Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Mon, 5 Aug 2019 18:24:07 -0700
From:   Jaegeuk Kim <jaegeuk@kernel.org>
To:     Chao Yu <yuchao0@huawei.com>
Cc:     Chao Yu <chao@kernel.org>, linux-f2fs-devel@lists.sourceforge.net,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 RESEND] f2fs: introduce sb.required_features to store
 incompatible features
Message-ID: <20190806012407.GB1029@jaegeuk-macbookpro.roam.corp.google.com>
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>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <e48514d5-0f3f-8dd7-06ab-b7faf71101ba@huawei.com>
User-Agent: Mutt/1.8.2 (2017-04-18)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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.

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