[PATCH 1/3] block: Add a tracepoint for block request remapping

Jun'ichi Nomura
2009-09-18T15:25:52Z

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: Jens Axboe <jens.axboe@oracle.com>
Cc: Alasdair G Kergon <agk@redhat.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
---
block/blk-core.c | 1 +
include/trace/events/block.h | 33 +++++++++++++++++++++++++++++++++
kernel/trace/blktrace.c | 34 ++++++++++++++++++++++++++++++++++
3 files changed, 68 insertions(+)

Index: linux-2.6.31.work/block/blk-core.c
===================================================================
--- linux-2.6.31.work.orig/block/blk-core.c
+++ linux-2.6.31.work/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);
Index: linux-2.6.31.work/include/trace/events/block.h
===================================================================
--- linux-2.6.31.work.orig/include/trace/events/block.h
+++ linux-2.6.31.work/include/trace/events/block.h
@@ -486,6 +486,39 @@ 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 */
Index: linux-2.6.31.work/kernel/trace/blktrace.c
===================================================================
--- linux-2.6.31.work.orig/kernel/trace/blktrace.c
+++ linux-2.6.31.work/kernel/trace/blktrace.c
@@ -852,6 +852,37 @@ static void blk_add_trace_remap(struct r
}

/**
+ * 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
@@ -918,10 +949,13 @@ static void blk_register_tracepoints(voi
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);