linux-kernel - Re: [PATCH] f2fs: use extra parenthesis around assignment/condition

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Date:   Tue, 17 Oct 2017 11:51:14 +0200
From:   Jan Kara <jack@...e.cz>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Jan Kara <jack@...e.cz>, Andrew Morton <akpm@...ux-foundation.org>,
        Daniel Jordan <daniel.m.jordan@...cle.com>,
        Chao Yu <yuchao0@...wei.com>, Jaegeuk Kim <jaegeuk@...nel.org>,
        Kinglong Mee <kinglongmee@...il.com>,
        Yunlei He <heyunlei@...wei.com>,
        linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] f2fs: use extra parenthesis around assignment/condition

On Tue 17-10-17 11:07:12, Arnd Bergmann wrote:
> gcc warns that writing a while() loop with an assignment as the condition
> looks suspiciously like a comparison, and suggests a workaround:
> 
> fs/f2fs/checkpoint.c: In function 'sync_meta_pages':
> fs/f2fs/checkpoint.c:321:9: error: suggest parentheses around assignment used as truth value [-Werror=parentheses]
>   while (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
> 
> This seems reasonable, so let's do that.
> 
> Fixes: 4aba7297f4a5 ("f2fs: simplify page iteration loops")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
> The warning is from mmotm. Andrew, please fold this fix into the
> patch that caused the warning, unless there are objections.

Yeah, thanks for fixing this.

								Honza

> ---
>  fs/f2fs/checkpoint.c |  4 ++--
>  fs/f2fs/node.c       | 16 ++++++++--------
>  2 files changed, 10 insertions(+), 10 deletions(-)
> 
> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
> index 3ed9dcbf70ae..6124f8710dc3 100644
> --- a/fs/f2fs/checkpoint.c
> +++ b/fs/f2fs/checkpoint.c
> @@ -318,8 +318,8 @@ long sync_meta_pages(struct f2fs_sb_info *sbi, enum page_type type,
>  
>  	blk_start_plug(&plug);
>  
> -	while (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
> -				PAGECACHE_TAG_DIRTY)) {
> +	while ((nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
> +				PAGECACHE_TAG_DIRTY))) {
>  		int i;
>  
>  		for (i = 0; i < nr_pages; i++) {
> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
> index d4ceb9ebfe92..d6e4df0bb622 100644
> --- a/fs/f2fs/node.c
> +++ b/fs/f2fs/node.c
> @@ -1285,8 +1285,8 @@ static struct page *last_fsync_dnode(struct f2fs_sb_info *sbi, nid_t ino)
>  	pagevec_init(&pvec, 0);
>  	index = 0;
>  
> -	while (nr_pages = pagevec_lookup_tag(&pvec, NODE_MAPPING(sbi), &index,
> -				PAGECACHE_TAG_DIRTY)) {
> +	while ((nr_pages = pagevec_lookup_tag(&pvec, NODE_MAPPING(sbi), &index,
> +				PAGECACHE_TAG_DIRTY))) {
>  		int i;
>  
>  		for (i = 0; i < nr_pages; i++) {
> @@ -1439,8 +1439,8 @@ int fsync_node_pages(struct f2fs_sb_info *sbi, struct inode *inode,
>  	pagevec_init(&pvec, 0);
>  	index = 0;
>  
> -	while (nr_pages = pagevec_lookup_tag(&pvec, NODE_MAPPING(sbi), &index,
> -				PAGECACHE_TAG_DIRTY)) {
> +	while ((nr_pages = pagevec_lookup_tag(&pvec, NODE_MAPPING(sbi), &index,
> +				PAGECACHE_TAG_DIRTY))) {
>  		int i;
>  
>  		for (i = 0; i < nr_pages; i++) {
> @@ -1552,8 +1552,8 @@ int sync_node_pages(struct f2fs_sb_info *sbi, struct writeback_control *wbc,
>  next_step:
>  	index = 0;
>  
> -	while (nr_pages = pagevec_lookup_tag(&pvec, NODE_MAPPING(sbi), &index,
> -				PAGECACHE_TAG_DIRTY)) {
> +	while ((nr_pages = pagevec_lookup_tag(&pvec, NODE_MAPPING(sbi), &index,
> +				PAGECACHE_TAG_DIRTY))) {
>  		int i;
>  
>  		for (i = 0; i < nr_pages; i++) {
> @@ -1650,8 +1650,8 @@ int wait_on_node_pages_writeback(struct f2fs_sb_info *sbi, nid_t ino)
>  
>  	pagevec_init(&pvec, 0);
>  
> -	while (nr_pages = pagevec_lookup_tag(&pvec, NODE_MAPPING(sbi), &index,
> -				PAGECACHE_TAG_WRITEBACK)) {
> +	while ((nr_pages = pagevec_lookup_tag(&pvec, NODE_MAPPING(sbi), &index,
> +				PAGECACHE_TAG_WRITEBACK))) {
>  		int i;
>  
>  		for (i = 0; i < nr_pages; i++) {
> -- 
> 2.9.0
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR