From bbe7449e2599b58cf7b995461e2189998111f907 Mon Sep 17 00:00:00 2001 From: Phillip Potter Date: Mon, 21 Jan 2019 00:54:27 +0000 Subject: fs: common implementation of file type 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 Signed-off-by: Phillip Potter Signed-off-by: Jan Kara --- include/linux/fs_types.h | 75 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 75 insertions(+) create mode 100644 include/linux/fs_types.h (limited to 'include/linux/fs_types.h') diff --git a/include/linux/fs_types.h b/include/linux/fs_types.h new file mode 100644 index 000000000000..54816791196f --- /dev/null +++ b/include/linux/fs_types.h @@ -0,0 +1,75 @@ +/* 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. + * These definitions are shared and used by multiple filesystems, + * and MUST NOT change under any circumstances. + * + * 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 -- cgit v1.2.3-59-g8ed1b