Add configure check for user_path_dir()

I didn't notice at the time but user_path_dir() was not introduced
at the same time as set_fs_pwd() change.  I had lumped the two
together but in fact user_path_dir() was introduced in 2.6.27 and
set_fs_pwd() taking 2 args was introduced in 2.6.25.  This means
builds against 2.6.25-2.6.26 kernels were broken.

To fix this I've added a check for user_path_dir() and no longer
assume that if set_fs_pwd() takes 2 args then user_path_dir() is
also available.

config/spl-build.m4

@@ -68,6 +68,7 @@ AC_DEFUN([SPL_AC_CONFIG_KERNEL], [
 	SPL_AC_ZONE_STAT_ITEM_INACTIVE
 	SPL_AC_ZONE_STAT_ITEM_ACTIVE
 	SPL_AC_GET_ZONE_COUNTS
+	SPL_AC_USER_PATH_DIR
 	SPL_AC_SET_FS_PWD
 	SPL_AC_2ARGS_SET_FS_PWD
 	SPL_AC_2ARGS_VFS_UNLINK
@@ -1298,6 +1299,19 @@ AC_DEFUN([SPL_AC_GET_ZONE_COUNTS], [
 	])
 ])
 
+dnl #
+dnl # 2.6.27 API change,
+dnl # The user_path_dir() replaces __user_walk()
+dnl #
+AC_DEFUN([SPL_AC_USER_PATH_DIR], [
+	SPL_CHECK_SYMBOL_EXPORT(
+		[user_path_at],
+		[],
+		[AC_DEFINE(HAVE_USER_PATH_DIR, 1,
+		[user_path_dir() is available])],
+		[])
+])
+
 dnl #
 dnl # Symbol available in RHEL kernels not in stock kernels.
 dnl #

configure

@@ -14459,6 +14459,47 @@ fi
 
 
 
+	{ $as_echo "$as_me:$LINENO: checking whether symbol user_path_at is exported" >&5
+$as_echo_n "checking whether symbol user_path_at is exported... " >&6; }
+	grep -q -E '[[:space:]]user_path_at[[:space:]]' \
+		$LINUX_OBJ/Module*.symvers 2>/dev/null
+	rc=$?
+	if test $rc -ne 0; then
+		export=0
+		for file in ; do
+			grep -q -E "EXPORT_SYMBOL.*(user_path_at)" \
+				"$LINUX_OBJ/$file" 2>/dev/null
+			rc=$?
+		        if test $rc -eq 0; then
+		                export=1
+		                break;
+		        fi
+		done
+		if test $export -eq 0; then
+			{ $as_echo "$as_me:$LINENO: result: no" >&5
+$as_echo "no" >&6; }
+
+		else
+			{ $as_echo "$as_me:$LINENO: result: yes" >&5
+$as_echo "yes" >&6; }
+
+cat >>confdefs.h <<\_ACEOF
+#define HAVE_USER_PATH_DIR 1
+_ACEOF
+
+		fi
+	else
+		{ $as_echo "$as_me:$LINENO: result: yes" >&5
+$as_echo "yes" >&6; }
+
+cat >>confdefs.h <<\_ACEOF
+#define HAVE_USER_PATH_DIR 1
+_ACEOF
+
+	fi
+
+
+
 	{ $as_echo "$as_me:$LINENO: checking whether symbol set_fs_pwd is exported" >&5
 $as_echo_n "checking whether symbol set_fs_pwd is exported... " >&6; }
 	grep -q -E '[[:space:]]set_fs_pwd[[:space:]]' \
@@ -17931,6 +17972,47 @@ fi
 
 
 
+	{ $as_echo "$as_me:$LINENO: checking whether symbol user_path_at is exported" >&5
+$as_echo_n "checking whether symbol user_path_at is exported... " >&6; }
+	grep -q -E '[[:space:]]user_path_at[[:space:]]' \
+		$LINUX_OBJ/Module*.symvers 2>/dev/null
+	rc=$?
+	if test $rc -ne 0; then
+		export=0
+		for file in ; do
+			grep -q -E "EXPORT_SYMBOL.*(user_path_at)" \
+				"$LINUX_OBJ/$file" 2>/dev/null
+			rc=$?
+		        if test $rc -eq 0; then
+		                export=1
+		                break;
+		        fi
+		done
+		if test $export -eq 0; then
+			{ $as_echo "$as_me:$LINENO: result: no" >&5
+$as_echo "no" >&6; }
+
+		else
+			{ $as_echo "$as_me:$LINENO: result: yes" >&5
+$as_echo "yes" >&6; }
+
+cat >>confdefs.h <<\_ACEOF
+#define HAVE_USER_PATH_DIR 1
+_ACEOF
+
+		fi
+	else
+		{ $as_echo "$as_me:$LINENO: result: yes" >&5
+$as_echo "yes" >&6; }
+
+cat >>confdefs.h <<\_ACEOF
+#define HAVE_USER_PATH_DIR 1
+_ACEOF
+
+	fi
+
+
+
 	{ $as_echo "$as_me:$LINENO: checking whether symbol set_fs_pwd is exported" >&5
 $as_echo_n "checking whether symbol set_fs_pwd is exported... " >&6; }
 	grep -q -E '[[:space:]]set_fs_pwd[[:space:]]' \

module/spl/spl-vnode.c

@@ -648,7 +648,7 @@ set_fs_pwd(struct fs_struct *fs, struct vfsmount *mnt, struct dentry *dentry)
 int
 vn_set_pwd(const char *filename)
 {
-#ifdef HAVE_2ARGS_SET_FS_PWD
+#if defined(HAVE_2ARGS_SET_FS_PWD) && defined(HAVE_USER_PATH_DIR)
         struct path path;
 #else
         struct nameidata nd;
@@ -666,6 +666,7 @@ vn_set_pwd(const char *filename)
         set_fs(get_ds());
 
 #ifdef HAVE_2ARGS_SET_FS_PWD
+# ifdef HAVE_USER_PATH_DIR
         rc = user_path_dir(filename, &path);
         if (rc)
                 GOTO(out, rc);
@@ -678,6 +679,21 @@ vn_set_pwd(const char *filename)
 
 dput_and_out:
         path_put(&path);
+# else
+        rc = __user_walk(filename,
+                         LOOKUP_FOLLOW|LOOKUP_DIRECTORY|LOOKUP_CHDIR, &nd);
+        if (rc)
+                GOTO(out, rc);
+
+        rc = vfs_permission(&nd, MAY_EXEC);
+        if (rc)
+                GOTO(dput_and_out, rc);
+
+        set_fs_pwd(current->fs, &nd.path);
+
+dput_and_out:
+        path_put(&nd.path);
+# endif /* HAVE_USER_PATH_DIR */
 #else
         rc = __user_walk(filename,
                          LOOKUP_FOLLOW|LOOKUP_DIRECTORY|LOOKUP_CHDIR, &nd);

spl_config.h.in

@@ -183,6 +183,9 @@
 /* Define to 1 if you have the <unistd.h> header file. */
 #undef HAVE_UNISTD_H
 
+/* user_path_dir() is available */
+#undef HAVE_USER_PATH_DIR
+
 /* Page state NR_ACTIVE is available */
 #undef HAVE_ZONE_STAT_ITEM_NR_ACTIVE