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staging: erofs: add requirements field in superblock 

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: ba2b77a820 ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Gao Xiang 2019-06-13 16:35:41 +08:00 committed by Greg Kroah-Hartman
parent f2c7c76c5d
commit 5efe5137f0
3 changed files with 31 additions and 3 deletions
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13
drivers/staging/erofs/erofs_fs.h
View File

@ -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:

2
drivers/staging/erofs/internal.h
View File

@ -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;

19
drivers/staging/erofs/super.c
View File

@ -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