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Re: [dm-devel] [PATCH] block: add missing block_bio_complete() tracepoint

2012-01-30 11:30 AM, Tejun Heo wrote:
On Mon, Jan 30, 2012 at 11:22:29AM +0900, Namhyung Kim wrote:
It's just that this patch as it stands will break the existing tools
and is likely to cause some amount of head scratching for blktrace
users upgrading to new kernel with existing userland, so yeah, I think
it should be filtered in kernel from blktrace.c.

Will it break blktrace? Looking at the code, not tested though, it
will just add one more 'C' line for bounced bio, and that's it? The
blktrace will get way more 'C' lines for normal request based
devices and it needs to be handled anyway. Am I missing something?

Hmmm... maybe I'm confused.  Wouldn't it cause duplicate completions
for all rq based drivers too?

Yes, blktrace will see both of completions for rq and bio's it contains from now on, and I thought it's your intention? For the bounced bio's, it'll see one more completion per bio.

The users of older blktrace might get confused by this, thus changing the tool is inevitable regardless of the bounced bio's.


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