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Message-ID: <20190801223509.GB27597@jaegeuk-macbookpro.roam.corp.google.com>
Date: Thu, 1 Aug 2019 15:35:09 -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 08/01, 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
>
> 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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