NAME_OFFSET macro

milind@arun:~/src/linux> egrep -rin "#define.*NAME_?OFFSET" .
./arch/alpha/kernel/osf_sys.c:95:#define NAME_OFFSET offsetof (struct osf_dirent, d_name)
./arch/mips/kernel/sysirix.c:1738:#define NAME_OFFSET32(de) ((int) ((de)->d_name - (char *) (de))) ./arch/mips/kernel/sysirix.c:1840:#define NAME_OFFSET64(de) ((int) ((de)->d_name - (char *) (de))) ./arch/parisc/hpux/fs.c:72:#define NAME_OFFSET(de) ((int) ((de)->d_name - (char __user *) (de))) ./arch/parisc/kernel/sys_parisc32.c:315:#define NAME_OFFSET(de) ((int) ((de)->d_name - (char __user *) (de))) ./arch/powerpc/kernel/sys_ppc32.c:57:#define NAME_OFFSET(de) ((int) ((de)->d_name - (char __user *) (de))) ./arch/sparc/kernel/sys_sunos.c:324:#define NAME_OFFSET(de) ((int) ((de)->d_name - (char __user *) (de))) ./arch/sparc64/kernel/sys_sunos32.c:275:#define NAME_OFFSET(de) ((int) ((de)->d_name - (char __user *) (de)))
./drivers/isdn/hardware/eicon/s_4bri.c:184:#define FPGA_NAME_OFFSET 0x10
./fs/compat.c:903:#define NAME_OFFSET(de) ((int) ((de)->d_name - (char __user *) (de))) ./fs/readdir.c:54:#define NAME_OFFSET(de) ((int) ((de)->d_name - (char __user *) (de))) ./include/linux/fuse.h:342:#define FUSE_NAME_OFFSET ((unsigned) ((struct fuse_dirent *) 0)->name)

just working out different options before putting it in kernel.h

as all the dirent structures have used the
same name for the d_name member,so we can use

#define NAME_OFFSET(dirent) ((int) ((dirent)->d_name - (char __user *) (dirent)))

but then it becomes binding on the future users
to maintain the same naming convention.

#define NAME_OFFSET(dirent,d_name) ((int) ((dirent)->d_name - (char __user *) (dirent)))

#define NAME_OFFSET(dirent,d_name) offsetof(struct dirent,d_name)

though ..the first one seem to be just fine

thoughts

Milind Arun Choudhary

Delete all instances of the macro. Replace all uses of it with offsetof(foo, name). You wouldn't wrap a simple sizeof in a macro like this, there's no reason to do so with offsetof except for ignorance of offsetof's existence.

Actually most of the above are probably copy and paste of code predating the kernel having a global offsetof definition.

Mathematics is the supreme nostalgia of our time.
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