From: Andrew Morton The on-disk media specification field in FAT is only 8-bits, so testing for <=0xff is pointless, and can generate a "comparison is always true due to limited range of data type" warning. While we're there, convert FAT_VALID_MEDIA() into a C function - the present implementation is buggy: it generates either one or two references to its argument. Cc: Frank Seidel Cc: OGAWA Hirofumi Signed-off-by: Andrew Morton --- fs/fat/inode.c | 2 +- include/linux/msdos_fs.h | 6 +++++- 2 files changed, 6 insertions(+), 2 deletions(-) diff -puN include/linux/msdos_fs.h~fat_valid_media-remove-pointless-test include/linux/msdos_fs.h --- a/include/linux/msdos_fs.h~fat_valid_media-remove-pointless-test +++ a/include/linux/msdos_fs.h @@ -58,7 +58,11 @@ #define MSDOS_DOTDOT ".. " /* "..", padded to MSDOS_NAME chars */ /* media of boot sector */ -#define FAT_VALID_MEDIA(x) ((0xF8 <= (x) && (x) <= 0xFF) || (x) == 0xF0) +static inline int fat_valid_media(u8 media) +{ + return 0xf8 <= media || media == 0xf0; +} + #define FAT_FIRST_ENT(s, x) ((MSDOS_SB(s)->fat_bits == 32 ? 0x0FFFFF00 : \ MSDOS_SB(s)->fat_bits == 16 ? 0xFF00 : 0xF00) | (x)) diff -puN fs/fat/inode.c~fat_valid_media-remove-pointless-test fs/fat/inode.c --- a/fs/fat/inode.c~fat_valid_media-remove-pointless-test +++ a/fs/fat/inode.c @@ -1208,7 +1208,7 @@ int fat_fill_super(struct super_block *s */ media = b->media; - if (!FAT_VALID_MEDIA(media)) { + if (!fat_valid_media(media)) { if (!silent) printk(KERN_ERR "FAT: invalid media value (0x%02x)\n", media); _