[PATCH 1/2] staging: erofs: add requirements field in superblock

[PATCH 1/2] staging: erofs: add requirements field in superblock

[Gao Xiang]

There are some backward incompatible optimizations pending
for months, mainly due to on-disk format expensions.

However, we should ensure that it cannot be mounted with
old kernels. Otherwise, it will causes unexpected behaviors.

Fixes: ba2b77a82022 ("staging: erofs: add super block operations")
Cc: <stable@vger.kernel.org> # 4.19+
Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
---
 drivers/staging/erofs/erofs_fs.h | 11 +++++++++--
 drivers/staging/erofs/super.c    |  8 ++++++++
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/erofs/erofs_fs.h b/drivers/staging/erofs/erofs_fs.h
index fa52898df006..531821757845 100644
--- a/drivers/staging/erofs/erofs_fs.h
+++ b/drivers/staging/erofs/erofs_fs.h
@@ -17,10 +17,16 @@
 #define EROFS_SUPER_MAGIC_V1    0xE0F5E1E2
 #define EROFS_SUPER_OFFSET      1024
 
+/*
+ * Any bits that aren't in EROFS_ALL_REQUIREMENTS should be
+ * incompatible with this kernel version.
+ */
+#define EROFS_ALL_REQUIREMENTS  0
+
 struct erofs_super_block {
 /*  0 */__le32 magic;           /* in the little endian */
 /*  4 */__le32 checksum;        /* crc32c(super_block) */
-/*  8 */__le32 features;
+/*  8 */__le32 features;        /* extra features for the image */
 /* 12 */__u8 blkszbits;         /* support block_size == PAGE_SIZE only */
 /* 13 */__u8 reserved;
 
@@ -34,8 +40,9 @@ struct erofs_super_block {
 /* 44 */__le32 xattr_blkaddr;
 /* 48 */__u8 uuid[16];          /* 128-bit uuid for volume */
 /* 64 */__u8 volume_name[16];   /* volume name */
+/* 80 */__le32 requirements;    /* all mandatory minimum requirements */
 
-/* 80 */__u8 reserved2[48];     /* 128 bytes */
+/* 84 */__u8 reserved2[44];     /* 128 bytes */
 } __packed;
 
 /*
diff --git a/drivers/staging/erofs/super.c b/drivers/staging/erofs/super.c
index f580d4ef77a1..815e5825db59 100644
--- a/drivers/staging/erofs/super.c
+++ b/drivers/staging/erofs/super.c
@@ -104,6 +104,14 @@ static int superblock_read(struct super_block *sb)
 		goto out;
 	}
 
+	/* check if the kernel meets all mandatory requirements */
+	if (le32_to_cpu(layout->requirements) & (~EROFS_ALL_REQUIREMENTS)) {
+		errln("too old to meet minimum requirements: %x supported: %x",
+		      le32_to_cpu(layout->requirements),
+		      EROFS_ALL_REQUIREMENTS);
+		goto out;
+	}
+
 	sbi->blocks = le32_to_cpu(layout->blocks);
 	sbi->meta_blkaddr = le32_to_cpu(layout->meta_blkaddr);
 #ifdef CONFIG_EROFS_FS_XATTR
-- 
2.17.1

Re: [PATCH 1/2] staging: erofs: add requirements field in superblock

[Chao Yu]

On 2019/6/10 17:36, Gao Xiang wrote:
> There are some backward incompatible optimizations pending
> for months, mainly due to on-disk format expensions.
> 
> However, we should ensure that it cannot be mounted with
> old kernels. Otherwise, it will causes unexpected behaviors.
> 
> Fixes: ba2b77a82022 ("staging: erofs: add super block operations")
> Cc: <stable@vger.kernel.org> # 4.19+
> Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
> ---
>  drivers/staging/erofs/erofs_fs.h | 11 +++++++++--
>  drivers/staging/erofs/super.c    |  8 ++++++++
>  2 files changed, 17 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/staging/erofs/erofs_fs.h b/drivers/staging/erofs/erofs_fs.h
> index fa52898df006..531821757845 100644
> --- a/drivers/staging/erofs/erofs_fs.h
> +++ b/drivers/staging/erofs/erofs_fs.h
> @@ -17,10 +17,16 @@
>  #define EROFS_SUPER_MAGIC_V1    0xE0F5E1E2
>  #define EROFS_SUPER_OFFSET      1024
>  
> +/*
> + * Any bits that aren't in EROFS_ALL_REQUIREMENTS should be
> + * incompatible with this kernel version.
> + */
> +#define EROFS_ALL_REQUIREMENTS  0
> +
>  struct erofs_super_block {
>  /*  0 */__le32 magic;           /* in the little endian */
>  /*  4 */__le32 checksum;        /* crc32c(super_block) */
> -/*  8 */__le32 features;
> +/*  8 */__le32 features;        /* extra features for the image */
>  /* 12 */__u8 blkszbits;         /* support block_size == PAGE_SIZE only */
>  /* 13 */__u8 reserved;
>  
> @@ -34,8 +40,9 @@ struct erofs_super_block {
>  /* 44 */__le32 xattr_blkaddr;
>  /* 48 */__u8 uuid[16];          /* 128-bit uuid for volume */
>  /* 64 */__u8 volume_name[16];   /* volume name */
> +/* 80 */__le32 requirements;    /* all mandatory minimum requirements */
>  
> -/* 80 */__u8 reserved2[48];     /* 128 bytes */
> +/* 84 */__u8 reserved2[44];     /* 128 bytes */

Xiang,

It needs to update the comment behind reserved2, it's locating at 132 bytes.

