From 5efe5137f05bbb4688890620934538c005e7d1d6 Mon Sep 17 00:00:00 2001 From: Gao Xiang Date: Thu, 13 Jun 2019 16:35:41 +0800 Subject: [PATCH] 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: ba2b77a82022 ("staging: erofs: add super block operations") Cc: # 4.19+ Reviewed-by: Chao Yu Signed-off-by: Gao Xiang Signed-off-by: Greg Kroah-Hartman --- 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 fa52898..8ddb2b3 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 c47778b..382258f 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 f580d4ef..cadbcc1 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 -- 2.7.4