On Mon, Dec 19, 2016 at 11:13 PM, Darrick J. Wong
<darrick.wong@xxxxxxxxxx> wrote:
> 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?
>
sure.
> 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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