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>

4 files changed, 69 insertions, 1 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index 34504f309728..ddaaea4fdffc 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -34,6 +34,7 @@
 #include "blk.h"
 
 EXPORT_TRACEPOINT_SYMBOL_GPL(block_remap);
+EXPORT_TRACEPOINT_SYMBOL_GPL(block_rq_remap);
 EXPORT_TRACEPOINT_SYMBOL_GPL(block_bio_complete);
 
 static int __make_request(struct request_queue *q, struct bio *bio);
diff --git a/include/linux/blktrace_api.h b/include/linux/blktrace_api.h
index 622939a23299..3b73b9992b26 100644
--- a/include/linux/blktrace_api.h
+++ b/include/linux/blktrace_api.h
@@ -212,7 +212,7 @@ extern struct attribute_group blk_trace_attr_group;
 # define blk_trace_startstop(q, start)                  (-ENOTTY)
 # define blk_trace_remove(q)                            (-ENOTTY)
 # define blk_add_trace_msg(q, fmt, ...)                 do { } while (0)
-# define blk_trace_remove_sysfs(struct device *dev)     do { } while (0)
+# define blk_trace_remove_sysfs(dev)                    do { } while (0)
 static inline int blk_trace_init_sysfs(struct device *dev)
 {
         return 0;
diff --git a/include/trace/events/block.h b/include/trace/events/block.h
index d86af94691c2..00405b5f624a 100644
--- a/include/trace/events/block.h
+++ b/include/trace/events/block.h
@@ -488,6 +488,39 @@ TRACE_EVENT(block_remap,
                   (unsigned long long)__entry->old_sector)
 );
 
+TRACE_EVENT(block_rq_remap,
+
+        TP_PROTO(struct request_queue *q, struct request *rq, dev_t dev,
+                 sector_t from),
+
+        TP_ARGS(q, rq, dev, from),
+
+        TP_STRUCT__entry(
+                __field( dev_t,         dev             )
+                __field( sector_t,      sector          )
+                __field( unsigned int,  nr_sector       )
+                __field( dev_t,         old_dev         )
+                __field( sector_t,      old_sector      )
+                __array( char,          rwbs,   6       )
+        ),
+
+        TP_fast_assign(
+                __entry->dev            = disk_devt(rq->rq_disk);
+                __entry->sector         = blk_rq_pos(rq);
+                __entry->nr_sector      = blk_rq_sectors(rq);
+                __entry->old_dev        = dev;
+                __entry->old_sector     = from;
+                blk_fill_rwbs_rq(__entry->rwbs, rq);
+        ),
+
+        TP_printk("%d,%d %s %llu + %u <- (%d,%d) %llu",
+                  MAJOR(__entry->dev), MINOR(__entry->dev), __entry->rwbs,
+                  (unsigned long long)__entry->sector,
+                  __entry->nr_sector,
+                  MAJOR(__entry->old_dev), MINOR(__entry->old_dev),
+                  (unsigned long long)__entry->old_sector)
+);
+
 #endif /* _TRACE_BLOCK_H */
 
 /* This part must be outside protection */
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);