[PATCH v2] [mmotm] trace bio queueing trial only when it occurs

[PATCH v2] [mmotm] trace bio queueing trial only when it occurs

[Minchan Kim]

 * Add history that why it is breaked in changelog.

Thanks for careful review, Wu, Li.

== CUT_HERE ==

If BIO is discarded or cross over end of device,
BIO queueing trial doesn't occur.

Actually the trace was called just before make_request at first:
[PATCH] Block queue IO tracing support (blktrace) as of 2006-03-23
      2056a782f8e7e65fd4bfd027506b4ce1c5e9ccd4

And then 2 patches added some checks between them:
[PATCH] md: check bio address after mapping through partitions
        5ddfe9691c91a244e8d1be597b6428fcefd58103,
[BLOCK] Don't allow empty barriers to be passed down to 
queues that don't grok them
        51fd77bd9f512ab6cc9df0733ba1caaab89eb957

It breaks original goal.
Let's trace it only when it happens.

Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
Acked-by: Wu Fengguang <fengguang.wu@intel.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
---
 block/blk-core.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index 5b59592..1a0cfd5 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1463,8 +1463,6 @@ static inline void __generic_make_request(struct bio *bio)
 		if (old_sector != -1)
 			trace_block_remap(q, bio, old_dev, old_sector);

-		trace_block_bio_queue(q, bio);
-
 		old_sector = bio->bi_sector;
 		old_dev = bio->bi_bdev->bd_dev;

@@ -1477,6 +1475,8 @@ static inline void __generic_make_request(struct bio *bio)
 			goto end_io;
 		}

+		trace_block_bio_queue(q, bio);
+
 		ret = q->make_request_fn(q, bio);
 	} while (ret);

--
1.6.4



-- 
Kind regards,
Minchan Kim

Re: [PATCH v2] [mmotm] trace bio queueing trial only when it occurs

[Jens Axboe]

On Tue, Sep 08 2009, Minchan Kim wrote:
> 
>  * Add history that why it is breaked in changelog.
> 
> Thanks for careful review, Wu, Li.

Applied to for-2.6.32.

-- 
Jens Axboe