Re: [PATCH v3 RESEND] f2fs: introduce sb.required_features to store incompatible features

[Jaegeuk Kim]

On 08/02, Chao Yu wrote:
> On 2019/8/2 6:35, Jaegeuk Kim wrote:
> > On 08/01, Chao Yu wrote:
> >> On 2019/8/1 12:22, Jaegeuk Kim wrote:
> >>> On 07/31, Chao Yu wrote:
> >>>> On 2019/7/31 7:18, Jaegeuk Kim wrote:
> >>>>> On 07/29, Chao Yu wrote:
> >>>>>> From: Chao Yu <yuchao0@xxxxxxxxxx>
> >>>>>>
> >>>>>> Later after this patch was merged, all new incompatible feature's
> >>>>>> bit should be added into sb.required_features field, and define new
> >>>>>> feature function with F2FS_INCOMPAT_FEATURE_FUNCS() macro.
> >>>>>>
> >>>>>> Then during mount, we will do sanity check with enabled features in
> >>>>>> image, if there are features in sb.required_features that kernel can
> >>>>>> not recognize, just fail the mount.
> >>>>>>
> >>>>>> Signed-off-by: Chao Yu <yuchao0@xxxxxxxxxx>
> >>>>>> ---
> >>>>>> v3:
> >>>>>> - change commit title.
> >>>>>> - fix wrong macro name.
> >>>>>>  fs/f2fs/f2fs.h          | 15 +++++++++++++++
> >>>>>>  fs/f2fs/super.c         | 10 ++++++++++
> >>>>>>  include/linux/f2fs_fs.h |  3 ++-
> >>>>>>  3 files changed, 27 insertions(+), 1 deletion(-)
> >>>>>>
> >>>>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> >>>>>> index a6eb828af57f..b8e17d4ddb8d 100644
> >>>>>> --- a/fs/f2fs/f2fs.h
> >>>>>> +++ b/fs/f2fs/f2fs.h
> >>>>>> @@ -163,6 +163,15 @@ struct f2fs_mount_info {
> >>>>>>  #define F2FS_CLEAR_FEATURE(sbi, mask)					\
> >>>>>>  	(sbi->raw_super->feature &= ~cpu_to_le32(mask))
> >>>>>>  
> >>>>>> +#define F2FS_INCOMPAT_FEATURES		0
> >>>>>> +
> >>>>>> +#define F2FS_HAS_INCOMPAT_FEATURE(sbi, mask)				\
> >>>>>> +	((sbi->raw_super->required_features & cpu_to_le32(mask)) != 0)
> >>>>>> +#define F2FS_SET_INCOMPAT_FEATURE(sbi, mask)				\
> >>>>>> +	(sbi->raw_super->required_features |= cpu_to_le32(mask))
> >>>>>> +#define F2FS_CLEAR_INCOMPAT_FEATURE(sbi, mask)				\
> >>>>>> +	(sbi->raw_super->required_features &= ~cpu_to_le32(mask))
> >>>>>> +
> >>>>>>  /*
> >>>>>>   * Default values for user and/or group using reserved blocks
> >>>>>>   */
> >>>>>> @@ -3585,6 +3594,12 @@ F2FS_FEATURE_FUNCS(lost_found, LOST_FOUND);
> >>>>>>  F2FS_FEATURE_FUNCS(sb_chksum, SB_CHKSUM);
> >>>>>>  F2FS_FEATURE_FUNCS(casefold, CASEFOLD);
> >>>>>>  
> >>>>>> +#define F2FS_INCOMPAT_FEATURE_FUNCS(name, flagname) \
> >>>>>> +static inline int f2fs_sb_has_##name(struct f2fs_sb_info *sbi) \
> >>>>>> +{ \
> >>>>>> +	return F2FS_HAS_INCOMPAT_FEATURE(sbi, F2FS_FEATURE_##flagname); \
> >>>>>> +}
> >>>>>> +
> >>>>>>  #ifdef CONFIG_BLK_DEV_ZONED
> >>>>>>  static inline bool f2fs_blkz_is_seq(struct f2fs_sb_info *sbi, int devi,
> >>>>>>  				    block_t blkaddr)
> >>>>>> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> >>>>>> index 5540fee0fe3f..3701dcce90e6 100644
> >>>>>> --- a/fs/f2fs/super.c
> >>>>>> +++ b/fs/f2fs/super.c
> >>>>>> @@ -2513,6 +2513,16 @@ static int sanity_check_raw_super(struct f2fs_sb_info *sbi,
> >>>>>>  		return -EINVAL;
> >>>>>>  	}
> >>>>>>  
> >>>>>> +	/* check whether current kernel supports all features on image */
> >>>>>> +	if (le32_to_cpu(raw_super->required_features) &
> >>>>>
> >>>>> ...
