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

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

Deduplicate the btrfs file type conversion implementation.

Original patch by Amir Goldstein.

v2:
- Rebased against Linux 4.19 by Phillip Potter
- Compile-time checks added by Phillip Potter to make
  sure the BTRFS_FT_x enum values stay same as FT_x values

v1:
- Initial implementation

Signed-off-by: Phillip Potter <phil@philpotter.co.uk>
---
 fs/btrfs/btrfs_inode.h          |  2 --
 fs/btrfs/delayed-inode.c        |  2 +-
 fs/btrfs/inode.c                | 35 +++++++++++++++++----------------
 include/uapi/linux/btrfs_tree.h |  2 ++
 4 files changed, 21 insertions(+), 20 deletions(-)

diff --git a/fs/btrfs/btrfs_inode.h b/fs/btrfs/btrfs_inode.h
index 1343ac57b438..c7c6db6b4a35 100644
--- a/fs/btrfs/btrfs_inode.h
+++ b/fs/btrfs/btrfs_inode.h
@@ -196,8 +196,6 @@ struct btrfs_inode {
 	struct inode vfs_inode;
 };
 
-extern unsigned char btrfs_filetype_table[];
-
 static inline struct btrfs_inode *BTRFS_I(const struct inode *inode)
 {
 	return container_of(inode, struct btrfs_inode, vfs_inode);
diff --git a/fs/btrfs/delayed-inode.c b/fs/btrfs/delayed-inode.c
index f51b509f2d9b..c1da34e3a775 100644
--- a/fs/btrfs/delayed-inode.c
+++ b/fs/btrfs/delayed-inode.c
@@ -1691,7 +1691,7 @@ int btrfs_readdir_delayed_dir_index(struct dir_context *ctx,
 		name = (char *)(di + 1);
 		name_len = btrfs_stack_dir_name_len(di);
 
-		d_type = btrfs_filetype_table[di->type];
+		d_type = fs_dtype(di->type);
 		btrfs_disk_key_to_cpu(&location, &di->location);
 
 		over = !dir_emit(ctx, name, name_len,
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 3ea5339603cf..4cbdcba4799a 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -73,17 +73,6 @@ struct kmem_cache *btrfs_trans_handle_cachep;
 struct kmem_cache *btrfs_path_cachep;
 struct kmem_cache *btrfs_free_space_cachep;
 
-#define S_SHIFT 12
-static const unsigned char btrfs_type_by_mode[S_IFMT >> S_SHIFT] = {
-	[S_IFREG >> S_SHIFT]	= BTRFS_FT_REG_FILE,
-	[S_IFDIR >> S_SHIFT]	= BTRFS_FT_DIR,
-	[S_IFCHR >> S_SHIFT]	= BTRFS_FT_CHRDEV,
-	[S_IFBLK >> S_SHIFT]	= BTRFS_FT_BLKDEV,
-	[S_IFIFO >> S_SHIFT]	= BTRFS_FT_FIFO,
-	[S_IFSOCK >> S_SHIFT]	= BTRFS_FT_SOCK,
-	[S_IFLNK >> S_SHIFT]	= BTRFS_FT_SYMLINK,
-};
-
 static int btrfs_setsize(struct inode *inode, struct iattr *attr);
 static int btrfs_truncate(struct inode *inode, bool skip_writeback);
 static int btrfs_finish_ordered_io(struct btrfs_ordered_extent *ordered_extent);
@@ -5803,10 +5792,6 @@ static struct dentry *btrfs_lookup(struct inode *dir, struct dentry *dentry,
 	return d_splice_alias(inode, dentry);
 }
 
-unsigned char btrfs_filetype_table[] = {
-	DT_UNKNOWN, DT_REG, DT_DIR, DT_CHR, DT_BLK, DT_FIFO, DT_SOCK, DT_LNK
-};
-
 /*
  * All this infrastructure exists because dir_emit can fault, and we are holding
  * the tree lock when doing readdir.  For now just allocate a buffer and copy
@@ -5945,7 +5930,23 @@ static int btrfs_real_readdir(struct file *file, struct dir_context *ctx)
 		name_ptr = (char *)(entry + 1);
 		read_extent_buffer(leaf, name_ptr, (unsigned long)(di + 1),
 				   name_len);
-		put_unaligned(btrfs_filetype_table[btrfs_dir_type(leaf, di)],
+
+		/*
+		 * compile-time asserts that generic FT_x types
+		 * still match BTRFS_FT_x types - no need to list
+		 * in other functions as well as build will
+		 * fail either way
+		 */
+		BUILD_BUG_ON(BTRFS_FT_UNKNOWN != FT_UNKNOWN);
+		BUILD_BUG_ON(BTRFS_FT_REG_FILE != FT_REG_FILE);
+		BUILD_BUG_ON(BTRFS_FT_DIR != FT_DIR);
+		BUILD_BUG_ON(BTRFS_FT_CHRDEV != FT_CHRDEV);
+		BUILD_BUG_ON(BTRFS_FT_BLKDEV != FT_BLKDEV);
+		BUILD_BUG_ON(BTRFS_FT_FIFO != FT_FIFO);
+		BUILD_BUG_ON(BTRFS_FT_SOCK != FT_SOCK);
+		BUILD_BUG_ON(BTRFS_FT_SYMLINK != FT_SYMLINK);
+
+		put_unaligned(fs_dtype(btrfs_dir_type(leaf, di)),
 				&entry->type);
 		btrfs_dir_item_key_to_cpu(leaf, di, &location);
 		put_unaligned(location.objectid, &entry->ino);
@@ -6350,7 +6351,7 @@ static struct inode *btrfs_new_inode(struct btrfs_trans_handle *trans,
 
 static inline u8 btrfs_inode_type(struct inode *inode)
 {
-	return btrfs_type_by_mode[(inode->i_mode & S_IFMT) >> S_SHIFT];
+	return fs_umode_to_ftype(inode->i_mode);
 }
 
 /*
diff --git a/include/uapi/linux/btrfs_tree.h b/include/uapi/linux/btrfs_tree.h
index aff1356c2bb8..5747cffa09fa 100644
--- a/include/uapi/linux/btrfs_tree.h
+++ b/include/uapi/linux/btrfs_tree.h
@@ -307,6 +307,8 @@
  *
  * Used by:
  * struct btrfs_dir_item.type
+ *
+ * Values 0..7 should match common file type values in file_type.h.
  */
 #define BTRFS_FT_UNKNOWN	0
 #define BTRFS_FT_REG_FILE	1
-- 
2.17.2