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SubjectRe: [PATCH v3 1/2] staging: erofs: add requirements field in superblock
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Hi Greg,

Sorry for annoying... Could you help merge these two fixes? Thanks in advance...
decompression inplace optimization needs these two patches and I will integrate
erofs decompression inplace optimization later for linux-next 5.3, and try to start
making effort on moving to fs/ directory on kernel 5.4...

Thanks,
Gao Xiang

On 2019/6/13 16:35, Gao Xiang wrote:
> There are some backward incompatible features 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+
> Reviewed-by: Chao Yu <yuchao0@huawei.com>
> Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
> ---
> change log v3:
> - record requirements in erofs_sb_info for runtime use as well;
>
> change log v2:
> - update printed message
>
> drivers/staging/erofs/erofs_fs.h | 13 ++++++++++---
> drivers/staging/erofs/internal.h | 2 ++
> drivers/staging/erofs/super.c | 19 +++++++++++++++++++
> 3 files changed, 31 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/staging/erofs/erofs_fs.h b/drivers/staging/erofs/erofs_fs.h
> index fa52898df006..8ddb2b3e7d39 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; /* (aka. feature_compat) */
> /* 12 */__u8 blkszbits; /* support block_size == PAGE_SIZE only */
> /* 13 */__u8 reserved;
>
> @@ -34,9 +40,10 @@ 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; /* (aka. feature_incompat) */
>
> -/* 80 */__u8 reserved2[48]; /* 128 bytes */
> -} __packed;
> +/* 84 */__u8 reserved2[44];
> +} __packed; /* 128 bytes */
>
> /*
> * erofs inode data mapping:
> diff --git a/drivers/staging/erofs/internal.h b/drivers/staging/erofs/internal.h
> index 911333cdeef4..fc732c86ecd8 100644
> --- a/drivers/staging/erofs/internal.h
> +++ b/drivers/staging/erofs/internal.h
> @@ -115,6 +115,8 @@ struct erofs_sb_info {
>
> u8 uuid[16]; /* 128-bit uuid for volume */
> u8 volume_name[16]; /* volume name */
> + u32 requirements;
> +
> char *dev_name;
>
> unsigned int mount_opt;
> diff --git a/drivers/staging/erofs/super.c b/drivers/staging/erofs/super.c
> index f580d4ef77a1..cadbcc11702a 100644
> --- a/drivers/staging/erofs/super.c
> +++ b/drivers/staging/erofs/super.c
> @@ -71,6 +71,22 @@ static void free_inode(struct inode *inode)
> kmem_cache_free(erofs_inode_cachep, vi);
> }
>
> +static bool check_layout_compatibility(struct super_block *sb,
> + struct erofs_super_block *layout)
> +{
> + const unsigned int requirements = le32_to_cpu(layout->requirements);
> +
> + EROFS_SB(sb)->requirements = requirements;
> +
> + /* check if current kernel meets all mandatory requirements */
> + if (requirements & (~EROFS_ALL_REQUIREMENTS)) {
> + errln("unidentified requirements %x, please upgrade kernel version",
> + requirements & ~EROFS_ALL_REQUIREMENTS);
> + return false;
> + }
> + return true;
> +}
> +
> static int superblock_read(struct super_block *sb)
> {
> struct erofs_sb_info *sbi;
> @@ -104,6 +120,9 @@ static int superblock_read(struct super_block *sb)
> goto out;
> }
>
> + if (!check_layout_compatibility(sb, layout))
> + 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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