.c
+++ b/block/blktrace.c
@@ -244,6 +244,7 @@ err:
 static void blk_trace_cleanup(struct blk_trace *bt)
 {
         relay_close(bt->rchan);
+        debugfs_remove(bt->msg_file);
         debugfs_remove(bt->dropped_file);
         blk_remove_tree(bt->dir);
         free_percpu(bt->sequence);
@@ -291,6 +292,44 @@ static const struct file_operations blk_dropped_fops = {
         .read =         blk_dropped_read,
 };
 
+static int blk_msg_open(struct inode *inode, struct file *filp)
+{
+        filp->private_data = inode->i_private;
+
+        return 0;
+}
+
+static ssize_t blk_msg_write(struct file *filp, const char __user *buffer,
+                                size_t count, loff_t *ppos)
+{
+        char *msg;
+        struct blk_trace *bt;
+
+        if (count > BLK_TN_MAX_MSG)
+                return -EINVAL;
+
+        msg = kmalloc(count, GFP_KERNEL);
+        if (msg == NULL)
+                return -ENOMEM;
+
+        if (copy_from_user(msg, buffer, count)) {
+                kfree(msg);
+                return -EFAULT;
+        }
+
+        bt = filp->private_data;
+        __trace_note_message(bt, "%s", msg);
+        kfree(msg);
+
+        return count;
+}
+
+static const struct file_operations blk_msg_fops = {
+        .owner =        THIS_MODULE,
+        .open =         blk_msg_open,
+        .write =        blk_msg_write,
+};
+
 /*
  * Keep track of how many times we encountered a full subbuffer, to aid
  * the user space app in telling how many lost events there were.
@@ -380,6 +419,10 @@ int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
         if (!bt->dropped_file)
                 goto err;
 
+        bt->msg_file = debugfs_create_file("msg", 0222, dir, bt, &blk_msg_fops);
+        if (!bt->msg_file)
+                goto err;
+
         bt->rchan = relay_open("trace", dir, buts->buf_size,
                                 buts->buf_nr, &blk_relay_callbacks, bt);
         if (!bt->rchan)
@@ -409,6 +452,8 @@ err:
         if (dir)
                 blk_remove_tree(dir);
         if (bt) {
+                if (bt->msg_file)
+                        debugfs_remove(bt->msg_file);
                 if (bt->dropped_file)
                         debugfs_remove(bt->dropped_file);
                 free_percpu(bt->sequence);
diff --git a/include/linux/blktrace_api.h b/include/linux/blktrace_api.h
index e3ef903aae88..d084b8d227a5 100644
--- a/include/linux/blktrace_api.h
+++ b/include/linux/blktrace_api.h
@@ -129,6 +129,7 @@ struct blk_trace {
         u32 dev;
         struct dentry *dir;
         struct dentry *dropped_file;
+        struct dentry *msg_file;
         atomic_t dropped;
 };