> >>>>> #define F2FS_FEATURE_VERITY	0x0400	/* reserved */
> >>>>> ...
> >>>>> #define F2FS_FEATURE_CASEFOLD	0x1000
> >>>>> #define F2FS_FEATURE_SUPPORT	0x1BFF
> >>>>>
> >>>>> 	if (le32_to_cpu(raw_super->required_features) & ~F2FS_FEATURE_SUPPORT) {
> >>>>> 		...
> >>>>> 		return -EINVAL;
> >>>>> 	}
> >>>>
> >>>> Um, I thought .required_features are used to store new feature flags from 0x0.
> >>>>
> >>>> All 'F2FS_FEATURE_SUPPORT' bits should be stored in sb.feature instead of
> >>>> sb.required_features, I'm confused...
> >>>
> >>> I'm thinking,
> >>>
> >>> f2fs-tools     sb->required_features     f2fs    F2FS_FEATURE_SUPPORT
> >>> v0             0                         v0      no_check -> ok
> >>> v1             0x1BFF                    v0      no_check -> ok
> >>> v0             0                         v1      0x1BFF -> ok
> >>> v1             0x1BFF                    v1      0x1BFF -> ok
> >>> v2             0x3BFF                    v1      0x1BFF -> fail
> >>> v1             0x1BFF                    v2      0x3BFF -> ok
> >>> v2             0x3BFF                    v2      0x3BFF -> ok
> >>
> >> I see, it's a bit waste for 0x1FFF low bits in sb->required_features. Why not
> >> leaving 0x0FFF in sb->feature w/o sanity check. And make all new incompatible
> >> features (including casefold) adding into sb->required_features.
> > 
> > I don't think we can define like this, and we still have 32bits feature filed.
> > This would give another confusion to understand. VERITY is reserved only now.
> > 
> > #define F2FS_FEATURE_CASEFOLD		0x0001
> 
> Oops, so you want to make .required_features being almost a mirror of .feature,
> and do sanity check on it... I can see now. :P
> 
> If so, why not just use .feature:

Sometimes, we don't need to set the flag, but not required at some point.
(e.g., verify)

> 
> kernel	tool
> v5.2 .. 1.12
> #define	F2FS_FEATURE_SUPPORT		0x0BFF
> 
> v5.3 .. 1.13
> #define F2FS_FEATURE_CASEFOLD		0x1000
> #define	F2FS_FEATURE_SUPPORT		0x1BFF
> 
> v5.4 .. 1.14
> #define F2FS_FEATURE_CASEFOLD		0x1000
> #define F2FS_FEATURE_COMPRESS		0x2000
> #define	F2FS_FEATURE_SUPPORT		0x3BFF
> 
> f2fs-tools	sb->feature		f2fs	F2FS_FEATURE_SUPPORT
> 
> [enable all features in tools]
> v1.12		0x0BFF			v5.2	no_check -> ok
> v1.12		0x0BFF			v5.3	0x1BFF -> ok
> v1.12		0x0BFF			v5.4	0x3BFF -> ok
> 
> v1.13		0x1BFF			v5.2	that's issue we need to fix
> v1.13		0x1BFF			v5.3	0x1BFF -> ok
> v1.13		0x1BFF			v5.4	0x3BFF -> ok
> 
> v1.14		0x3BFF			v5.2	that's issue we need to fix
> v1.14		0x3BFF			v5.3	0x1BFF -> fail
> v1.14		0x3BFF			v5.4	0x3BFF -> ok
> 
> Or am I missing something?
