linux-kernel - Re: [PATCH v2 4/4] lockdep: Assign a lock_class per gendisk used for wait_for

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Date:   Mon, 23 Oct 2017 08:53:35 +0900
From:   Byungchul Park <byungchul.park@....com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     peterz@...radead.org, mingo@...nel.org, tglx@...utronix.de,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org, tj@...nel.org,
        johannes.berg@...el.com, oleg@...hat.com, amir73il@...il.com,
        david@...morbit.com, darrick.wong@...cle.com,
        linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-block@...r.kernel.org, idryomov@...il.com,
        kernel-team@....com
Subject: Re: [PATCH v2 4/4] lockdep: Assign a lock_class per gendisk used for
 wait_for_completion()

On Fri, Oct 20, 2017 at 07:44:51AM -0700, Christoph Hellwig wrote:
> The Subject prefix for this should be "block:".
> 
> > @@ -945,7 +945,7 @@ int submit_bio_wait(struct bio *bio)
> >  {
> >  	struct submit_bio_ret ret;
> >  
> > -	init_completion(&ret.event);
> > +	init_completion_with_map(&ret.event, &bio->bi_disk->lockdep_map);
> 
> FYI, I have an outstanding patch to simplify this a lot, which
> switches this to DECLARE_COMPLETION_ONSTACK.  I can delay this or let
> you pick it up with your series, but we'll need a variant of
> DECLARE_COMPLETION_ONSTACK with the lockdep annotations.

Hello,

I'm sorry for late.

I think your patch makes block code simpler and better. I like it.

But, I just wonder if it's related to my series. Is it proper to add
your patch into my series?

Thanks,
Byungchul

> Patch below for reference:
> 
> ---
> >From d65b89843c9f82c0744643515ba51dd10e66e67b Mon Sep 17 00:00:00 2001
> From: Christoph Hellwig <hch@....de>
> Date: Thu, 5 Oct 2017 18:31:02 +0200
> Subject: block: use DECLARE_COMPLETION_ONSTACK in submit_bio_wait
> 
> Simplify the code by getting rid of the submit_bio_ret structure.
> 
> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
>  block/bio.c | 19 +++++--------------
>  1 file changed, 5 insertions(+), 14 deletions(-)
> 
> diff --git a/block/bio.c b/block/bio.c
> index 8338304ea256..4e18e959fc0a 100644
> --- a/block/bio.c
> +++ b/block/bio.c
> @@ -917,17 +917,9 @@ int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
>  }
>  EXPORT_SYMBOL_GPL(bio_iov_iter_get_pages);
>  
> -struct submit_bio_ret {
> -	struct completion event;
> -	int error;
> -};
> -
>  static void submit_bio_wait_endio(struct bio *bio)
>  {
> -	struct submit_bio_ret *ret = bio->bi_private;
> -
> -	ret->error = blk_status_to_errno(bio->bi_status);
> -	complete(&ret->event);
> +	complete(bio->bi_private);
>  }
>  
>  /**
> @@ -943,16 +935,15 @@ static void submit_bio_wait_endio(struct bio *bio)
>   */
>  int submit_bio_wait(struct bio *bio)
>  {
> -	struct submit_bio_ret ret;
> +	DECLARE_COMPLETION_ONSTACK(done);
>  
> -	init_completion(&ret.event);
> -	bio->bi_private = &ret;
> +	bio->bi_private = &done;
>  	bio->bi_end_io = submit_bio_wait_endio;
>  	bio->bi_opf |= REQ_SYNC;
>  	submit_bio(bio);
> -	wait_for_completion_io(&ret.event);
> +	wait_for_completion_io(&done);
>  
> -	return ret.error;
> +	return blk_status_to_errno(bio->bi_status);
>  }
>  EXPORT_SYMBOL(submit_bio_wait);
>  
> -- 
> 2.14.2