2 files changed, 29 insertions, 6 deletions

diff --git a/include/linux/blktrace_api.h b/include/linux/blktrace_api.h
index 7c2e030e72f1..a12f6ed91c84 100644
--- a/include/linux/blktrace_api.h
+++ b/include/linux/blktrace_api.h
@@ -5,6 +5,7 @@
 #include <linux/relay.h>
 #include <linux/compat.h>
 #include <uapi/linux/blktrace_api.h>
+#include <linux/list.h>
 
 #if defined(CONFIG_BLK_DEV_IO_TRACE)
 
@@ -23,6 +24,7 @@ struct blk_trace {
         struct dentry *dir;
         struct dentry *dropped_file;
         struct dentry *msg_file;
+        struct list_head running_list;
         atomic_t dropped;
 };
 
diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index b8b8560bfb95..7f727b34280d 100644
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -26,6 +26,7 @@
 #include <linux/export.h>
 #include <linux/time.h>
 #include <linux/uaccess.h>
+#include <linux/list.h>
 
 #include <trace/events/block.h>
 
@@ -38,6 +39,9 @@ static unsigned int blktrace_seq __read_mostly = 1;
 static struct trace_array *blk_tr;
 static bool blk_tracer_enabled __read_mostly;
 
+static LIST_HEAD(running_trace_list);
+static __cacheline_aligned_in_smp DEFINE_SPINLOCK(running_trace_lock);
+
 /* Select an alternative, minimalistic output than the original one */
 #define TRACE_BLK_OPT_CLASSIC   0x1
 
@@ -107,10 +111,18 @@ record_it:
  * Send out a notify for this process, if we haven't done so since a trace
  * started
  */
-static void trace_note_tsk(struct blk_trace *bt, struct task_struct *tsk)
+static void trace_note_tsk(struct task_struct *tsk)
 {
+        unsigned long flags;
+        struct blk_trace *bt;
+
         tsk->btrace_seq = blktrace_seq;
-        trace_note(bt, tsk->pid, BLK_TN_PROCESS, tsk->comm, sizeof(tsk->comm));
+        spin_lock_irqsave(&running_trace_lock, flags);
+        list_for_each_entry(bt, &running_trace_list, running_list) {
+                trace_note(bt, tsk->pid, BLK_TN_PROCESS, tsk->comm,
+                           sizeof(tsk->comm));
+        }
+        spin_unlock_irqrestore(&running_trace_lock, flags);
 }
 
 static void trace_note_time(struct blk_trace *bt)
@@ -229,16 +241,15 @@ static void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes,
                 goto record_it;
         }
 
+        if (unlikely(tsk->btrace_seq != blktrace_seq))
+                trace_note_tsk(tsk);
+
         /*
          * 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.
          */
         local_irq_save(flags);
-
-        if (unlikely(tsk->btrace_seq != blktrace_seq))
-                trace_note_tsk(bt, tsk);
-
         t = relay_reserve(bt->rchan, sizeof(*t) + pdu_len);
         if (t) {
                 sequence = per_cpu_ptr(bt->sequence, cpu);
@@ -477,6 +488,7 @@ int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
         bt->dir = dir;
         bt->dev = dev;
         atomic_set(&bt->dropped, 0);
+        INIT_LIST_HEAD(&bt->running_list);
 
         ret = -EIO;
         bt->dropped_file = debugfs_create_file("dropped", 0444, dir, bt,
@@ -601,6 +613,9 @@ int blk_trace_startstop(struct request_queue *q, int start)
                         blktrace_seq++;
                         smp_mb();
                         bt->trace_state = Blktrace_running;
+                        spin_lock_irq(&running_trace_lock);
+                        list_add(&bt->running_list, &running_trace_list);
+                        spin_unlock_irq(&running_trace_lock);
 
                         trace_note_time(bt);
                         ret = 0;
@@ -608,6 +623,9 @@ int blk_trace_startstop(struct request_queue *q, int start)
         } else {
                 if (bt->trace_state == Blktrace_running) {
                         bt->trace_state = Blktrace_stopped;
+                        spin_lock_irq(&running_trace_lock);
+                        list_del_init(&bt->running_list);
+                        spin_unlock_irq(&running_trace_lock);
                         relay_flush(bt->rchan);
                         ret = 0;
                 }
@@ -1472,6 +1490,9 @@ static int blk_trace_remove_queue(struct request_queue *q)
         if (atomic_dec_and_test(&blk_probes_ref))
                 blk_unregister_tracepoints();
 
+        spin_lock_irq(&running_trace_lock);
+        list_del(&bt->running_list);
+        spin_unlock_irq(&running_trace_lock);
         blk_trace_free(bt);
         return 0;
 }