>  } __packed;
>  
>  /*
> diff --git a/drivers/staging/erofs/super.c b/drivers/staging/erofs/super.c
> index f580d4ef77a1..815e5825db59 100644
> --- a/drivers/staging/erofs/super.c
> +++ b/drivers/staging/erofs/super.c
> @@ -104,6 +104,14 @@ static int superblock_read(struct super_block *sb)
>  		goto out;
>  	}
>  
> +	/* check if the kernel meets all mandatory requirements */
> +	if (le32_to_cpu(layout->requirements) & (~EROFS_ALL_REQUIREMENTS)) {
> +		errln("too old to meet minimum requirements: %x supported: %x",

It will be better to give a suggestion to user to upgrade kernel version to
match the image with new layout, otherwise it's just a little confused about
above printed message.

Thanks,

> +		      le32_to_cpu(layout->requirements),
> +		      EROFS_ALL_REQUIREMENTS);
> +		goto out;
> +	}
> +
>  	sbi->blocks = le32_to_cpu(layout->blocks);
>  	sbi->meta_blkaddr = le32_to_cpu(layout->meta_blkaddr);
>  #ifdef CONFIG_EROFS_FS_XATTR
> 

Re: [PATCH 1/2] staging: erofs: add requirements field in superblock

[Gao Xiang]

Hi Chao,

On 2019/6/11 9:37, Chao Yu wrote:
> On 2019/6/10 17:36, Gao Xiang wrote:
>> There are some backward incompatible optimizations pending
>> for months, mainly due to on-disk format expensions.
>>
>> However, we should ensure that it cannot be mounted with
>> old kernels. Otherwise, it will causes unexpected behaviors.
>>
>> Fixes: ba2b77a82022 ("staging: erofs: add super block operations")
>> Cc: <stable@vger.kernel.org> # 4.19+
>> Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
>> ---
>>  drivers/staging/erofs/erofs_fs.h | 11 +++++++++--
>>  drivers/staging/erofs/super.c    |  8 ++++++++
>>  2 files changed, 17 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/staging/erofs/erofs_fs.h b/drivers/staging/erofs/erofs_fs.h
>> index fa52898df006..531821757845 100644
>> --- a/drivers/staging/erofs/erofs_fs.h
>> +++ b/drivers/staging/erofs/erofs_fs.h
>> @@ -17,10 +17,16 @@
>>  #define EROFS_SUPER_MAGIC_V1    0xE0F5E1E2
>>  #define EROFS_SUPER_OFFSET      1024
>>  
>> +/*
>> + * Any bits that aren't in EROFS_ALL_REQUIREMENTS should be
>> + * incompatible with this kernel version.
>> + */
>> +#define EROFS_ALL_REQUIREMENTS  0
>> +
>>  struct erofs_super_block {
>>  /*  0 */__le32 magic;           /* in the little endian */
>>  /*  4 */__le32 checksum;        /* crc32c(super_block) */
>> -/*  8 */__le32 features;
>> +/*  8 */__le32 features;        /* extra features for the image */
>>  /* 12 */__u8 blkszbits;         /* support block_size == PAGE_SIZE only */
>>  /* 13 */__u8 reserved;
>>  
>> @@ -34,8 +40,9 @@ struct erofs_super_block {
>>  /* 44 */__le32 xattr_blkaddr;
>>  /* 48 */__u8 uuid[16];          /* 128-bit uuid for volume */
>>  /* 64 */__u8 volume_name[16];   /* volume name */
>> +/* 80 */__le32 requirements;    /* all mandatory minimum requirements */
>>  
>> -/* 80 */__u8 reserved2[48];     /* 128 bytes */
>> +/* 84 */__u8 reserved2[44];     /* 128 bytes */
> 
> Xiang,
> 
> It needs to update the comment behind reserved2, it's locating at 132 bytes.

I don't get the point... the whole struct is totally 128bytes I think?

> 
>>  } __packed;
>>  
>>  /*
>> diff --git a/drivers/staging/erofs/super.c b/drivers/staging/erofs/super.c
>> index f580d4ef77a1..815e5825db59 100644
>> --- a/drivers/staging/erofs/super.c
>> +++ b/drivers/staging/erofs/super.c
>> @@ -104,6 +104,14 @@ static int superblock_read(struct super_block *sb)
>>  		goto out;
>>  	}
>>  
>> +	/* check if the kernel meets all mandatory requirements */
>> +	if (le32_to_cpu(layout->requirements) & (~EROFS_ALL_REQUIREMENTS)) {
>> +		errln("too old to meet minimum requirements: %x supported: %x",
> 
> It will be better to give a suggestion to user to upgrade kernel version to
> match the image with new layout, otherwise it's just a little confused about
> above printed message.

