Add a tracepoint for block request remapping

Since 2.6.31 now has request-based device-mapper, it's useful to have
a tracepoint for request-remapping as well as bio-remapping.
This patch adds a tracepoint for request-remapping, trace_block_rq_remap().

Signed-off-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Cc: Alasdair G Kergon <agk@redhat.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 34 insertions, 0 deletions

diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index 60b5c5a3d4b4..d9d6206e0b14 100644
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -856,6 +856,37 @@ static void blk_add_trace_remap(struct request_queue *q, struct bio *bio,
 }
 
 /**
+ * blk_add_trace_rq_remap - Add a trace for a request-remap operation
+ * @q:          queue the io is for
+ * @rq:         the source request
+ * @dev:        target device
+ * @from:       source sector
+ *
+ * Description:
+ *     Device mapper remaps request to other devices.
+ *     Add a trace for that action.
+ *
+ **/
+static void blk_add_trace_rq_remap(struct request_queue *q,
+                                   struct request *rq, dev_t dev,
+                                   sector_t from)
+{
+        struct blk_trace *bt = q->blk_trace;
+        struct blk_io_trace_remap r;
+
+        if (likely(!bt))
+                return;
+
+        r.device_from = cpu_to_be32(dev);
+        r.device_to   = cpu_to_be32(disk_devt(rq->rq_disk));
+        r.sector_from = cpu_to_be64(from);
+
+        __blk_add_trace(bt, blk_rq_pos(rq), blk_rq_bytes(rq),
+                        rq_data_dir(rq), BLK_TA_REMAP, !!rq->errors,
+                        sizeof(r), &r);
+}
+
+/**
  * blk_add_driver_data - Add binary message with driver-specific data
  * @q:          queue the io is for
  * @rq:         io request
@@ -922,10 +953,13 @@ static void blk_register_tracepoints(void)
         WARN_ON(ret);
         ret = register_trace_block_remap(blk_add_trace_remap);
         WARN_ON(ret);
+        ret = register_trace_block_rq_remap(blk_add_trace_rq_remap);
+        WARN_ON(ret);
 }
 
 static void blk_unregister_tracepoints(void)
 {
+        unregister_trace_block_rq_remap(blk_add_trace_rq_remap);
         unregister_trace_block_remap(blk_add_trace_remap);
         unregister_trace_block_split(blk_add_trace_split);
         unregister_trace_block_unplug_io(blk_add_trace_unplug_io);