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

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 <[email protected]>
Date: Wed, 17 Dec 2008 11:57:46 +0800
Subject: [PATCH] Trace a partition

Signed-off-by Shawn Du <[email protected]>

---
 block/blktrace.c |    9 ++++++---
 1 files changed, 6 insertions(+), 3 deletions(-)

block/blktrace.c +6 -3

index 85049a7..b8ea04c 100644
@@ -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;

Signature · 1 line

1.5.2.5

Very nice! The only problem with this is that we have actions that are, by definition, per device. So we probably want to include any sector that is within the range of the partition, AND a zero sector. So that means changing act_log_check() to something ala:

(quoted diff) +1 -1

-       if (sector < bt->start_lba || sector > bt->end_lba)
+       if (!sector || sector < bt->start_lba || sector > bt->end_lba)
               return 1;

in pseudo patch form.

Quoted 10 lines

Very nice! The only problem with this is that we have actions that are, by definition, per device. So we probably want to include any sector that is within the range of the partition, AND a zero sector. So that means changing act_log_check() to something ala:

(quoted diff) +1 -1

-       if (sector < bt->start_lba || sector > bt->end_lba)
+       if (!sector || sector < bt->start_lba || sector > bt->end_lba)
               return 1;

in pseudo patch form.

Thank you sir. And perhaps, we change in __blk_add_trace():