OK, I will refine the printed message :)

Thanks,
Gao Xiang

> 
> Thanks,
> 
>> +		      le32_to_cpu(layout->requirements),
>> +		      EROFS_ALL_REQUIREMENTS);
>> +		goto out;
>> +	}
>> +
>>  	sbi->blocks = le32_to_cpu(layout->blocks);
>>  	sbi->meta_blkaddr = le32_to_cpu(layout->meta_blkaddr);
>>  #ifdef CONFIG_EROFS_FS_XATTR
>>

Re: [PATCH 1/2] staging: erofs: add requirements field in superblock

[Chao Yu]

On 2019/6/11 9:43, Gao Xiang wrote:
> Hi Chao,
> 
> On 2019/6/11 9:37, Chao Yu wrote:
>> On 2019/6/10 17:36, Gao Xiang wrote:
>>> There are some backward incompatible optimizations pending
>>> for months, mainly due to on-disk format expensions.
>>>
>>> However, we should ensure that it cannot be mounted with
>>> old kernels. Otherwise, it will causes unexpected behaviors.
>>>
>>> Fixes: ba2b77a82022 ("staging: erofs: add super block operations")
>>> Cc: <stable@vger.kernel.org> # 4.19+
>>> Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
>>> ---
>>>  drivers/staging/erofs/erofs_fs.h | 11 +++++++++--
>>>  drivers/staging/erofs/super.c    |  8 ++++++++
>>>  2 files changed, 17 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/staging/erofs/erofs_fs.h b/drivers/staging/erofs/erofs_fs.h
>>> index fa52898df006..531821757845 100644
>>> --- a/drivers/staging/erofs/erofs_fs.h
>>> +++ b/drivers/staging/erofs/erofs_fs.h
>>> @@ -17,10 +17,16 @@
>>>  #define EROFS_SUPER_MAGIC_V1    0xE0F5E1E2
>>>  #define EROFS_SUPER_OFFSET      1024
>>>  
>>> +/*
>>> + * Any bits that aren't in EROFS_ALL_REQUIREMENTS should be
>>> + * incompatible with this kernel version.
>>> + */
>>> +#define EROFS_ALL_REQUIREMENTS  0
>>> +
>>>  struct erofs_super_block {
>>>  /*  0 */__le32 magic;           /* in the little endian */
>>>  /*  4 */__le32 checksum;        /* crc32c(super_block) */
>>> -/*  8 */__le32 features;
>>> +/*  8 */__le32 features;        /* extra features for the image */
>>>  /* 12 */__u8 blkszbits;         /* support block_size == PAGE_SIZE only */
>>>  /* 13 */__u8 reserved;
>>>  
>>> @@ -34,8 +40,9 @@ struct erofs_super_block {
>>>  /* 44 */__le32 xattr_blkaddr;
>>>  /* 48 */__u8 uuid[16];          /* 128-bit uuid for volume */
>>>  /* 64 */__u8 volume_name[16];   /* volume name */
>>> +/* 80 */__le32 requirements;    /* all mandatory minimum requirements */
>>>  
>>> -/* 80 */__u8 reserved2[48];     /* 128 bytes */
>>> +/* 84 */__u8 reserved2[44];     /* 128 bytes */
>>
>> Xiang,
>>
>> It needs to update the comment behind reserved2, it's locating at 132 bytes.
> 
> I don't get the point... the whole struct is totally 128bytes I think?

Xiang, I misunderstood meaning of comments, please ignore it, sorry. :)

Thanks,

> 
>>
>>>  } __packed;
>>>  
>>>  /*
>>> diff --git a/drivers/staging/erofs/super.c b/drivers/staging/erofs/super.c
>>> index f580d4ef77a1..815e5825db59 100644
>>> --- a/drivers/staging/erofs/super.c
>>> +++ b/drivers/staging/erofs/super.c
>>> @@ -104,6 +104,14 @@ static int superblock_read(struct super_block *sb)
>>>  		goto out;
>>>  	}
>>>  
>>> +	/* check if the kernel meets all mandatory requirements */
>>> +	if (le32_to_cpu(layout->requirements) & (~EROFS_ALL_REQUIREMENTS)) {
>>> +		errln("too old to meet minimum requirements: %x supported: %x",
>>
>> It will be better to give a suggestion to user to upgrade kernel version to
>> match the image with new layout, otherwise it's just a little confused about
>> above printed message.
> 
> OK, I will refine the printed message :)
> 
> Thanks,
> Gao Xiang
> 
>>
>> Thanks,
>>
>>> +		      le32_to_cpu(layout->requirements),
>>> +		      EROFS_ALL_REQUIREMENTS);
>>> +		goto out;
>>> +	}
>>> +
>>>  	sbi->blocks = le32_to_cpu(layout->blocks);
>>>  	sbi->meta_blkaddr = le32_to_cpu(layout->meta_blkaddr);
>>>  #ifdef CONFIG_EROFS_FS_XATTR
>>>
> .
>