f2fs: add annotation for space utilization of regular/inline dentry

Add annotation to let us know more clearly about space utilization
information of regular dentry and inline dentry.

Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

diff --git a/include/linux/f2fs_fs.h b/include/linux/f2fs_fs.h
index 920408a21ffdcfeb0c7d2239d5c4478dcf4bef3e..25c6324a0dd04a9be333fcd22e9b4ffdda9c0796 100644 (file)
--- a/include/linux/f2fs_fs.h
+++ b/include/linux/f2fs_fs.h
@@ -417,15 +417,25 @@ typedef __le32    f2fs_hash_t;
 
 #define GET_DENTRY_SLOTS(x)    ((x + F2FS_SLOT_LEN - 1) >> F2FS_SLOT_LEN_BITS)
 
-/* the number of dentry in a block */
-#define NR_DENTRY_IN_BLOCK     214
-
 /* MAX level for dir lookup */
 #define MAX_DIR_HASH_DEPTH     63
 
 /* MAX buckets in one level of dir */
 #define MAX_DIR_BUCKETS                (1 << ((MAX_DIR_HASH_DEPTH / 2) - 1))
 
+/*
+ * space utilization of regular dentry and inline dentry
+ *             regular dentry                  inline dentry
+ * bitmap      1 * 27 = 27                     1 * 23 = 23
+ * reserved    1 * 3 = 3                       1 * 7 = 7
+ * dentry      11 * 214 = 2354                 11 * 182 = 2002
+ * filename    8 * 214 = 1712                  8 * 182 = 1456
+ * total       4096                            3488
+ *
+ * Note: there are more reserved space in inline dentry than in regular
+ * dentry, when converting inline dentry we should handle this carefully.
+ */
+#define NR_DENTRY_IN_BLOCK     214     /* the number of dentry in a block */
 #define SIZE_OF_DIR_ENTRY      11      /* by byte */
 #define SIZE_OF_DENTRY_BITMAP  ((NR_DENTRY_IN_BLOCK + BITS_PER_BYTE - 1) / \
                                        BITS_PER_BYTE)