Merge branch 'vfs-cleanups' (random vfs cleanups)

This teaches vfs_fstat() to use the appropriate f[get|put]_light
functions, allowing it to avoid some unnecessary locking for the common
case.

More noticeably, it also cleans up and simplifies the "getname_flags()"
function, which now relies on the architecture strncpy_from_user() doing
all the user access checks properly, instead of hacking around the fact
that on x86 it didn't use to do it right (see commit 92ae03f2ef99: "x86:
merge 32/64-bit versions of 'strncpy_from_user()' and speed it up").

* vfs-cleanups:
VFS: make vfs_fstat() use f[get|put]_light()
VFS: clean up and simplify getname_flags()
x86: make word-at-a-time strncpy_from_user clear bytes at the end

arch/x86/lib/usercopy.c

···
 }
 EXPORT_SYMBOL_GPL(copy_from_user_nmi);
 
-static inline unsigned long count_bytes(unsigned long mask)
-{
-	mask = (mask - 1) & ~mask;
-	mask >>= 7;
-	return count_masked_bytes(mask);
-}
-
 /*
  * Do a strncpy, return length of string without final '\0'.
  * 'count' is the user-supplied count (return 'count' if we
···
 		max = count;
 
 	while (max >= sizeof(unsigned long)) {
-		unsigned long c;
+		unsigned long c, mask;
 
 		/* Fall back to byte-at-a-time if we get a page fault */
 		if (unlikely(__get_user(c,(unsigned long __user *)(src+res))))
 			break;
-		/* This can write a few bytes past the NUL character, but that's ok */
+		mask = has_zero(c);
+		if (mask) {
+			mask = (mask - 1) & ~mask;
+			mask >>= 7;
+			*(unsigned long *)(dst+res) = c & mask;
+			return res + count_masked_bytes(mask);
+		}
 		*(unsigned long *)(dst+res) = c;
-		c = has_zero(c);
-		if (c)
-			return res + count_bytes(c);
 		res += sizeof(unsigned long);
 		max -= sizeof(unsigned long);
 	}

fs/namei.c

···
  * POSIX.1 2.4: an empty pathname is invalid (ENOENT).
  * PATH_MAX includes the nul terminator --RR.
  */
-static int do_getname(const char __user *filename, char *page)
-{
-	int retval;
-	unsigned long len = PATH_MAX;
-
-	if (!segment_eq(get_fs(), KERNEL_DS)) {
-		if ((unsigned long) filename >= TASK_SIZE)
-			return -EFAULT;
-		if (TASK_SIZE - (unsigned long) filename < PATH_MAX)
-			len = TASK_SIZE - (unsigned long) filename;
-	}
-
-	retval = strncpy_from_user(page, filename, len);
-	if (retval > 0) {
-		if (retval < len)
-			return 0;
-		return -ENAMETOOLONG;
-	} else if (!retval)
-		retval = -ENOENT;
-	return retval;
-}
-
 static char *getname_flags(const char __user *filename, int flags, int *empty)
 {
-	char *result = __getname();
-	int retval;
+	char *result = __getname(), *err;
+	int len;
 
-	if (!result)
+	if (unlikely(!result))
 		return ERR_PTR(-ENOMEM);
 
-	retval = do_getname(filename, result);
-	if (retval < 0) {
-		if (retval == -ENOENT && empty)
+	len = strncpy_from_user(result, filename, PATH_MAX);
+	err = ERR_PTR(len);
+	if (unlikely(len < 0))
+		goto error;
+
+	/* The empty path is special. */
+	if (unlikely(!len)) {
+		if (empty)
 			*empty = 1;
-		if (retval != -ENOENT || !(flags & LOOKUP_EMPTY)) {
-			__putname(result);
-			return ERR_PTR(retval);
-		}
+		err = ERR_PTR(-ENOENT);
+		if (!(flags & LOOKUP_EMPTY))
+			goto error;
 	}
-	audit_getname(result);
-	return result;
+
+	err = ERR_PTR(-ENAMETOOLONG);
+	if (likely(len < PATH_MAX)) {
+		audit_getname(result);
+		return result;
+	}
+
+error:
+	__putname(result);
+	return err;
 }
 
 char *getname(const char __user * filename)

fs/stat.c

···
 
 int vfs_fstat(unsigned int fd, struct kstat *stat)
 {
-	struct file *f = fget(fd);
+	int fput_needed;
+	struct file *f = fget_light(fd, &fput_needed);
 	int error = -EBADF;
 
 	if (f) {
 		error = vfs_getattr(f->f_path.mnt, f->f_path.dentry, stat);
-		fput(f);
+		fput_light(f, fput_needed);
 	}
 	return error;
 }