Message-ID: <20190806021144.GB7280@jaegeuk-macbookpro.roam.corp.google.com>
Date:   Mon, 5 Aug 2019 19:11:44 -0700
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Chao Yu <yuchao0@...wei.com>
Cc:     Chao Yu <chao@...nel.org>, linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 RESEND] f2fs: introduce sb.required_features to store
 incompatible features

On 08/06, Chao Yu wrote:
> On 2019/8/6 9:24, Jaegeuk Kim wrote:
> > On 08/06, Chao Yu wrote:
> >> On 2019/8/6 8:35, Jaegeuk Kim wrote:
> >>> 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@...wei.com>
> >>>>>>>>>>
> >>>>>>>>>> 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@...wei.com>
> >>>>>>>>>> ---
> >>>>>>>>>> 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)
> >>
> >> Sorry, I'm not sure whether I have understood your point... :(
> >>
> >> IIUC of your point, we have defined F2FS_FEATURE_SUPPORT (0x0BFF) which excludes
> >> F2FS_FEATURE_VERITY (0x0400) feature bit, then once verity feature merged in
> >> kernel, we can add it into F2FS_FEATURE_SUPPORT, any problem we may face here?
> > 
> > I was thinking the cases like "don't care features" made by mkfs. For example,
> > mkfs can set F2FS_FEATURE_BLKZONED, which doesn't need f2fs being supported.
> 
> Yes, I can understand this.
> 
> So F2FS_FEATURE_SUPPORT can exclude them directly?

No, I'd like to control it via mkfs. Kernel always needs to say what they can
support, IIUC your point.

> 
> excluded:
> 
> #define F2FS_FEATURE_BLKZONED		0x0002
> #define F2FS_FEATURE_ATOMIC_WRITE	0x0004
> #define F2FS_FEATURE_LOST_FOUND		0x0200
> 
> included:
> 
> #define F2FS_FEATURE_ENCRYPT		0x0001
> #define F2FS_FEATURE_EXTRA_ATTR		0x0008
> #define F2FS_FEATURE_PRJQUOTA		0x0010
> #define F2FS_FEATURE_INODE_CHKSUM	0x0020
> #define F2FS_FEATURE_FLEXIBLE_INLINE_XATTR	0x0040
> #define F2FS_FEATURE_QUOTA_INO		0x0080
> #define F2FS_FEATURE_INODE_CRTIME	0x0100
> #define F2FS_FEATURE_SB_CHKSUM		0x0800
> //#define F2FS_FEATURE_VERITY		0x0400	/* reserved */
> #define F2FS_FEATURE_CASEFOLD		0x1000
> 
> #define F2FS_FEATURE_SUPPORT		0x19B9
> 
> Thanks,
> 
> > 
> >>
> >> Thanks
> >>
> >>>
> >>>>
> >>>> 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
> >>>>>>>>> .
> >>>>>>>>>
> >>>>>>> .
> >>>>>>>
> >>>>> .
> >>>>>
> >>> .
> >>>
> > .
> > 

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