Many file systems use a copy&paste implementation
of dirent to on-disk file type conversions.
Create a common implementation to be used by file systems
with some useful conversion helpers to reduce open coded
file type conversions in file system code.
Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
---
include/linux/file_type.h | 107 ++++++++++++++++++++++++++++++++++++++++++++++
include/linux/fs.h | 17 +-------
2 files changed, 108 insertions(+), 16 deletions(-)
create mode 100644 include/linux/file_type.h
diff --git a/include/linux/file_type.h b/include/linux/file_type.h
new file mode 100644
index 0000000..03ee1a1
--- /dev/null
+++ b/include/linux/file_type.h
@@ -0,0 +1,107 @@
+#ifndef _LINUX_FILE_TYPE_H
+#define _LINUX_FILE_TYPE_H
+
+/*
+ * This is a common implementation of dirent to fs on-disk
+ * file type conversion. Although the fs on-disk bits are
+ * specific to every file system, in practice, many file systems
+ * use the exact same on-disk format to describe the lower 3
+ * file type bits that represent the 7 POSIX file types.
+ * All those file systems can use this generic code for the
+ * conversions:
+ * i_mode -> fs on-disk file type (ftype)
+ * fs on-disk file type (ftype) -> dirent file type (dtype)
+ * i_mode -> dirent file type (dtype)
+ */
+
+/*
+ * struct dirent file types
+ * exposed to user via getdents(2), readdir(3)
+ *
+ * These match bits 12..15 of stat.st_mode
+ * (ie "(i_mode >> 12) & 15").
+ */
+#define S_DT_SHIFT 12
+#define S_DT(mode) (((mode) & S_IFMT) >> S_DT_SHIFT)
+#define DT_MASK (S_IFMT >> S_DT_SHIFT)
+
+#define DT_UNKNOWN 0
+#define DT_FIFO S_DT(S_IFIFO) /* 1 */
+#define DT_CHR S_DT(S_IFCHR) /* 2 */
+#define DT_DIR S_DT(S_IFDIR) /* 4 */
+#define DT_BLK S_DT(S_IFBLK) /* 6 */
+#define DT_REG S_DT(S_IFREG) /* 8 */
+#define DT_LNK S_DT(S_IFLNK) /* 10 */
+#define DT_SOCK S_DT(S_IFSOCK) /* 12 */
+#define DT_WHT 14
+
+#define DT_MAX (DT_MASK + 1) /* 16 */
+
+/*
+ * fs on-disk file types.
+ * Only the low 3 bits are used for the POSIX file types.
+ * Other bits are reserved for fs private use.
+ *
+ * Note that no fs currently stores the whiteout type on-disk,
+ * so whiteout dirents are exposed to user as DT_CHR.
+ */
+#define FT_UNKNOWN 0
+#define FT_REG_FILE 1
+#define FT_DIR 2
+#define FT_CHRDEV 3
+#define FT_BLKDEV 4
+#define FT_FIFO 5
+#define FT_SOCK 6
+#define FT_SYMLINK 7
+
+#define FT_MAX 8
+
+/*
+ * fs on-disk file type to dirent file type conversion
+ */
+static unsigned char fs_dtype_by_ftype[] = {
+ DT_UNKNOWN,
+ DT_REG,
+ DT_DIR,
+ DT_CHR,
+ DT_BLK,
+ DT_FIFO,
+ DT_SOCK,
+ DT_LNK
+};
+
+static inline unsigned char fs_dtype(int filetype)
+{
+ if (filetype >= FT_MAX)
+ return DT_UNKNOWN;
+
+ return fs_dtype_by_ftype[filetype];
+}
+
+/*
+ * dirent file type to fs on-disk file type conversion
+ * Values not initialized explicitly are FT_UNKNOWN (0).
+ */
+static unsigned char fs_ftype_by_dtype[DT_MAX] = {
+ [DT_REG] = FT_REG_FILE,
+ [DT_DIR] = FT_DIR,
+ [DT_LNK] = FT_SYMLINK,
+ [DT_CHR] = FT_CHRDEV,
+ [DT_BLK] = FT_BLKDEV,
+ [DT_FIFO] = FT_FIFO,
+ [DT_SOCK] = FT_SOCK,
+};
+
+/* st_mode to fs on-disk file type conversion */
+static inline unsigned char fs_umode_to_ftype(umode_t mode)
+{
+ return fs_ftype_by_dtype[S_DT(mode)];
+}
+
+/* st_mode to dirent file type conversion */
+static inline unsigned char fs_umode_to_dtype(umode_t mode)
+{
+ return fs_dtype(fs_umode_to_ftype(mode));
+}
+
+#endif
diff --git a/include/linux/fs.h b/include/linux/fs.h
index e6e4146..8f1580d 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -31,6 +31,7 @@
#include <linux/workqueue.h>
#include <linux/percpu-rwsem.h>
#include <linux/delayed_call.h>
+#include <linux/file_type.h>
#include <asm/byteorder.h>
#include <uapi/linux/fs.h>
@@ -1582,22 +1583,6 @@ int fiemap_fill_next_extent(struct fiemap_extent_info *info, u64 logical,
int fiemap_check_flags(struct fiemap_extent_info *fieinfo, u32 fs_flags);
/*
- * File types
- *
- * NOTE! These match bits 12..15 of stat.st_mode
- * (ie "(i_mode >> 12) & 15").
- */
-#define DT_UNKNOWN 0
-#define DT_FIFO 1
-#define DT_CHR 2
-#define DT_DIR 4
-#define DT_BLK 6
-#define DT_REG 8
-#define DT_LNK 10
-#define DT_SOCK 12
-#define DT_WHT 14
-
-/*
* This is the "filldir" function type, used by readdir() to let
* the kernel specify what kind of dirent layout it wants to have.
* This allows the kernel to read directories into kernel space or
--
2.7.4
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