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SubjectRe: [PATCH 3/6] f2fs: fix to avoid race condition when updating sbi flag
Hi Chao,

On Sun, Sep 18, 2016 at 11:30:05PM +0800, Chao Yu wrote:
> From: Chao Yu <yuchao0@huawei.com>
>
> Making updating of sbi flag atomic by using {test,set,clear}_bit,
> otherwise in concurrency scenario, the flag could be updated incorrectly.
>
> Signed-off-by: Chao Yu <yuchao0@huawei.com>
> ---
> fs/f2fs/f2fs.h | 10 ++++++----
> 1 file changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 9b4bbf2..c30f744b 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -794,7 +794,7 @@ struct f2fs_sb_info {
> struct proc_dir_entry *s_proc; /* proc entry */
> struct f2fs_super_block *raw_super; /* raw super block pointer */
> int valid_super_block; /* valid super block no */
> - int s_flag; /* flags for sbi */
> + unsigned long s_flag; /* flags for sbi */
>
> #ifdef CONFIG_F2FS_FS_ENCRYPTION
> u8 key_prefix[F2FS_KEY_DESC_PREFIX_SIZE];
> @@ -1063,17 +1063,19 @@ static inline struct address_space *NODE_MAPPING(struct f2fs_sb_info *sbi)
>
> static inline bool is_sbi_flag_set(struct f2fs_sb_info *sbi, unsigned int type)
> {
> - return sbi->s_flag & (0x01 << type);
> + return test_bit(type, &sbi->s_flag);
> }
>
> static inline void set_sbi_flag(struct f2fs_sb_info *sbi, unsigned int type)
> {
> - sbi->s_flag |= (0x01 << type);
> + if (!test_bit(type, &sbi->s_flag))
> + set_bit(type, &sbi->s_flag);

The set_bit() is enough, no?

> }
>
> static inline void clear_sbi_flag(struct f2fs_sb_info *sbi, unsigned int type)
> {
> - sbi->s_flag &= ~(0x01 << type);
> + if (test_bit(type, &sbi->s_flag))
> + clear_bit(type, &sbi->s_flag);

ditto.

Thanks,

> }
>
> static inline unsigned long long cur_cp_version(struct f2fs_checkpoint *cp)
> --
> 2.7.2

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