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    Subject[PATCH 02/23] ext4: Change on-disk layout to support extended metadata checksumming
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    Date
    Define flags and change structure definitions to allow checksumming of ext4
    metadata.

    Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
    ---
    fs/ext4/ext4.h | 47 +++++++++++++++++++++++++++++++++++++++--------
    fs/ext4/ext4_extents.h | 13 +++++++++++++
    fs/ext4/namei.c | 8 ++++++++
    fs/ext4/xattr.h | 4 +++-
    4 files changed, 63 insertions(+), 9 deletions(-)


    diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
    index 513004f..0f0b0d5 100644
    --- a/fs/ext4/ext4.h
    +++ b/fs/ext4/ext4.h
    @@ -289,7 +289,9 @@ struct ext4_group_desc
    __le16 bg_free_inodes_count_lo;/* Free inodes count */
    __le16 bg_used_dirs_count_lo; /* Directories count */
    __le16 bg_flags; /* EXT4_BG_flags (INODE_UNINIT, etc) */
    - __u32 bg_reserved[2]; /* Likely block/inode bitmap checksum */
    + __le32 bg_exclude_bitmap_lo; /* Exclude bitmap for snapshots */
    + __le16 bg_block_bitmap_csum_lo;/* crc32c(s_uuid+grp_num+bbitmap) LE */
    + __le16 bg_inode_bitmap_csum_lo;/* crc32c(s_uuid+grp_num+ibitmap) LE */
    __le16 bg_itable_unused_lo; /* Unused inodes count */
    __le16 bg_checksum; /* crc16(sb_uuid+group+desc) */
    __le32 bg_block_bitmap_hi; /* Blocks bitmap block MSB */
    @@ -299,7 +301,10 @@ struct ext4_group_desc
    __le16 bg_free_inodes_count_hi;/* Free inodes count MSB */
    __le16 bg_used_dirs_count_hi; /* Directories count MSB */
    __le16 bg_itable_unused_hi; /* Unused inodes count MSB */
    - __u32 bg_reserved2[3];
    + __le32 bg_exclude_bitmap_hi; /* Exclude bitmap block MSB */
    + __le16 bg_block_bitmap_csum_hi;/* crc32c(s_uuid+grp_num+bbitmap) BE */
    + __le16 bg_inode_bitmap_csum_hi;/* crc32c(s_uuid+grp_num+ibitmap) BE */
    + __u32 bg_reserved;
    };

    /*
    @@ -641,7 +646,8 @@ struct ext4_inode {
    __le16 l_i_file_acl_high;
    __le16 l_i_uid_high; /* these 2 fields */
    __le16 l_i_gid_high; /* were reserved2[0] */
    - __u32 l_i_reserved2;
    + __le16 l_i_checksum_lo;/* crc32c(uuid+inum+inode) LE */
    + __le16 l_i_reserved;
    } linux2;
    struct {
    __le16 h_i_reserved1; /* Obsoleted fragment number/size which are removed in ext4 */
    @@ -657,7 +663,7 @@ struct ext4_inode {
    } masix2;
    } osd2; /* OS dependent 2 */
    __le16 i_extra_isize;
    - __le16 i_pad1;
    + __le16 i_checksum_hi; /* crc32c(uuid+inum+inode) BE */
    __le32 i_ctime_extra; /* extra Change time (nsec << 2 | epoch) */
    __le32 i_mtime_extra; /* extra Modification time(nsec << 2 | epoch) */
    __le32 i_atime_extra; /* extra Access time (nsec << 2 | epoch) */
    @@ -759,7 +765,7 @@ do { \
    #define i_gid_low i_gid
    #define i_uid_high osd2.linux2.l_i_uid_high
    #define i_gid_high osd2.linux2.l_i_gid_high
    -#define i_reserved2 osd2.linux2.l_i_reserved2
    +#define i_checksum_lo osd2.linux2.l_i_checksum_lo

    #elif defined(__GNU__)

    @@ -992,6 +998,9 @@ extern void ext4_set_bits(void *bm, int cur, int len);
    #define EXT4_ERRORS_PANIC 3 /* Panic */
    #define EXT4_ERRORS_DEFAULT EXT4_ERRORS_CONTINUE

    +/* Metadata checksum algorithm codes */
    +#define EXT4_CRC32C_CHKSUM 1
    +
    /*
    * Structure of the super block
    */
    @@ -1078,7 +1087,7 @@ struct ext4_super_block {
    __le64 s_mmp_block; /* Block for multi-mount protection */
    __le32 s_raid_stripe_width; /* blocks on all data disks (N*stride)*/
    __u8 s_log_groups_per_flex; /* FLEX_BG group size */
    - __u8 s_reserved_char_pad;
    + __u8 s_checksum_type; /* metadata checksum algorithm used */
    __le16 s_reserved_pad;
    __le64 s_kbytes_written; /* nr of lifetime kilobytes written */
    __le32 s_snapshot_inum; /* Inode number of active snapshot */
    @@ -1104,7 +1113,8 @@ struct ext4_super_block {
    __le32 s_usr_quota_inum; /* inode for tracking user quota */
    __le32 s_grp_quota_inum; /* inode for tracking group quota */
    __le32 s_overhead_clusters; /* overhead blocks/clusters in fs */
    - __le32 s_reserved[109]; /* Padding to the end of the block */
    + __le32 s_reserved[108]; /* Padding to the end of the block */
    + __le32 s_checksum; /* crc32c(superblock) */
    };

