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SubjectRe: [PATCH] block: add missing block_bio_complete() tracepoint

2012-01-30 4:24 AM, Tejun Heo wrote:
> On Sun, Jan 29, 2012 at 06:41:33 PM +0900, Namhyung Kim wrote:
>> The block_bio_complete() TP has been missed so long, so that bio-based
>> drivers haven't been able to trace its IO behavior. Add it.
>> In some rare cases, such as loop_switch, @bio->bi_bdev can be NULL.
>> Thus convert it to TRACE_EVENT_CONDITION() as Steven suggested.
>> From now on, request-based drivers will also get BLK_TA_COMPLETEs for
>> all bio's in requests. This needs to be handled in userland properly.
>> Also remove external use of the TP in DM and unexport it.
>> Signed-off-by: Namhyung Kim <>
>> Cc: Tejun Heo <>
>> Cc: Steven Rostedt <>
>> Cc:
> I like the smiplicity change but do we know how we can filter this out
> from userland? Also, what's the reason not to do it from blktrace.c?
> What would be the downside of doing that?
> Thanks.

The userland tool cannot distinguish bounced bio from original one at
completion TP, but it can expect there will be a duplicated
BLK_TA_COMPLETE as it sees BLK_TA_BOUNCE for the bio before.

Filtering it out from kernel side seems to hide a real information that
(paranoid?) user might want to get, and it looks like providing "polcy
not mechanism" IMHO. That's why I changed my mind finally.

I cannot think of the downside, anyway it's not a big deal, if you think
it's wrong choice, I'm OK to change it again.


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