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Subject: Re: [PATCH v3 RESEND] f2fs: introduce sb.required_features to store
 incompatible features
To:     Jaegeuk Kim <jaegeuk@kernel.org>
CC:     Chao Yu <chao@kernel.org>,
        <linux-f2fs-devel@lists.sourceforge.net>,
        <linux-kernel@vger.kernel.org>
References: <20190729150351.12223-1-chao@kernel.org>
 <20190730231850.GA7097@jaegeuk-macbookpro.roam.corp.google.com>
 <c7232d80-a4d8-88ae-2eca-01290dd0e56a@huawei.com>
 <20190801042215.GC84433@jaegeuk-macbookpro.roam.corp.google.com>
 <345c55ea-01c2-a9d1-4367-716dbd08ae9d@huawei.com>
 <20190801223509.GB27597@jaegeuk-macbookpro.roam.corp.google.com>
 <8e906ddb-81d8-b63e-0c19-1ee9fc7f5cbf@huawei.com>
 <20190806003522.GA98101@jaegeuk-macbookpro.roam.corp.google.com>
 <e48514d5-0f3f-8dd7-06ab-b7faf71101ba@huawei.com>
 <20190806012407.GB1029@jaegeuk-macbookpro.roam.corp.google.com>
From:   Chao Yu <yuchao0@huawei.com>
Message-ID: <103d1df0-eb5b-4854-0959-a84785eb85a8@huawei.com>
Date:   Tue, 6 Aug 2019 10:01:09 +0800
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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@huawei.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@huawei.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?

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
>>>>>>>>> .
>>>>>>>>>
>>>>>>> .
>>>>>>>
>>>>> .
>>>>>
>>> .
>>>
> .
>