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Message-ID: <20190806003522.GA98101@jaegeuk-macbookpro.roam.corp.google.com>
Date: Mon, 5 Aug 2019 17:35:22 -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 08/02, 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)
>
> 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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