[PATCH -for-next 1/2] block: introduce BIO_IN_FLIGHT flag

[PATCH -for-next 1/2] block: introduce BIO_IN_FLIGHT flag

[Namhyung Kim]

BIO_IN_FLIGHT flag is used for tracing block I/O completion.
This patch fixes tracing bio-based devices - except DM which
inserts completion tracepoint explicitly - that could not be
traced such event using blktrace.

It won't affect tracing normal (request-based) disk devices
and nested bio handling paths.

Signed-off-by: Namhyung Kim <namhyung@gmail.com>
---
 block/blk-core.c          |    5 +++++
 fs/bio.c                  |    9 +++++++++
 include/linux/blk_types.h |    1 +
 3 files changed, 15 insertions(+), 0 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index a99514191ce2..d8005ffc480d 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -162,6 +162,9 @@ static void req_bio_endio(struct request *rq, struct bio *bio,
 	if (unlikely(rq->cmd_flags & REQ_QUIET))
 		set_bit(BIO_QUIET, &bio->bi_flags);
 
+	/* completion event was already reported in blk_update_request */
+	clear_bit(BIO_IN_FLIGHT, &bio->bi_flags);
+
 	bio->bi_size -= nbytes;
 	bio->bi_sector += (nbytes >> 9);
 
@@ -1571,6 +1574,8 @@ void generic_make_request(struct bio *bio)
 	do {
 		struct request_queue *q = bdev_get_queue(bio->bi_bdev);
 
+		set_bit(BIO_IN_FLIGHT, &bio->bi_flags);
+
 		q->make_request_fn(q, bio);
 
 		bio = bio_list_pop(current->bio_list);
diff --git a/fs/bio.c b/fs/bio.c
index 9bfade8a609b..c510e93b6312 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -1447,6 +1447,15 @@ void bio_endio(struct bio *bio, int error)
 	else if (!test_bit(BIO_UPTODATE, &bio->bi_flags))
 		error = -EIO;
 
+	if (test_bit(BIO_IN_FLIGHT, &bio->bi_flags)) {
+		struct request_queue *q = bdev_get_queue(bio->bi_bdev);
+
+		trace_block_bio_complete(q, bio, error);
+
+		/* prevent duplicated completion event report */
+		clear_bit(BIO_IN_FLIGHT, &bio->bi_flags);
+	}
+
 	if (bio->bi_end_io)
 		bio->bi_end_io(bio, error);
 }
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 71fc53bb8f1c..146295babc98 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -98,6 +98,7 @@ struct bio {
 #define BIO_FS_INTEGRITY 10	/* fs owns integrity data, not block layer */
 #define BIO_QUIET	11	/* Make BIO Quiet */
 #define BIO_MAPPED_INTEGRITY 12/* integrity metadata has been remapped */
+#define BIO_IN_FLIGHT	13	/* report I/O completion event */
 #define bio_flagged(bio, flag)	((bio)->bi_flags & (1 << (flag)))
 
 /*
-- 
1.7.6

[PATCH 2/2] block: don't export block_bio_complete tracepoint

[Namhyung Kim]

Now bio_endio() contains the tracepoint in it, so we don't
need to have it twice in DM. Plus, as the only external user
of the tracepoint was the DM, we can unexport the symbol.

Signed-off-by: Namhyung Kim <namhyung@gmail.com>
Cc: dm-devel@redhat.com
---
 block/blk-core.c |    1 -
 drivers/md/dm.c  |    1 -
 2 files changed, 0 insertions(+), 2 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index d8005ffc480d..5c81ef057e6a 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -36,7 +36,6 @@
 
 EXPORT_TRACEPOINT_SYMBOL_GPL(block_bio_remap);
 EXPORT_TRACEPOINT_SYMBOL_GPL(block_rq_remap);
-EXPORT_TRACEPOINT_SYMBOL_GPL(block_bio_complete);
 
 /*
  * For the allocated request tables
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 7b986e77b75e..a8223d92a52b 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -636,7 +636,6 @@ static void dec_pending(struct dm_io *io, int error)
 			queue_io(md, bio);
 		} else {
 			/* done with normal IO or empty flush */
-			trace_block_bio_complete(md->queue, bio, io_error);
 			bio_endio(bio, io_error);
 		}
 	}
-- 
1.7.6