ext4: drop ec_type from the ext4_ext_cache structure

We can encode the ec_type information by using ee_len == 0 to denote
EXT4_EXT_CACHE_NO, ee_start == 0 to denote EXT4_EXT_CACHE_GAP, and if
neither is true, then the cache type must be EXT4_EXT_CACHE_EXTENT.
This allows us to reduce the size of ext4_ext_inode by another 8
bytes.  (ec_type is 4 bytes, plus another 4 bytes of padding)

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

diff --git a/fs/ext4/ext4_extents.h b/fs/ext4/ext4_extents.h
index dfdda17..2e29abb 100644
--- a/fs/ext4/ext4_extents.h
+++ b/fs/ext4/ext4_extents.h
@@ -119,10 +119,6 @@
  * structure for external API
  */
 
-#define EXT4_EXT_CACHE_NO	0
-#define EXT4_EXT_CACHE_GAP	1
-#define EXT4_EXT_CACHE_EXTENT	2
-
 /*
  * to be called by ext4_ext_walk_space()
  * negative retcode - error
@@ -197,7 +193,7 @@
 static inline void
 ext4_ext_invalidate_cache(struct inode *inode)
 {
-	EXT4_I(inode)->i_cached_extent.ec_type = EXT4_EXT_CACHE_NO;
+	EXT4_I(inode)->i_cached_extent.ec_len = 0;
 }
 
 static inline void ext4_ext_mark_uninitialized(struct ext4_extent *ext)