On Mon, Dec 19, 2016 at 10:10:58PM +0200, Amir Goldstein wrote:
> 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,
[FT_UNKNOWN] = DT_UNKNOWN, etc?
It's not strictly necessary but it makes the mapping more explicit.
--D
> + 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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