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SubjectRe: [PATCH] f2fs: introduce on-disk layout version checking functionality
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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