vfs: move dentry_cmp from <linux/dcache.h> to fs/dcache.c

It's only used inside fs/dcache.c, and we're going to play games with it
for the word-at-a-time patches.  This time we really don't even want to
export it, because it really is an internal function to fs/dcache.c, and
has been since it was introduced.

Having it in that extremely hot header file (it's included in pretty
much everything, thanks to <linux/fs.h>) is a disaster for testing
different versions, and is utterly pointless.

We really should have some kind of header file diet thing, where we
figure out which parts of header files are really better off private and
only result in more expensive compiles.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/dcache.c

@@ -137,6 +137,26 @@ int proc_nr_dentry(ctl_table *table, int write, void __user *buffer,
 }
 #endif
 
+/*
+ * Compare 2 name strings, return 0 if they match, otherwise non-zero.
+ * The strings are both count bytes long, and count is non-zero.
+ */
+static inline int dentry_cmp(const unsigned char *cs, size_t scount,
+				const unsigned char *ct, size_t tcount)
+{
+	if (scount != tcount)
+		return 1;
+
+	do {
+		if (*cs != *ct)
+			return 1;
+		cs++;
+		ct++;
+		tcount--;
+	} while (tcount);
+	return 0;
+}
+
 static void __d_free(struct rcu_head *head)
 {
 	struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu);

include/linux/dcache.h

@@ -47,26 +47,6 @@ struct dentry_stat_t {
 };
 extern struct dentry_stat_t dentry_stat;
 
-/*
- * Compare 2 name strings, return 0 if they match, otherwise non-zero.
- * The strings are both count bytes long, and count is non-zero.
- */
-static inline int dentry_cmp(const unsigned char *cs, size_t scount,
-				const unsigned char *ct, size_t tcount)
-{
-	if (scount != tcount)
-		return 1;
-
-	do {
-		if (*cs != *ct)
-			return 1;
-		cs++;
-		ct++;
-		tcount--;
-	} while (tcount);
-	return 0;
-}
-
 /* Name hashing routines. Initial hash value */
 /* Hash courtesy of the R5 hash in reiserfs modulo sign bits */
 #define init_name_hash()		0