On Tue, 2007-09-25 at 14:33 +0530, Aneesh Kumar K.V wrote:
> ext4 file system layout contain different split members
> like bg_block_bitmap and bg_block_bitmap_hi. Introduce
> data type le32_t and le16_t to be used as the type of
> these split members. This prevents these members frome
> being accessed directly. Accesing them directly gives
> a compiler warning. This helps in catching some BUGS
> due to direct partial access of these split fields.
Ugh. I don't like this typedef at all. It just makes the data type more
confusing.
Why not just change the name of bg_block_bitmap to something like
bg_block_bitmap_lo or _bg_block_bitmap? It should be clear from the
name that it shouldn't be used without careful consideration.
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
> ---
> fs/ext4/super.c | 8 ++++----
> include/linux/ext4_fs.h | 4 ++--
> include/linux/ext4_fs_i.h | 4 ++++
> 3 files changed, 10 insertions(+), 6 deletions(-)
>
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index d035653..c8f8e4d 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -70,9 +70,9 @@ static void ext4_write_super_lockfs(struct super_block *sb);
> ext4_fsblk_t ext4_block_bitmap(struct super_block *sb,
> struct ext4_group_desc *bg)
> {
> - return le32_to_cpu(bg->bg_block_bitmap) |
> + return le32_to_cpu(bg->bg_block_bitmap.value) |
> (EXT4_DESC_SIZE(sb) >= EXT4_MIN_DESC_SIZE_64BIT ?
> - (ext4_fsblk_t)le32_to_cpu(bg->bg_block_bitmap_hi) << 32 : 0);
> + (ext4_fsblk_t)le32_to_cpu(bg->bg_block_bitmap_hi.value) << 32 : 0);
> }
>
> ext4_fsblk_t ext4_inode_bitmap(struct super_block *sb,
> @@ -94,9 +94,9 @@ ext4_fsblk_t ext4_inode_table(struct super_block *sb,
> void ext4_block_bitmap_set(struct super_block *sb,
> struct ext4_group_desc *bg, ext4_fsblk_t blk)
> {
> - bg->bg_block_bitmap = cpu_to_le32((u32)blk);
> + bg->bg_block_bitmap.value = cpu_to_le32((u32)blk);
> if (EXT4_DESC_SIZE(sb) >= EXT4_MIN_DESC_SIZE_64BIT)
> - bg->bg_block_bitmap_hi = cpu_to_le32(blk >> 32);
> + bg->bg_block_bitmap_hi.value = cpu_to_le32(blk >> 32);
> }
>
> void ext4_inode_bitmap_set(struct super_block *sb,
> diff --git a/include/linux/ext4_fs.h b/include/linux/ext4_fs.h
> index 046a6a7..4494f8e 100644
> --- a/include/linux/ext4_fs.h
> +++ b/include/linux/ext4_fs.h
> @@ -150,7 +150,7 @@ struct ext4_allocation_request {
> */
> struct ext4_group_desc
> {
> - __le32 bg_block_bitmap; /* Blocks bitmap block */
> + le32_t bg_block_bitmap; /* Blocks bitmap block */
> __le32 bg_inode_bitmap; /* Inodes bitmap block */
> __le32 bg_inode_table; /* Inodes table block */
> __le16 bg_free_blocks_count; /* Free blocks count */
> @@ -160,7 +160,7 @@ struct ext4_group_desc
> __u32 bg_reserved[2]; /* Likely block/inode bitmap checksum */
> __le16 bg_itable_unused; /* Unused inodes count */
> __le16 bg_checksum; /* crc16(sb_uuid+group+desc) */
> - __le32 bg_block_bitmap_hi; /* Blocks bitmap block MSB */
> + le32_t bg_block_bitmap_hi; /* Blocks bitmap block MSB */
> __le32 bg_inode_bitmap_hi; /* Inodes bitmap block MSB */
> __le32 bg_inode_table_hi; /* Inodes table block MSB */
> };
> diff --git a/include/linux/ext4_fs_i.h b/include/linux/ext4_fs_i.h
> index 22ba80e..d7eb271 100644
> --- a/include/linux/ext4_fs_i.h
> +++ b/include/linux/ext4_fs_i.h
> @@ -27,6 +27,10 @@ typedef int ext4_grpblk_t;
> /* data type for filesystem-wide blocks number */
> typedef unsigned long long ext4_fsblk_t;
>
> +/* data type to carry split 64 and 48 bits */
> +typedef struct { __le16 value; } le16_t;
> +typedef struct { __le32 value; } le32_t;
> +
> struct ext4_reserve_window {
> ext4_fsblk_t _rsv_start; /* First byte reserved */
> ext4_fsblk_t _rsv_end; /* Last byte reserved or 0 */
--
David Kleikamp
IBM Linux Technology Center
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