vfs: fix warning: 'dirent' is used uninitialized in this function

Using:

	gcc (GCC) 4.5.0 20100610 (prerelease)

The following warnings appear:

	fs/readdir.c: In function `filldir64':
	fs/readdir.c:240:15: warning: `dirent' is used uninitialized in this function
	fs/readdir.c: In function `filldir':
	fs/readdir.c:155:15: warning: `dirent' is used uninitialized in this function
	fs/compat.c: In function `compat_filldir64':
	fs/compat.c:1071:11: warning: `dirent' is used uninitialized in this function
	fs/compat.c: In function `compat_filldir':
	fs/compat.c:984:15: warning: `dirent' is used uninitialized in this function

The warnings are related to the use of the NAME_OFFSET() macro.  Luckily,
it appears as though the standard offsetof() macro is what is being
implemented by NAME_OFFSET(), thus we can fix the warning and use a more
standard code construct at the same time.

Signed-off-by: Kevin Winchester <kjwinchester@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/compat.c

@@ -15,6 +15,7 @@
  *  published by the Free Software Foundation.
  */
 
+#include <linux/stddef.h>
 #include <linux/kernel.h>
 #include <linux/linkage.h>
 #include <linux/compat.h>
@@ -891,8 +892,6 @@ asmlinkage long compat_sys_mount(char __user * dev_name, char __user * dir_name,
 	return retval;
 }
 
-#define NAME_OFFSET(de) ((int) ((de)->d_name - (char __user *) (de)))
-
 struct compat_old_linux_dirent {
 	compat_ulong_t	d_ino;
 	compat_ulong_t	d_offset;
@@ -981,7 +980,8 @@ static int compat_filldir(void *__buf, const char *name, int namlen,
 	struct compat_linux_dirent __user * dirent;
 	struct compat_getdents_callback *buf = __buf;
 	compat_ulong_t d_ino;
-	int reclen = ALIGN(NAME_OFFSET(dirent) + namlen + 2, sizeof(compat_long_t));
+	int reclen = ALIGN(offsetof(struct compat_linux_dirent, d_name) +
+		namlen + 2, sizeof(compat_long_t));
 
 	buf->error = -EINVAL;	/* only used if we fail.. */
 	if (reclen > buf->count)
@@ -1068,8 +1068,8 @@ static int compat_filldir64(void * __buf, const char * name, int namlen, loff_t
 {
 	struct linux_dirent64 __user *dirent;
 	struct compat_getdents_callback64 *buf = __buf;
-	int jj = NAME_OFFSET(dirent);
-	int reclen = ALIGN(jj + namlen + 1, sizeof(u64));
+	int reclen = ALIGN(offsetof(struct linux_dirent64, d_name) + namlen + 1,
+		sizeof(u64));
 	u64 off;
 
 	buf->error = -EINVAL;	/* only used if we fail.. */

fs/readdir.c

@@ -4,6 +4,7 @@
  *  Copyright (C) 1995  Linus Torvalds
  */
 
+#include <linux/stddef.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/time.h>
@@ -54,7 +55,6 @@ EXPORT_SYMBOL(vfs_readdir);
  * anyway. Thus the special "fillonedir()" function for that
  * case (the low-level handlers don't need to care about this).
  */
-#define NAME_OFFSET(de) ((int) ((de)->d_name - (char __user *) (de)))
 
 #ifdef __ARCH_WANT_OLD_READDIR
 
@@ -152,7 +152,8 @@ static int filldir(void * __buf, const char * name, int namlen, loff_t offset,
 	struct linux_dirent __user * dirent;
 	struct getdents_callback * buf = (struct getdents_callback *) __buf;
 	unsigned long d_ino;
-	int reclen = ALIGN(NAME_OFFSET(dirent) + namlen + 2, sizeof(long));
+	int reclen = ALIGN(offsetof(struct linux_dirent, d_name) + namlen + 2,
+		sizeof(long));
 
 	buf->error = -EINVAL;	/* only used if we fail.. */
 	if (reclen > buf->count)
@@ -237,7 +238,8 @@ static int filldir64(void * __buf, const char * name, int namlen, loff_t offset,
 {
 	struct linux_dirent64 __user *dirent;
 	struct getdents_callback64 * buf = (struct getdents_callback64 *) __buf;
-	int reclen = ALIGN(NAME_OFFSET(dirent) + namlen + 1, sizeof(u64));
+	int reclen = ALIGN(offsetof(struct linux_dirent64, d_name) + namlen + 1,
+		sizeof(u64));
 
 	buf->error = -EINVAL;	/* only used if we fail.. */
 	if (reclen > buf->count)