> 
> Thanks,
> 
> > 
> >>
> >> Then that would be:
> >>
> >> kernel	tool
> >> v5.2 .. 1.12
> >> #define	F2FS_FEATURE_SUPPORT		0x0000
> >>
> >> v5.3 .. 1.13
> >> #define F2FS_FEATURE_CASEFOLD		0x0001
> >> #define	F2FS_FEATURE_SUPPORT		0x0001
> >>
> >> v5.4 .. 1.14
> >> #define F2FS_FEATURE_CASEFOLD		0x0001
> >> #define F2FS_FEATURE_COMPRESS		0x0002
> >> #define	F2FS_FEATURE_SUPPORT		0x0003
> >>
> >> f2fs-tools	sb->required_features	f2fs	F2FS_FEATURE_SUPPORT
> >>
> >> v1.12		0x0000			v5.2	no_check -> ok
> >> v1.12		0x0000			v5.3	0x0001 -> ok
> >> v1.12		0x0000			v5.4	0x0003 -> ok
> >>
> >> v1.13		0x0001			v5.2	that's issue we need to fix
> >> v1.13		0x0001			v5.3	0x0001 -> ok
> >> v1.13		0x0001			v5.4	0x0003 -> ok
> >>
> >> v1.14		0x0003			v5.2	that's issue we need to fix
> >> v1.14		0x0003			v5.3	0x0001 -> fail
> >> v1.14		0x0003			v5.4	0x0003 -> ok
> >>
> >> And all compatible features can be added into sb->feature[_VERITY, ....].
> >>
> >> Would that okay to you?
> >>
> >> Thanks,
> >>
> >>>
> >>>>
> >>>> Thanks,
> >>>>
> >>>>>
> >>>>>
> >>>>>> +			~F2FS_INCOMPAT_FEATURES) {
> >>>>>> +		f2fs_info(sbi, "Unsupported feature: %x: supported: %x",
> >>>>>> +			  le32_to_cpu(raw_super->required_features) ^
> >>>>>> +			  F2FS_INCOMPAT_FEATURES,
> >>>>>> +			  F2FS_INCOMPAT_FEATURES);
> >>>>>> +		return -EINVAL;
> >>>>>> +	}
> >>>>>> +
> >>>>>>  	/* Check checksum_offset and crc in superblock */
> >>>>>>  	if (__F2FS_HAS_FEATURE(raw_super, F2FS_FEATURE_SB_CHKSUM)) {
> >>>>>>  		crc_offset = le32_to_cpu(raw_super->checksum_offset);
> >>>>>> diff --git a/include/linux/f2fs_fs.h b/include/linux/f2fs_fs.h
> >>>>>> index a2b36b2e286f..4141be3f219c 100644
> >>>>>> --- a/include/linux/f2fs_fs.h
> >>>>>> +++ b/include/linux/f2fs_fs.h
> >>>>>> @@ -117,7 +117,8 @@ struct f2fs_super_block {
> >>>>>>  	__u8 hot_ext_count;		/* # of hot file extension */
> >>>>>>  	__le16	s_encoding;		/* Filename charset encoding */
> >>>>>>  	__le16	s_encoding_flags;	/* Filename charset encoding flags */
> >>>>>> -	__u8 reserved[306];		/* valid reserved region */
> >>>>>> +	__le32 required_features;       /* incompatible features to old kernel */
> >>>>>> +	__u8 reserved[302];		/* valid reserved region */
> >>>>>>  	__le32 crc;			/* checksum of superblock */
> >>>>>>  } __packed;
> >>>>>>  
> >>>>>> -- 
> >>>>>> 2.22.0
> >>>>> .
> >>>>>
> >>> .
> >>>
> > .
> >