The FS_IOC_GETFLAGS, FS_IOC_SETFLAGS, FS_IOC_GETVERSION and FS_IOC_SETVERSION ioctls are declared for historical reasons with a long argument, while in practice they take an int argument. This is unfortunately not possible to fix that without breaking the kernel ABI.
However good programmers actually lookup for the argument type of these ioctls in <fs/linux.h> and end-up using a long. This breaks on 64-bit big endian machines. Instead of letting the same "mistake" to be done again and again, add an explanation to <fs/linux.h> so that people use the correct argument type in their code. Also add a small comment on the same line while staying within 80 characters so that the issue appears when doing a grep on this file. Cc: Alexander Viro <[email protected]> Cc: Christoph Hellwig <[email protected]> Cc: Theodore Ts'o <[email protected]> Cc: [email protected] Signed-off-by: Aurelien Jarno <[email protected]> --- include/uapi/linux/fs.h | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h index 6c28b61..baeb803 100644 --- a/include/uapi/linux/fs.h +++ b/include/uapi/linux/fs.h @@ -154,10 +154,16 @@ struct inodes_stat_t { #define FITHAW _IOWR('X', 120, int) /* Thaw */ #define FITRIM _IOWR('X', 121, struct fstrim_range) /* Trim */ -#define FS_IOC_GETFLAGS _IOR('f', 1, long) -#define FS_IOC_SETFLAGS _IOW('f', 2, long) -#define FS_IOC_GETVERSION _IOR('v', 1, long) -#define FS_IOC_SETVERSION _IOW('v', 2, long) +/* + * WARNING: The next four following ioctls actually take an int argument + * despite their definition. This is important to support 64-bit big-endian + * machines. + */ +#define FS_IOC_GETFLAGS _IOR('f', 1, long) /* should be int */ +#define FS_IOC_SETFLAGS _IOW('f', 2, long) /* should be int */ +#define FS_IOC_GETVERSION _IOR('v', 1, long) /* should be int */ +#define FS_IOC_SETVERSION _IOW('v', 2, long) /* should be int */ + #define FS_IOC_FIEMAP _IOWR('f', 11, struct fiemap) #define FS_IOC32_GETFLAGS _IOR('f', 1, int) #define FS_IOC32_SETFLAGS _IOW('f', 2, int) -- 1.8.4.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
