[RFC][PATCH v2 09/10] nilfs2: use common file type conversion

[Phillip Potter <phil@philpotter.co.uk>]

Deduplicate the nilfs2 file type conversion implementation.

Original patch by Amir Goldstein.

v2:
- Compile-time checks added by Phillip Potter to make
  sure the NILFS_FT_x enum values stay same as FT_x values

v1:
- Initial implementation

Signed-off-by: Phillip Potter <phil@philpotter.co.uk>
---
 fs/nilfs2/dir.c                    | 54 +++++++++++-------------------
 include/uapi/linux/nilfs2_ondisk.h |  1 +
 2 files changed, 20 insertions(+), 35 deletions(-)

diff --git a/fs/nilfs2/dir.c b/fs/nilfs2/dir.c
index 81394e22d0a0..168238278d24 100644
--- a/fs/nilfs2/dir.c
+++ b/fs/nilfs2/dir.c
@@ -229,35 +229,25 @@ static struct nilfs_dir_entry *nilfs_next_entry(struct nilfs_dir_entry *p)
 					  nilfs_rec_len_from_disk(p->rec_len));
 }
 
-static unsigned char
-nilfs_filetype_table[NILFS_FT_MAX] = {
-	[NILFS_FT_UNKNOWN]	= DT_UNKNOWN,
-	[NILFS_FT_REG_FILE]	= DT_REG,
-	[NILFS_FT_DIR]		= DT_DIR,
-	[NILFS_FT_CHRDEV]	= DT_CHR,
-	[NILFS_FT_BLKDEV]	= DT_BLK,
-	[NILFS_FT_FIFO]		= DT_FIFO,
-	[NILFS_FT_SOCK]		= DT_SOCK,
-	[NILFS_FT_SYMLINK]	= DT_LNK,
-};
-
-#define S_SHIFT 12
-static unsigned char
-nilfs_type_by_mode[S_IFMT >> S_SHIFT] = {
-	[S_IFREG >> S_SHIFT]	= NILFS_FT_REG_FILE,
-	[S_IFDIR >> S_SHIFT]	= NILFS_FT_DIR,
-	[S_IFCHR >> S_SHIFT]	= NILFS_FT_CHRDEV,
-	[S_IFBLK >> S_SHIFT]	= NILFS_FT_BLKDEV,
-	[S_IFIFO >> S_SHIFT]	= NILFS_FT_FIFO,
-	[S_IFSOCK >> S_SHIFT]	= NILFS_FT_SOCK,
-	[S_IFLNK >> S_SHIFT]	= NILFS_FT_SYMLINK,
-};
-
 static void nilfs_set_de_type(struct nilfs_dir_entry *de, struct inode *inode)
 {
-	umode_t mode = inode->i_mode;
-
-	de->file_type = nilfs_type_by_mode[(mode & S_IFMT)>>S_SHIFT];
+	/*
+	 * compile-time asserts that generic FT_x types
+	 * still match NILFS_FT_x types - no need to list
+	 * in other functions as well as build will
+	 * fail either way
+	 */
+	BUILD_BUG_ON(NILFS_FT_UNKNOWN != FT_UNKNOWN);
+	BUILD_BUG_ON(NILFS_FT_REG_FILE != FT_REG_FILE);
+	BUILD_BUG_ON(NILFS_FT_DIR != FT_DIR);
+	BUILD_BUG_ON(NILFS_FT_CHRDEV != FT_CHRDEV);
+	BUILD_BUG_ON(NILFS_FT_BLKDEV != FT_BLKDEV);
+	BUILD_BUG_ON(NILFS_FT_FIFO != FT_FIFO);
+	BUILD_BUG_ON(NILFS_FT_SOCK != FT_SOCK);
+	BUILD_BUG_ON(NILFS_FT_SYMLINK != FT_SYMLINK);
+	BUILD_BUG_ON(NILFS_FT_MAX != FT_MAX);
+
+	de->file_type = fs_umode_to_ftype(inode->i_mode);
 }
 
 static int nilfs_readdir(struct file *file, struct dir_context *ctx)
@@ -293,15 +283,9 @@ static int nilfs_readdir(struct file *file, struct dir_context *ctx)
 				return -EIO;
 			}
 			if (de->inode) {
-				unsigned char t;
-
-				if (de->file_type < NILFS_FT_MAX)
-					t = nilfs_filetype_table[de->file_type];
-				else
-					t = DT_UNKNOWN;
-
 				if (!dir_emit(ctx, de->name, de->name_len,
-						le64_to_cpu(de->inode), t)) {
+						le64_to_cpu(de->inode),
+						fs_dtype(de->file_type))) {
 					nilfs_put_page(page);
 					return 0;
 				}
diff --git a/include/uapi/linux/nilfs2_ondisk.h b/include/uapi/linux/nilfs2_ondisk.h
index a7e66ab11d1d..90362b1957f1 100644
--- a/include/uapi/linux/nilfs2_ondisk.h
+++ b/include/uapi/linux/nilfs2_ondisk.h
@@ -309,6 +309,7 @@ struct nilfs_dir_entry {
 /*
  * NILFS directory file types.  Only the low 3 bits are used.  The
  * other bits are reserved for now.
+ * Values should match common file type values in file_type.h.
  */
 enum {
 	NILFS_FT_UNKNOWN,
-- 
2.17.2