xfs: remove the magic numbers in xfs_btree_block-related len macros

replace the magic numbers by offsetof(...) and sizeof(...), and add two
extra checks on xfs_check_ondisk_structs()

[dchinner: renamed header structures to be more descriptive]

Signed-off-by: Hou Tao <houtao1@huawei.com>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

diff --git a/fs/xfs/libxfs/xfs_format.h b/fs/xfs/libxfs/xfs_format.h
index dc97eb21af071b0e040fe0d74b8ba51214e28cf9..adb204d40f2246c181051566e385463f077e15ca 100644 (file)
--- a/fs/xfs/libxfs/xfs_format.h
+++ b/fs/xfs/libxfs/xfs_format.h
@@ -1435,41 +1435,57 @@ typedef __be64 xfs_bmbt_ptr_t, xfs_bmdr_ptr_t;
  * with the crc feature bit, and all accesses to them must be conditional on
  * that flag.
  */
+/* short form block header */
+struct xfs_btree_block_shdr {
+       __be32          bb_leftsib;
+       __be32          bb_rightsib;
+
+       __be64          bb_blkno;
+       __be64          bb_lsn;
+       uuid_t          bb_uuid;
+       __be32          bb_owner;
+       __le32          bb_crc;
+};
+
+/* long form block header */
+struct xfs_btree_block_lhdr {
+       __be64          bb_leftsib;
+       __be64          bb_rightsib;
+
+       __be64          bb_blkno;
+       __be64          bb_lsn;
+       uuid_t          bb_uuid;
+       __be64          bb_owner;
+       __le32          bb_crc;
+       __be32          bb_pad; /* padding for alignment */
+};
+
 struct xfs_btree_block {
        __be32          bb_magic;       /* magic number for block type */
        __be16          bb_level;       /* 0 is a leaf */
        __be16          bb_numrecs;     /* current # of data records */
        union {
-               struct {
-                       __be32          bb_leftsib;
-                       __be32          bb_rightsib;
-
-                       __be64          bb_blkno;
-                       __be64          bb_lsn;
-                       uuid_t          bb_uuid;
-                       __be32          bb_owner;
-                       __le32          bb_crc;
-               } s;                    /* short form pointers */
-               struct  {
-                       __be64          bb_leftsib;
-                       __be64          bb_rightsib;
-
-                       __be64          bb_blkno;
-                       __be64          bb_lsn;
-                       uuid_t          bb_uuid;
-                       __be64          bb_owner;
-                       __le32          bb_crc;
-                       __be32          bb_pad; /* padding for alignment */
-               } l;                    /* long form pointers */
+               struct xfs_btree_block_shdr s;
+               struct xfs_btree_block_lhdr l;
        } bb_u;                         /* rest */
 };
 
-#define XFS_BTREE_SBLOCK_LEN   16      /* size of a short form block */
-#define XFS_BTREE_LBLOCK_LEN   24      /* size of a long form block */
+/* size of a short form block */
+#define XFS_BTREE_SBLOCK_LEN \
+       (offsetof(struct xfs_btree_block, bb_u) + \
+        offsetof(struct xfs_btree_block_shdr, bb_blkno))
+/* size of a long form block */
+#define XFS_BTREE_LBLOCK_LEN \
+       (offsetof(struct xfs_btree_block, bb_u) + \
+        offsetof(struct xfs_btree_block_lhdr, bb_blkno))
 
 /* sizes of CRC enabled btree blocks */
-#define XFS_BTREE_SBLOCK_CRC_LEN       (XFS_BTREE_SBLOCK_LEN + 40)
-#define XFS_BTREE_LBLOCK_CRC_LEN       (XFS_BTREE_LBLOCK_LEN + 48)
+#define XFS_BTREE_SBLOCK_CRC_LEN \
+       (offsetof(struct xfs_btree_block, bb_u) + \
+        sizeof(struct xfs_btree_block_shdr))
+#define XFS_BTREE_LBLOCK_CRC_LEN \
+       (offsetof(struct xfs_btree_block, bb_u) + \
+        sizeof(struct xfs_btree_block_lhdr))
 
 #define XFS_BTREE_SBLOCK_CRC_OFF \
        offsetof(struct xfs_btree_block, bb_u.s.bb_crc)

diff --git a/fs/xfs/xfs_ondisk.h b/fs/xfs/xfs_ondisk.h
index 184c44effdd5a3bd107d1369c9b2873367951980..20a0d266964b07625100e8dfb189d64cd7a1026a 100644 (file)
--- a/fs/xfs/xfs_ondisk.h
+++ b/fs/xfs/xfs_ondisk.h
@@ -34,6 +34,8 @@ xfs_check_ondisk_structs(void)
        XFS_CHECK_STRUCT_SIZE(struct xfs_bmbt_key,              8);
        XFS_CHECK_STRUCT_SIZE(struct xfs_bmbt_rec,              16);
        XFS_CHECK_STRUCT_SIZE(struct xfs_bmdr_block,            4);
+       XFS_CHECK_STRUCT_SIZE(struct xfs_btree_block_shdr,      48);
+       XFS_CHECK_STRUCT_SIZE(struct xfs_btree_block_lhdr,      64);
        XFS_CHECK_STRUCT_SIZE(struct xfs_btree_block,           72);
        XFS_CHECK_STRUCT_SIZE(struct xfs_dinode,                176);
        XFS_CHECK_STRUCT_SIZE(struct xfs_disk_dquot,            104);