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

From: Chao Yu
Date: Tue Oct 17 2017 - 09:36:27 EST


On 2017/10/17 17:07, 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@xxxxxxxx>

Reviewed-by: Chao Yu <yuchao0@xxxxxxxxxx>

Thanks,

> ---
> The warning is from mmotm. Andrew, please fold this fix into the
> patch that caused the warning, unless there are objections.
> ---
> 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++) {
>