block: trace bio queueing trial only when it occurs
Minchan Kim [Tue, 8 Sep 2009 19:56:38 +0000 (21:56 +0200)]
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>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

block/blk-core.c

index 93051d1..982d634 100644 (file)
@@ -1462,8 +1462,6 @@ 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;
 
@@ -1476,6 +1474,8 @@ 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);