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>
Signed-off-by: Phillip Potter <phil@xxxxxxxxxxxxxxxx>
---
MAINTAINERS | 1 +
fs/Makefile | 3 +-
fs/fs_types.c | 105 +++++++++++++++++++++++++++++++++++++++
include/linux/fs.h | 17 +------
include/linux/fs_types.h | 73 +++++++++++++++++++++++++++
5 files changed, 182 insertions(+), 17 deletions(-)
create mode 100644 fs/fs_types.c
create mode 100644 include/linux/fs_types.h
diff --git a/MAINTAINERS b/MAINTAINERS
index bd702ad56c7f..9491208c115f 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -5711,6 +5711,7 @@ L: linux-fsdevel@xxxxxxxxxxxxxxx
S: Maintained
F: fs/*
F: include/linux/fs.h
+F: include/linux/fs_types.h
F: include/uapi/linux/fs.h
FINTEK F75375S HARDWARE MONITOR AND FAN CONTROLLER DRIVER
diff --git a/fs/Makefile b/fs/Makefile
index 293733f61594..23fcd8c164a3 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -12,7 +12,8 @@ obj-y := open.o read_write.o file_table.o super.o \
attr.o bad_inode.o file.o filesystems.o namespace.o \
seq_file.o xattr.o libfs.o fs-writeback.o \
pnode.o splice.o sync.o utimes.o d_path.o \
- stack.o fs_struct.o statfs.o fs_pin.o nsfs.o
+ stack.o fs_struct.o statfs.o fs_pin.o nsfs.o \
+ fs_types.o
ifeq ($(CONFIG_BLOCK),y)
obj-y += buffer.o block_dev.o direct-io.o mpage.o
diff --git a/fs/fs_types.c b/fs/fs_types.c
new file mode 100644
index 000000000000..6fc57f4b1dcb
--- /dev/null
+++ b/fs/fs_types.c
@@ -0,0 +1,105 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/fs.h>
+#include <linux/export.h>
+
+/*
+ * fs on-disk file type to dirent file type conversion
+ */
+static unsigned char fs_dtype_by_ftype[FT_MAX] = {
+ [FT_UNKNOWN] = DT_UNKNOWN,
+ [FT_REG_FILE] = DT_REG,
+ [FT_DIR] = DT_DIR,
+ [FT_CHRDEV] = DT_CHR,
+ [FT_BLKDEV] = DT_BLK,
+ [FT_FIFO] = DT_FIFO,
+ [FT_SOCK] = DT_SOCK,
+ [FT_SYMLINK] = DT_LNK
+};
+
+/**
+ * fs_ftype_to_dtype() - fs on-disk file type to dirent type.
+ * @filetype: The on-disk file type to convert.
+ *
+ * This function converts the on-disk file type value (FT_*) to the directory
+ * entry type (DT_*).
+ *
+ * Context: Any context.
+ * Return:
+ * * DT_UNKNOWN - Unknown type
+ * * DT_FIFO - FIFO
+ * * DT_CHR - Character device
+ * * DT_DIR - Directory
+ * * DT_BLK - Block device
+ * * DT_REG - Regular file
+ * * DT_LNK - Symbolic link
+ * * DT_SOCK - Local-domain socket
+ */
+unsigned char fs_ftype_to_dtype(unsigned int filetype)
+{
+ if (filetype >= FT_MAX)
+ return DT_UNKNOWN;
+
+ return fs_dtype_by_ftype[filetype];
+}
+EXPORT_SYMBOL_GPL(fs_ftype_to_dtype);
+
+/*
+ * 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,
+};
+
+/**
+ * fs_umode_to_ftype() - file mode to on-disk file type.
+ * @mode: The file mode to convert.
+ *
+ * This function converts the file mode value to the on-disk file type (FT_*).
+ *
+ * Context: Any context.
+ * Return:
+ * * FT_UNKNOWN - Unknown type
+ * * FT_REG_FILE - Regular file
+ * * FT_DIR - Directory
+ * * FT_CHRDEV - Character device
+ * * FT_BLKDEV - Block device
+ * * FT_FIFO - FIFO
+ * * FT_SOCK - Local-domain socket
+ * * FT_SYMLINK - Symbolic link
+ */
+unsigned char fs_umode_to_ftype(umode_t mode)
+{
+ return fs_ftype_by_dtype[S_DT(mode)];
+}
+EXPORT_SYMBOL_GPL(fs_umode_to_ftype);
+
+/**
+ * fs_umode_to_dtype() - file mode to dirent file type.
+ * @mode: The file mode to convert.
+ *
+ * This function converts the file mode value to the directory
+ * entry type (DT_*).
+ *
+ * Context: Any context.
+ * Return:
+ * * DT_UNKNOWN - Unknown type
+ * * DT_FIFO - FIFO
+ * * DT_CHR - Character device
+ * * DT_DIR - Directory
+ * * DT_BLK - Block device
+ * * DT_REG - Regular file
+ * * DT_LNK - Symbolic link
+ * * DT_SOCK - Local-domain socket
+ */
+unsigned char fs_umode_to_dtype(umode_t mode)
+{
+ return fs_ftype_to_dtype(fs_umode_to_ftype(mode));
+}
+EXPORT_SYMBOL_GPL(fs_umode_to_dtype);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 897eae8faee1..1dc76c9ea309 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -37,6 +37,7 @@
#include <linux/uuid.h>
#include <linux/errseq.h>
#include <linux/ioprio.h>
+#include <linux/fs_types.h>
#include <asm/byteorder.h>
#include <uapi/linux/fs.h>
@@ -1663,22 +1664,6 @@ int fiemap_fill_next_extent(struct fiemap_extent_info *info, u64 logical,
u64 phys, u64 len, u32 flags);
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.
diff --git a/include/linux/fs_types.h b/include/linux/fs_types.h
new file mode 100644
index 000000000000..7d147b2f1702
--- /dev/null
+++ b/include/linux/fs_types.h
@@ -0,0 +1,73 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_FS_TYPES_H
+#define _LINUX_FS_TYPES_H
+
+/*
+ * This is a header for the 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.
+ *
+ * It is important to note that the definitions in this
+ * header MUST NOT change. This would break both the
+ * userspace ABI and the on-disk format of filesystems
+ * using this code.
+ *
+ * All those file systems can use this generic code for the
+ * conversions.
+ */
+
+/*
+ * 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 S_DT_MASK (S_IFMT >> S_DT_SHIFT)
+
+/* these are defined by POSIX and also present in glibc's dirent.h */
+#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
+
+#define DT_MAX (S_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
+
+/*
+ * declarations for helper functions, accompanying implementation
+ * is in fs/fs_types.c
+ */
+extern unsigned char fs_ftype_to_dtype(unsigned int filetype);
+extern unsigned char fs_umode_to_ftype(umode_t mode);
+extern unsigned char fs_umode_to_dtype(umode_t mode);
+
+#endif
--
2.17.2
