linux-kernel - Re: [patch] direct-io: propagate -ENOSPC errors

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Date:	Wed, 16 Mar 2016 14:25:21 +0100
From:	Carlos Maiolino <cmaiolino@...hat.com>
To:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [patch] direct-io: propagate -ENOSPC errors

This looks good to me.

Reviewed-by: Carlos Maiolino <cmaiolino@...hat.com>

On Mon, Mar 14, 2016 at 05:10:00PM -0400, Jeff Moyer wrote:
> dio_bio_complete turns all errors into -EIO.  This is historical,
> since you used to only get 1 bit precision for errors (BIO_UPTODATE).
> Now that we get actual error codes, we can return the appropriate
> code to userspace.  File systems seem to only propagate either EIO
> or ENOSPC, so I've followed suit in this patch.
> 
> This fixes an issue where -ENOSPC was being turned into -EIO when
> testing dm-thin.
> 
> Reported-by: Carlos Maiolino <cmaiolin@...hat.com>
> Tested-by: Mike Snitzer <snitzer@...hat.com>
> Signed-off-by: Jeff Moyer <jmoyer@...hat.com>
> 
> diff --git a/fs/direct-io.c b/fs/direct-io.c
> index d6a9012..990e0aa 100644
> --- a/fs/direct-io.c
> +++ b/fs/direct-io.c
> @@ -466,13 +466,15 @@ static int dio_bio_complete(struct dio *dio, struct bio *bio)
>  {
>  	struct bio_vec *bvec;
>  	unsigned i;
> -	int err;
>  
> -	if (bio->bi_error)
> +	/* Only EIO and ENOSPC should be returned to userspace. */
> +	if (bio->bi_error == 0 ||
> +	    bio->bi_error == -ENOSPC || bio->bi_error == -EIO)
> +		dio->io_error = bio->bi_error;
> +	else
>  		dio->io_error = -EIO;
>  
>  	if (dio->is_async && dio->rw == READ && dio->should_dirty) {
> -		err = bio->bi_error;
>  		bio_check_pages_dirty(bio);	/* transfers ownership */
>  	} else {
>  		bio_for_each_segment_all(bvec, bio, i) {
> @@ -483,10 +485,9 @@ static int dio_bio_complete(struct dio *dio, struct bio *bio)
>  				set_page_dirty_lock(page);
>  			page_cache_release(page);
>  		}
> -		err = bio->bi_error;
>  		bio_put(bio);
>  	}
> -	return err;
> +	return dio->io_error;
>  }
>  
>  /*
> --
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-- 
Carlos