linux-kernel - Re: [PATCH] ext4: fix debug format string warning

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Date:   Fri, 9 Apr 2021 23:30:11 -0400
From:   tytso@....edu
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Andreas Dilger <adilger.kernel@...ger.ca>,
        Jan Kara <jack@...e.com>, Arnd Bergmann <arnd@...db.de>,
        Ritesh Harjani <riteshh@...ux.ibm.com>,
        Harshad Shirwadkar <harshadshirwadkar@...il.com>,
        kernel test robot <lkp@...el.com>,
        Daejun Park <daejun7.park@...sung.com>,
        Yi Li <yili@...hong.com>, Jens Axboe <axboe@...nel.dk>,
        Johannes Thumshirn <johannes.thumshirn@....com>,
        changfengnan <fengnanchang@...mail.com>,
        Shijie Luo <luoshijie1@...wei.com>, linux-ext4@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ext4: fix debug format string warning

On Fri, Apr 09, 2021 at 10:12:05PM +0200, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@...db.de>
> 
> Using no_printk() for jbd_debug() revealed two warnings:
> 
> fs/jbd2/recovery.c: In function 'fc_do_one_pass':
> fs/jbd2/recovery.c:256:30: error: format '%d' expects a matching 'int' argument [-Werror=format=]
>   256 |                 jbd_debug(3, "Processing fast commit blk with seq %d");
>       |                              ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> fs/ext4/fast_commit.c: In function 'ext4_fc_replay_add_range':
> fs/ext4/fast_commit.c:1732:30: error: format '%d' expects argument of type 'int', but argument 2 has type 'long unsigned int' [-Werror=format=]
>  1732 |                 jbd_debug(1, "Converting from %d to %d %lld",
> 
> The first one was added incorrectly, and was also missing a few newlines
> in debug output, and the second one happened when the type of an
> argument changed.
> 
> Reported-by: kernel test robot <lkp@...el.com>
> Fixes: d556435156b7 ("jbd2: avoid -Wempty-body warnings")
> Fixes: 6db074618969 ("ext4: use BIT() macro for BH_** state bits")
> Fixes: 5b849b5f96b4 ("jbd2: fast commit recovery path")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Thanks, applied, with one change.

> diff --git a/fs/jbd2/recovery.c b/fs/jbd2/recovery.c
> index 69f18fe20923..60601c5779f1 100644
> --- a/fs/jbd2/recovery.c
> +++ b/fs/jbd2/recovery.c
> @@ -245,15 +245,15 @@ static int fc_do_one_pass(journal_t *journal,
>     ....
>  
>  		if (err) {
> -			jbd_debug(3, "Fast commit replay: read error");
> +			jbd_debug(3, "Fast commit replay: read error\n");
>  			break;
>  		}
>  
> -		jbd_debug(3, "Processing fast commit blk with seq %d");
> +		jbd_debug(3, "Processing fast commit blk with seq\n");

This debug statement isn't adding any real value, so I just removed
it.

				- Ted