From: NeilBrown <neilb@suse.com>
To: Christoph Hellwig <hch@infradead.org>
Date: Thu, 23 Mar 2017 17:26:11 +1100
Cc: Jens Axboe <axboe@kernel.dk>, linux-block@vger.kernel.org,
        linux-raid@vger.kernel.org, dm-devel@redhat.com,
        Alasdair Kergon <agk@redhat.com>, Mike Snitzer <snitzer@redhat.com>,
        Shaohua Li <shli@kernel.org>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] block: trace completion of all bios.
In-Reply-To: <20170322125149.GA29606@infradead.org>
References: <877f3iave6.fsf@notabene.neil.brown.name> <20170322125149.GA29606@infradead.org>
Message-ID: <87var0a4qk.fsf@notabene.neil.brown.name>
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On Wed, Mar 22 2017, Christoph Hellwig wrote:

> On Wed, Mar 22, 2017 at 01:38:09PM +1100, NeilBrown wrote:
>>=20
>> Currently only dm and md/raid5 bios trigger trace_block_bio_complete().
>> Now that we have bio_chain(), it is not possible, in general, for a
>> driver to know when the bio is really complete.  Only bio_endio()
>> knows that.
>>=20
>> So move the trace_block_bio_complete() call to bio_endio().
>
> This will cause duplicate events for request based drivers.  You'll
> need to have a bio_endio_notrace or similar without that the request
> completion path can call.

Ah... I hadn't noticed that the request completion was the same event
type as the bio completion...  Thanks.  Also after being processed by the
request handler, bi_sector and bi_size have changed so the trace
messsage would be wrong.

I've sorted that out and will repost.

Thanks,
NeilBrown


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