Subject: Re: [PATCH] block: zoned: fix harmless maybe-uninitialized warning
To: Arnd Bergmann <arnd@arndb.de>, Jens Axboe <axboe@kernel.dk>
References: <20161021154242.3707589-1-arnd@arndb.de>
CC: Shaun Tancheff <shaun@tancheff.com>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        Damien Le Moal <damien.lemoal@hgst.com>,
        Hannes Reinecke <hare@suse.de>, <linux-block@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>
From: Damien Le Moal <damien.lemoal@wdc.com>
Organization: Western Digital
Message-ID: <4a2b4842-3849-ead5-f3e2-774a9778eda6@wdc.com>
Date: Mon, 24 Oct 2016 08:38:39 +0900
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On 10/22/16 00:42, Arnd Bergmann wrote:
> The blkdev_report_zones produces a harmless warning when
> -Wmaybe-uninitialized is set, after gcc gets a little confused
> about the multiple 'goto' here:
> 
> block/blk-zoned.c: In function 'blkdev_report_zones':
> block/blk-zoned.c:188:13: error: 'nz' may be used uninitialized in this function [-Werror=maybe-uninitialized]
> 
> Moving the assignment to nr_zones makes this a little simpler
> while also avoiding the warning reliably. I'm removing the
> extraneous initialization of 'int ret' in the same patch, as
> that is semi-related and could cause an uninitialized use of
> that variable to not produce a warning.
> 
> Fixes: 6a0cb1bc106f ("block: Implement support for zoned block devices")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
>  block/blk-zoned.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/block/blk-zoned.c b/block/blk-zoned.c
> index 667f95d86695..472211fa183a 100644
> --- a/block/blk-zoned.c
> +++ b/block/blk-zoned.c
> @@ -80,7 +80,7 @@ int blkdev_report_zones(struct block_device *bdev,
>  	unsigned int i, n, nz;
>  	unsigned int ofst;
>  	void *addr;
> -	int ret = 0;
> +	int ret;
>  
>  	if (!q)
>  		return -ENXIO;
> @@ -179,14 +179,12 @@ int blkdev_report_zones(struct block_device *bdev,
>  
>  	}
>  
> +	*nr_zones = nz;
>  out:
>  	bio_for_each_segment_all(bv, bio, i)
>  		__free_page(bv->bv_page);
>  	bio_put(bio);
>  
> -	if (ret == 0)
> -		*nr_zones = nz;
> -
>  	return ret;
>  }
>  EXPORT_SYMBOL_GPL(blkdev_report_zones);

Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>

-- 
Damien Le Moal, Ph.D.
Sr. Manager, System Software Research Group,
Western Digital Corporation
Damien.LeMoal@wdc.com
(+81) 0466-98-3593 (ext. 513593)
1 kirihara-cho, Fujisawa,
Kanagawa, 252-0888 Japan
www.wdc.com, www.hgst.com