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@xxxxxxxxxxxxxxx> # 4.19+
>> Signed-off-by: Gao Xiang <gaoxiang25@xxxxxxxxxx>
>> ---
>> 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
>>
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