    #define EXT4_S_ERR_LEN (EXT4_S_ERR_END - EXT4_S_ERR_START)
    @@ -1407,6 +1417,12 @@ static inline void ext4_clear_state_flags(struct ext4_inode_info *ei)
    #define EXT4_FEATURE_RO_COMPAT_EXTRA_ISIZE 0x0040
    #define EXT4_FEATURE_RO_COMPAT_QUOTA 0x0100
    #define EXT4_FEATURE_RO_COMPAT_BIGALLOC 0x0200
    +/*
    + * METADATA_CSUM also enables group descriptor checksums (GDT_CSUM). When
    + * METADATA_CSUM is set, group descriptor checksums use the same algorithm as
    + * all other data structures' checksums. However, the METADATA_CSUM and
    + * GDT_CSUM bits are mutually exclusive.
    + */
    #define EXT4_FEATURE_RO_COMPAT_METADATA_CSUM 0x0400

    #define EXT4_FEATURE_INCOMPAT_COMPRESSION 0x0001
    @@ -1519,6 +1535,18 @@ struct ext4_dir_entry_2 {
    };

    /*
    + * This is a bogus directory entry at the end of each leaf block that
    + * records checksums.
    + */
    +struct ext4_dir_entry_tail {
    + __le32 det_reserved_zero1; /* Pretend to be unused */
    + __le16 det_rec_len; /* 12 */
    + __u8 det_reserved_zero2; /* Zero name length */
    + __u8 det_reserved_ft; /* 0xDE, fake file type */
    + __le32 det_checksum; /* crc32c(uuid+inum+dirblock) */
    +};
    +
    +/*
    * Ext4 directory file types. Only the low 3 bits are used. The
    * other bits are reserved for now.
    */
    @@ -1533,6 +1561,8 @@ struct ext4_dir_entry_2 {

    #define EXT4_FT_MAX 8

    +#define EXT4_FT_DIR_CSUM 0xDE
    +
    /*
    * EXT4_DIR_PAD defines the directory entries boundaries
    *
    @@ -1729,7 +1759,8 @@ struct mmp_struct {
    __le16 mmp_check_interval;

    __le16 mmp_pad1;
    - __le32 mmp_pad2[227];
    + __le32 mmp_pad2[226];
    + __le32 mmp_checksum; /* crc32c(uuid+mmp_block) */
    };

    /* arguments passed to the mmp thread */
    diff --git a/fs/ext4/ext4_extents.h b/fs/ext4/ext4_extents.h
    index a52db3a..5c7fbade 100644
    --- a/fs/ext4/ext4_extents.h
    +++ b/fs/ext4/ext4_extents.h
    @@ -63,9 +63,22 @@
    * ext4_inode has i_block array (60 bytes total).
    * The first 12 bytes store ext4_extent_header;
    * the remainder stores an array of ext4_extent.
    + * For non-inode extent blocks, ext4_extent_tail
    + * follows the array.
    */

    /*
    + * This is the extent tail on-disk structure.
    + * All other extent structures are 12 bytes long. It turns out that
    + * block_size % 12 >= 4 for at least all powers of 2 greater than 512, which
    + * covers all valid ext4 block sizes. Therefore, this tail structure can be
    + * crammed into the end of the block without having to rebalance the tree.
    + */
    +struct ext4_extent_tail {
    + __le32 et_checksum; /* crc32c(uuid+inum+extent_block) */
    +};
    +
    +/*
    * This is the extent on-disk structure.
    * It's used at the bottom of the tree.
    */
    diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
    index 2043f48..8b56fdf 100644
    --- a/fs/ext4/namei.c
    +++ b/fs/ext4/namei.c
    @@ -145,6 +145,14 @@ struct dx_map_entry
    u16 size;
    };

    +/*
    + * This goes at the end of each htree block.
    + */
    +struct dx_tail {
    + u32 dt_reserved;
    + __le32 dt_checksum; /* crc32c(uuid+inum+dirblock) */
    +};
    +
    static inline ext4_lblk_t dx_get_block(struct dx_entry *entry);
    static void dx_set_block(struct dx_entry *entry, ext4_lblk_t value);
    static inline unsigned dx_get_hash(struct dx_entry *entry);
    diff --git a/fs/ext4/xattr.h b/fs/ext4/xattr.h
    index 25b7387..91f31ca 100644
    --- a/fs/ext4/xattr.h
    +++ b/fs/ext4/xattr.h
    @@ -27,7 +27,9 @@ struct ext4_xattr_header {
    __le32 h_refcount; /* reference count */
    __le32 h_blocks; /* number of disk blocks used */
    __le32 h_hash; /* hash value of all attributes */
    - __u32 h_reserved[4]; /* zero right now */
    + __le32 h_checksum; /* crc32c(uuid+id+xattrblock) */
    + /* id = inum if refcount=1, blknum otherwise */
    + __u32 h_reserved[3]; /* zero right now */
    };

    struct ext4_xattr_ibody_header {


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