scoutfs: add file with simple name functions

Directory entries and extended attributes similarly hash and compare
strings so we'll give them some shared functions for doing so.

Signed-off-by: Zach Brown <zab@versity.com>

kmod/src/Makefile

@@ -11,7 +11,7 @@ CFLAGS_scoutfs_trace.o = -I$(src) # define_trace.h double include
 scoutfs-y += first.o
 
 scoutfs-y += block.o btree.o buddy.o counters.o crc.o dir.o filerw.o \
-	     inode.o ioctl.o msg.o scoutfs_trace.o super.o trace.o trans.o \
-	     treap.o
+	     inode.o ioctl.o msg.o name.o scoutfs_trace.o super.o trace.o \
+	     trans.o treap.o
 
 scoutfs-y += last.o

kmod/src/dir.c

@@ -23,6 +23,7 @@
 #include "super.h"
 #include "btree.h"
 #include "trans.h"
+#include "name.h"
 
 /*
  * Directory entries are stored in entries with offsets calculated from
@@ -84,11 +85,6 @@ static unsigned int dentry_type(unsigned int type)
 	return DT_UNKNOWN;
 }
 
-static int names_equal(const char *name_a, int len_a, const char *name_b,
-		       int len_b)
-{
-	return (len_a == len_b) && !memcmp(name_a, name_b, len_a);
-}
 
 /*
  * XXX This crc nonsense is a quick hack.  We'll want something a
@@ -209,8 +205,8 @@ static struct dentry *scoutfs_lookup(struct inode *dir, struct dentry *dentry,
 
 		dent = curs.val;
 		name_len = item_name_len(&curs);
-		if (names_equal(dentry->d_name.name, dentry->d_name.len,
-				dent->name, name_len)) {
+		if (scoutfs_names_equal(dentry->d_name.name, dentry->d_name.len,
+					dent->name, name_len)) {
 			ino = le64_to_cpu(dent->ino);
 			di->hash = scoutfs_key_offset(curs.key);
 			break;

kmod/src/name.c

@@ -0,0 +1,35 @@
+/*
+ * Copyright (C) 2016 Versity Software, Inc.  All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+#include <linux/kernel.h>
+#include <linux/crc32c.h>
+#include <linux/string.h>
+
+#include "name.h"
+
+/*
+ * XXX This crc nonsense is a quick hack.  We'll want something a
+ * lot stronger like siphash.
+ */
+u64 scoutfs_name_hash(const char *name, unsigned int len)
+{
+	unsigned int half = (len + 1) / 2;
+
+	return crc32c(~0, name, half) |
+	       ((u64)crc32c(~0, name + len - half, half) << 32);
+}
+
+int scoutfs_names_equal(const char *name_a, int len_a,
+			       const char *name_b, int len_b)
+{
+	return (len_a == len_b) && !memcmp(name_a, name_b, len_a);
+}

kmod/src/name.h

@@ -0,0 +1,8 @@
+#ifndef _SCOUTFS_NAME_H_
+#define _SCOUTFS_NAME_H_
+
+u64 scoutfs_name_hash(const char *data, unsigned int len);
+int scoutfs_names_equal(const char *name_a, int len_a,
+			const char *name_b, int len_b);
+
+#endif