diff options
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/ext4_fs_extents.h | 31 |
1 files changed, 27 insertions, 4 deletions
diff --git a/include/linux/ext4_fs_extents.h b/include/linux/ext4_fs_extents.h index edf49ec89ea..81406f3655d 100644 --- a/include/linux/ext4_fs_extents.h +++ b/include/linux/ext4_fs_extents.h @@ -141,7 +141,25 @@ typedef int (*ext_prepare_callback)(struct inode *, struct ext4_ext_path *, #define EXT_MAX_BLOCK 0xffffffff -#define EXT_MAX_LEN ((1UL << 15) - 1) +/* + * EXT_INIT_MAX_LEN is the maximum number of blocks we can have in an + * initialized extent. This is 2^15 and not (2^16 - 1), since we use the + * MSB of ee_len field in the extent datastructure to signify if this + * particular extent is an initialized extent or an uninitialized (i.e. + * preallocated). + * EXT_UNINIT_MAX_LEN is the maximum number of blocks we can have in an + * uninitialized extent. + * If ee_len is <= 0x8000, it is an initialized extent. Otherwise, it is an + * uninitialized one. In other words, if MSB of ee_len is set, it is an + * uninitialized extent with only one special scenario when ee_len = 0x8000. + * In this case we can not have an uninitialized extent of zero length and + * thus we make it as a special case of initialized extent with 0x8000 length. + * This way we get better extent-to-group alignment for initialized extents. + * Hence, the maximum number of blocks we can have in an *initialized* + * extent is 2^15 (32768) and in an *uninitialized* extent is 2^15-1 (32767). + */ +#define EXT_INIT_MAX_LEN (1UL << 15) +#define EXT_UNINIT_MAX_LEN (EXT_INIT_MAX_LEN - 1) #define EXT_FIRST_EXTENT(__hdr__) \ @@ -190,17 +208,22 @@ ext4_ext_invalidate_cache(struct inode *inode) static inline void ext4_ext_mark_uninitialized(struct ext4_extent *ext) { - ext->ee_len |= cpu_to_le16(0x8000); + /* We can not have an uninitialized extent of zero length! */ + BUG_ON((le16_to_cpu(ext->ee_len) & ~EXT_INIT_MAX_LEN) == 0); + ext->ee_len |= cpu_to_le16(EXT_INIT_MAX_LEN); } static inline int ext4_ext_is_uninitialized(struct ext4_extent *ext) { - return (int)(le16_to_cpu((ext)->ee_len) & 0x8000); + /* Extent with ee_len of 0x8000 is treated as an initialized extent */ + return (le16_to_cpu(ext->ee_len) > EXT_INIT_MAX_LEN); } static inline int ext4_ext_get_actual_len(struct ext4_extent *ext) { - return (int)(le16_to_cpu((ext)->ee_len) & 0x7FFF); + return (le16_to_cpu(ext->ee_len) <= EXT_INIT_MAX_LEN ? + le16_to_cpu(ext->ee_len) : + (le16_to_cpu(ext->ee_len) - EXT_INIT_MAX_LEN)); } extern int ext4_extent_tree_init(handle_t *, struct inode *); |