[PATCH] blktrace: fix to trace a partition, instead of only disk

[Shawn Du <duyuyang@gmail.com>]

I made some changes to block/blktrace.c to make it able to trace a partition as the -d option specified.
Doing so by simply using start_lba and end_lba, these two parameters are not passed in from user space,but figured out by do_blk_trace_setup() in kernel. 

From: Shawn Du <duyuyang@gmail.com>
Date: Wed, 17 Dec 2008 11:57:46 +0800
Subject: [PATCH] Trace a partition
Signed-off-by: Shawn Du <duyuyang@gmail.com>
---
 block/blktrace.c |    9 ++++++---
 1 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/block/blktrace.c b/block/blktrace.c
index 85049a7..b8ea04c 100644
--- a/block/blktrace.c
+++ b/block/blktrace.c
@@ -420,10 +420,13 @@ int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
 	if (!bt->act_mask)
 		bt->act_mask = (u16) -1;
 
-	bt->start_lba = buts->start_lba;
-	bt->end_lba = buts->end_lba;
-	if (!bt->end_lba)
+	if (bdev->bd_part) {
+		bt->start_lba = bdev->bd_part->start_sect;
+		bt->end_lba = bt->start_lba + bdev->bd_part->nr_sects;
+	} else {
+		bt->start_lba = 0;
 		bt->end_lba = -1ULL;
+	}
 
 	bt->pid = buts->pid;
 	bt->trace_state = Blktrace_setup;
-- 
1.5.2.5