1 files changed, 25 insertions, 4 deletions

diff --git a/block/blktrace.c b/block/blktrace.c
index b2cbb4e5d767..8d3a27780260 100644
--- a/block/blktrace.c
+++ b/block/blktrace.c
@@ -75,6 +75,24 @@ static void trace_note_time(struct blk_trace *bt)
         local_irq_restore(flags);
 }
 
+void __trace_note_message(struct blk_trace *bt, const char *fmt, ...)
+{
+        int n;
+        va_list args;
+        unsigned long flags;
+        char *buf;
+
+        local_irq_save(flags);
+        buf = per_cpu_ptr(bt->msg_data, smp_processor_id());
+        va_start(args, fmt);
+        n = vscnprintf(buf, BLK_TN_MAX_MSG, fmt, args);
+        va_end(args);
+
+        trace_note(bt, 0, BLK_TN_MESSAGE, buf, n);
+        local_irq_restore(flags);
+}
+EXPORT_SYMBOL_GPL(__trace_note_message);
+
 static int act_log_check(struct blk_trace *bt, u32 what, sector_t sector,
                          pid_t pid)
 {
@@ -141,10 +159,7 @@ void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes,
         /*
          * A word about the locking here - we disable interrupts to reserve
          * some space in the relay per-cpu buffer, to prevent an irq
-         * from coming in and stepping on our toes. Once reserved, it's
-         * enough to get preemption disabled to prevent read of this data
-         * before we are through filling it. get_cpu()/put_cpu() does this
-         * for us
+         * from coming in and stepping on our toes.
          */
         local_irq_save(flags);
 
@@ -232,6 +247,7 @@ static void blk_trace_cleanup(struct blk_trace *bt)
         debugfs_remove(bt->dropped_file);
         blk_remove_tree(bt->dir);
         free_percpu(bt->sequence);
+        free_percpu(bt->msg_data);
         kfree(bt);
 }
 
@@ -346,6 +362,10 @@ int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
         if (!bt->sequence)
                 goto err;
 
+        bt->msg_data = __alloc_percpu(BLK_TN_MAX_MSG);
+        if (!bt->msg_data)
+                goto err;
+
         ret = -ENOENT;
         dir = blk_create_tree(buts->name);
         if (!dir)
@@ -392,6 +412,7 @@ err:
                 if (bt->dropped_file)
                         debugfs_remove(bt->dropped_file);
                 free_percpu(bt->sequence);
+                free_percpu(bt->msg_data);
                 if (bt->rchan)
                         relay_close(bt->rchan);
                 kfree(bt);