Re: [PATCH v2 2/6] exfat: introduce exfat_fat_walk helper

[Yuezhang.Mo@xxxxxxxx]

> From: Chi Zhiling <chizhiling@xxxxxxxxxx>
> 
> Introduce exfat_fat_walk() to walk the FAT chain by a given step,
> handling both ALLOC_NO_FAT_CHAIN and ALLOC_FAT_CHAIN modes. Also
> redefine exfat_get_next_cluster as a thin wrapper around it for
> backward compatibility.
> 
> Signed-off-by: Chi Zhiling <chizhiling@xxxxxxxxxx>
> ---
>  fs/exfat/exfat_fs.h | 23 ++++++++++++++++++++++-
>  1 file changed, 22 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/exfat/exfat_fs.h b/fs/exfat/exfat_fs.h
> index 9fed9fb33cae..530459ab9acc 100644
> --- a/fs/exfat/exfat_fs.h
> +++ b/fs/exfat/exfat_fs.h
> @@ -437,7 +437,8 @@ int exfat_set_volume_dirty(struct super_block *sb);
>  int exfat_clear_volume_dirty(struct super_block *sb);
> 
>  /* fatent.c */
> -#define exfat_get_next_cluster(sb, pclu) exfat_ent_get(sb, *(pclu), pclu, NULL)
> +#define exfat_get_next_cluster(sb, pclu) \
> +       exfat_fat_walk(sb, (pclu), 1, ALLOC_FAT_CHAIN)
> 
>  int exfat_alloc_cluster(struct inode *inode, unsigned int num_alloc,
>                 struct exfat_chain *p_chain, bool sync_bmap);
> @@ -456,6 +457,26 @@ int exfat_count_num_clusters(struct super_block *sb,
>  int exfat_blk_readahead(struct super_block *sb, sector_t sec,
>                 sector_t *ra, blkcnt_t *ra_cnt, sector_t end);
> 
> +static inline int
> +exfat_fat_walk(struct super_block *sb, unsigned int *clu,
> +               unsigned int step, int flags)
> +{
> +       struct buffer_head *bh = NULL;
> +
> +       if (flags == ALLOC_NO_FAT_CHAIN) {
> +               (*clu) += step;
> +               return 0;
> +       }

For ALLOC_NO_FAT_CHAIN, since the FAT region is not accessed, it would be
better to use a more general function name, such as exfat_cluster_walk.

> +
> +       while (step--) {
> +               if (exfat_ent_get(sb, *clu, clu, &bh))
> +                       return -EIO;
> +       }
> +       brelse(bh);
> +
> +       return 0;
> +}
> +
>  /* balloc.c */
>  int exfat_load_bitmap(struct super_block *sb);
>  void exfat_free_bitmap(struct exfat_sb_info *sbi);
> --
> 2.43.0