ext4: change on-disk layout to support extended metadata checksumming

Define flags and change structure definitions to allow checksumming of
ext4 metadata.

Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

4 files changed, 63 insertions, 9 deletions

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 0e01e90add8b..61dd739b64f0 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -298,7 +298,9 @@ 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 */
@@ -308,7 +310,10 @@ 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;
 };
 
 /*
@@ -650,7 +655,8 @@ 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 */
@@ -666,7 +672,7 @@ 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) */
@@ -768,7 +774,7 @@ 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__)
 
@@ -1001,6 +1007,9 @@ 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
  */
@@ -1087,7 +1096,7 @@ 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 */
@@ -1113,7 +1122,8 @@ 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)
@@ -1414,6 +1424,12 @@ 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
@@ -1527,6 +1543,18 @@ 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.
  */
@@ -1541,6 +1569,8 @@ struct ext4_dir_entry_2 {
 
 #define EXT4_FT_MAX             8
 
+#define EXT4_FT_DIR_CSUM        0xDE
+
 /*
  * EXT4_DIR_PAD defines the directory entries boundaries
  *
@@ -1741,7 +1771,8 @@ 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 0f58b86e3a02..94822e74ef73 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 349d7b3671c8..b58bd5c8ffe7 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 25b7387ff183..91f31ca7d9af 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 {