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Message-ID: <345c55ea-01c2-a9d1-4367-716dbd08ae9d@huawei.com>
Date: Thu, 1 Aug 2019 15:45:01 +0800
From: Chao Yu <yuchao0@...wei.com>
To: Jaegeuk Kim <jaegeuk@...nel.org>
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 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.
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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