Hi Slava,

On Thu, May 19, 2016 at 10:46:06AM -0700, Viacheslav Dubeyko wrote:
...
>  
> +#ifdef CONFIG_F2FS_16TB_VOLUME_SUPPORT
> +#define F2FS_MAX_SUPP_MAJOR_VERSION          (2)
> +#define F2FS_MIN_16TB_VOLUME_SUPPORT_VERSION (2)
> +#else
> +#define F2FS_MAX_SUPP_MAJOR_VERSION          (1)
> +#endif
> +
...
>  
> +static int f2fs_check_version_and_features(struct super_block *sb,
> +                                        struct f2fs_super_block *raw_super)
> +{
> +     u16 major_ver = le16_to_cpu(raw_super->major_ver);
> +     u32 feature = le32_to_cpu(raw_super->feature);
> +
> +     if (major_ver > F2FS_MAX_SUPP_MAJOR_VERSION) {

This means, for example, f2fs driver in v4.8 will deny to mount a partition
formatted by mkfs.f2fs v3.x, which doesn't make sense, IIUC.

As Christoph mentioned, how about checking the feature only like this?

1. if the feature is ON,
 - go 64 bits   , when compiled w/  F2FS_MIN_16TB_VOLUME_SUPPORT
 - fail to mount, when compiled w/o F2FS_MIN_16TB_VOLUME_SUPPORT

2. if the feature is OFF,
 - fail to mount, when compiled w/  F2FS_MIN_16TB_VOLUME_SUPPORT
 - go 32 bits   , when compiled w/o F2FS_MIN_16TB_VOLUME_SUPPORT

Thoughts?

Thanks,

> +             f2fs_msg(sb, KERN_CRIT,
> +                      "Failed to mount volume: "
> +                      "major version %u, max supported version %u",
> +                      major_ver,
> +                      F2FS_MAX_SUPP_MAJOR_VERSION);
> +             return -EOPNOTSUPP;
> +     }
> +
> +#ifdef CONFIG_F2FS_16TB_VOLUME_SUPPORT
> +
> +     if (major_ver < F2FS_MIN_16TB_VOLUME_SUPPORT_VERSION) {
> +             if (feature & F2FS_FEATURE_16TB_SUPPORT) {
> +                     f2fs_msg(sb, KERN_CRIT,
> +                              "Failed to mount corrupted volume. "
> +                              "Please, check the volume by FSCK utility.");
> +                     return -EOPNOTSUPP;
> +             }
> +     } else {
> +             if (!(feature & F2FS_FEATURE_16TB_SUPPORT)) {
> +                     f2fs_msg(sb, KERN_CRIT,
> +                              "Failed to mount corrupted volume. "
> +                              "Please, check the volume by FSCK utility.");
> +                     return -EOPNOTSUPP;
> +             }
> +     }
> +
> +#else
> +
> +     if (feature & F2FS_FEATURE_16TB_SUPPORT) {
> +             f2fs_msg(sb, KERN_CRIT,
> +                      "Failed to mount corrupted volume. "
> +                      "Please, check the volume by FSCK utility.");
> +             return -EOPNOTSUPP;
> +     }
> +
> +#endif
> +
> +     return 0;
> +}
> +
>  static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
>  {
>       struct f2fs_sb_info *sbi;
> @@ -1360,6 +1407,10 @@ try_onemore:
>       if (err)
>               goto free_sbi;
>  
> +     err = f2fs_check_version_and_features(sb, raw_super);
> +     if (err)
> +             goto free_sbi;
> +
>       sb->s_fs_info = sbi;
>       default_options(sbi);
>       /* parse mount options */
> -- 
> 1.9.1
> 
> 

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