linux-kernel - Re: [PATCH 2/2] block: remove support for bio remapping from ->make

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Date:	Mon, 12 Sep 2011 05:25:08 +0200
From:	NeilBrown <neilb@...e.de>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	Jens Axboe <axboe@...nel.dk>, linux-raid@...r.kernel.org,
	dm-devel@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] block: remove support for bio remapping from
 ->make_request

On Sun, 11 Sep 2011 10:51:29 -0400 Christoph Hellwig <hch@...radead.org>
wrote:

> There is very little benefit in allowing to let a ->make_request instance update
> the bios device and sector and loop around it in __generic_make_request when
> we can archive the same through calling generic_make_request from the driver
> and letting the loop in generic_make_request handle it.

Completely agree - I like this change!

> 
> Note that various drivers got the return value from ->make_request and returned
> non-zero values for errors.

:-(

A diff-stat would have been nice... I think I've found all 'my' files though.



> Index: linux-2.6/drivers/md/faulty.c
> ===================================================================
> --- linux-2.6.orig/drivers/md/faulty.c	2011-09-08 12:01:53.000000000 +0200
> +++ linux-2.6/drivers/md/faulty.c	2011-09-08 12:05:58.602773802 +0200
> @@ -169,7 +169,7 @@ static void add_sector(conf_t *conf, sec
>  		conf->nfaults = n+1;
>  }
>  
> -static int make_request(mddev_t *mddev, struct bio *bio)
> +static void make_request(mddev_t *mddev, struct bio *bio)
>  {
>  	conf_t *conf = mddev->private;
>  	int failit = 0;
> @@ -181,7 +181,7 @@ static int make_request(mddev_t *mddev,
>  			 * just fail immediately
>  			 */
>  			bio_endio(bio, -EIO);
> -			return 0;
> +			return;
>  		}
>  
>  		if (check_sector(conf, bio->bi_sector, bio->bi_sector+(bio->bi_size>>9),
> @@ -214,12 +214,11 @@ static int make_request(mddev_t *mddev,
>  		b->bi_bdev = conf->rdev->bdev;
>  		b->bi_private = bio;
>  		b->bi_end_io = faulty_fail;
> -		generic_make_request(b);
> -		return 0;
>  	} else {
>  		bio->bi_bdev = conf->rdev->bdev;
> -		return 1;
>  	}
> +
> +	generic_make_request(b);
>  }

If the 'else' branch was taken, we need to generic_make_request(bio).
And 'b' isn't even declared at this level.
So at the end of the 'then' branch, add
        bio = b;
and make the final call
        generic_make_request(bio);


Changes to these files:
> Index: linux-2.6/drivers/md/linear.c
> Index: linux-2.6/drivers/md/multipath.c
> Index: linux-2.6/drivers/md/raid0.c
> Index: linux-2.6/drivers/md/raid1.c
> Index: linux-2.6/drivers/md/raid10.c
> Index: linux-2.6/drivers/md/raid5.c
> Index: linux-2.6/drivers/md/md.h
> Index: linux-2.6/drivers/md/md.c

Acked-by: NeilBrown <neilb@...e.de>

Thanks,
NeilBrown
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