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Date:   Thu, 10 Jan 2019 11:28:12 +0100
From:   Jan Kara <jack@...e.cz>
To:     "zhangyi (F)" <yi.zhang@...wei.com>
Cc:     linux-ext4@...r.kernel.org, tytso@....edu,
        adilger.kernel@...ger.ca, jack@...e.cz, miaoxie@...wei.com
Subject: Re: [PATCH 1/2] jbd2: fix compile warning when using JBUFFER_TRACE

On Thu 10-01-19 14:06:38, zhangyi (F) wrote:
> The jh pointer may be used uninitialized in the two cases below and the
> compiler complain about it when enabling JBUFFER_TRACE macro, fix them.
> 
> In file included from fs/jbd2/transaction.c:19:0:
> fs/jbd2/transaction.c: In function ‘jbd2_journal_get_undo_access’:
> ./include/linux/jbd2.h:1637:38: warning: ‘jh’ is used uninitialized in this function [-Wuninitialized]
>  #define JBUFFER_TRACE(jh, info) do { printk("%s: %d\n", __func__, jh->b_jcount);} while (0)
>                                       ^
> fs/jbd2/transaction.c:1219:23: note: ‘jh’ was declared here
>   struct journal_head *jh;
>                        ^
> In file included from fs/jbd2/transaction.c:19:0:
> fs/jbd2/transaction.c: In function ‘jbd2_journal_dirty_metadata’:
> ./include/linux/jbd2.h:1637:38: warning: ‘jh’ may be used uninitialized in this function [-Wmaybe-uninitialized]
>  #define JBUFFER_TRACE(jh, info) do { printk("%s: %d\n", __func__, jh->b_jcount);} while (0)
>                                       ^
> fs/jbd2/transaction.c:1332:23: note: ‘jh’ was declared here
>   struct journal_head *jh;
>                        ^
> 
> Signed-off-by: zhangyi (F) <yi.zhang@...wei.com>
> Cc: stable@...r.kernel.org
> ---
>  fs/jbd2/transaction.c | 16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)

The patch looks good. Thanks! You can add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza


> 
> diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
> index c0b66a7..4b51177 100644
> --- a/fs/jbd2/transaction.c
> +++ b/fs/jbd2/transaction.c
> @@ -1219,11 +1219,12 @@ int jbd2_journal_get_undo_access(handle_t *handle, struct buffer_head *bh)
>  	struct journal_head *jh;
>  	char *committed_data = NULL;
>  
> -	JBUFFER_TRACE(jh, "entry");
>  	if (jbd2_write_access_granted(handle, bh, true))
>  		return 0;
>  
>  	jh = jbd2_journal_add_journal_head(bh);
> +	JBUFFER_TRACE(jh, "entry");
> +
>  	/*
>  	 * Do this first --- it can drop the journal lock, so we want to
>  	 * make sure that obtaining the committed_data is done
> @@ -1334,15 +1335,17 @@ int jbd2_journal_dirty_metadata(handle_t *handle, struct buffer_head *bh)
>  
>  	if (is_handle_aborted(handle))
>  		return -EROFS;
> -	if (!buffer_jbd(bh)) {
> -		ret = -EUCLEAN;
> -		goto out;
> -	}
> +	if (!buffer_jbd(bh))
> +		return -EUCLEAN;
> +
>  	/*
>  	 * We don't grab jh reference here since the buffer must be part
>  	 * of the running transaction.
>  	 */
>  	jh = bh2jh(bh);
> +	jbd_debug(5, "journal_head %p\n", jh);
> +	JBUFFER_TRACE(jh, "entry");
> +
>  	/*
>  	 * This and the following assertions are unreliable since we may see jh
>  	 * in inconsistent state unless we grab bh_state lock. But this is
> @@ -1376,9 +1379,6 @@ int jbd2_journal_dirty_metadata(handle_t *handle, struct buffer_head *bh)
>  	}
>  
>  	journal = transaction->t_journal;
> -	jbd_debug(5, "journal_head %p\n", jh);
> -	JBUFFER_TRACE(jh, "entry");
> -
>  	jbd_lock_bh_state(bh);
>  
>  	if (jh->b_modified == 0) {
> -- 
> 2.7.4
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR

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