Index: xfstests/common/rc
===================================================================
--- xfstests.orig/common/rc
+++ xfstests/common/rc
@@ -65,6 +65,12 @@ _btrfs_get_subvolid()
 	$BTRFS_UTIL_PROG sub list $mnt | grep $name | awk '{ print $2 }'
 }
 
+_btrfs_get_fsid()
+{
+	local dev=$1
+	$BTRFS_UTIL_PROG filesystem show $dev|awk '/uuid:/ {print $NF}'
+}
+
 # Prints the md5 checksum of a given file
 _md5_checksum()
 {
Index: xfstests/src/Makefile
===================================================================
--- xfstests.orig/src/Makefile
+++ xfstests/src/Makefile
@@ -18,7 +18,8 @@ LINUX_TARGETS = xfsctl bstat t_mtab getd
 	locktest unwritten_mmap bulkstat_unlink_test t_stripealign \
 	bulkstat_unlink_test_modified t_dir_offset t_futimens t_immutable \
 	stale_handle pwrite_mmap_blocked t_dir_offset2 seek_sanity_test \
-	seek_copy_test t_readdir_1 t_readdir_2 fsync-tester nsexec
+	seek_copy_test t_readdir_1 t_readdir_2 fsync-tester nsexec \
+	btrfs_ioctl_helper
 
 SUBDIRS =
 
Index: xfstests/src/btrfs_ioctl_helper.c
===================================================================
--- /dev/null
+++ xfstests/src/btrfs_ioctl_helper.c
@@ -0,0 +1,90 @@
+#include <sys/ioctl.h>
+#include <stdio.h>
+#include <sys/fcntl.h>
+#include <errno.h>
+#include <string.h>
+#include <stdint.h>
+#include <unistd.h>
+
+#ifndef BTRFS_IOCTL_MAGIC
+#define BTRFS_IOCTL_MAGIC 0x94
+#endif
+
+#ifndef BTRFS_IOC_GLOBAL_RSV
+#define BTRFS_IOC_GLOBAL_RSV _IOR(BTRFS_IOCTL_MAGIC, 20, uint64_t)
+#endif
+
+static int global_rsv_ioctl(int fd, int argc, char *argv[])
+{
+	uint64_t reserved;
+	int ret = ioctl(fd, BTRFS_IOC_GLOBAL_RSV, &reserved);
+	if (ret)
+		return -errno;
+
+	printf("%llu\n", (unsigned long long)reserved);
+	return 0;
+}
+
+#define IOCTL_TABLE_ENTRY(_ioctl_name, _handler) \
+	{ .name = #_ioctl_name, .ioctl_cmd = BTRFS_IOC_##_ioctl_name, \
+	  .handler = _handler, }
+
+struct ioctl_table_entry {
+	const char *name;
+	unsigned ioctl_cmd;
+	int (*handler)(int fd, int argc, char *argv[]);
+};
+
+static struct ioctl_table_entry ioctls[] = {
+	IOCTL_TABLE_ENTRY(GLOBAL_RSV, global_rsv_ioctl),
+};
+
+int
+main(int argc, char *argv[])
+{
+	int fd;
+	int ret;
+	struct ioctl_table_entry *entry = NULL;
+	int i;
+
+	if (argc < 3) {
+		fprintf(stderr,
+			"usage: %s <fs mount point> <ioctl name> [args..]\n",
+			argv[0]);
+		return 1;
+	}
+
+	fd = open(argv[1], O_RDONLY|O_DIRECTORY);
+	if (fd < 0) {
+		perror(argv[1]);
+		return 1;
+	}
+
+	for (i = 0; i < (sizeof(ioctls)/sizeof(ioctls[0])); i++) {
+		if (strcmp(argv[2], ioctls[i].name) == 0) {
+			entry = &ioctls[i];
+			break;
+		}
+	}
+
+	if (!entry) {
+		fprintf(stderr, "ERROR: unknown ioctl %s\n", argv[2]);
+		close(fd);
+		return 1;
+	}
+
+	ret = entry->handler(fd, argc - 3, argv + 3);
+	if (ret == -ENOTTY) {
+		printf("Not implemented.\n");
+		close(fd);
+		return 0;
+	} else if (ret) {
+		fprintf(stderr, "ERROR: %s failed: %s\n",
+			entry->name, strerror(-ret));
+		close(fd);
+		return 1;
+	}
+
+	close(fd);
+	return 0;
+}
Index: xfstests/tests/btrfs/021
===================================================================
--- /dev/null
+++ xfstests/tests/btrfs/021
@@ -0,0 +1,88 @@
+#!/bin/bash
+# FA QA Test No. 021
+#
+# Test global metadata reservation reporting
+#
+# 1) Create empty file system
+# 2) Call the BTRFS_IOC_GLOBAL_RSV ioctl and confirm it is 0 < x < 10MB
+# 3) Read the /sys/fs/btrfs/<fsid>/allocation/global_rsv_reserved file
+#    and confirm the value is 0 < x < 10 MB
+#
+#-----------------------------------------------------------------------
+# Copyright (c) 2013 SUSE, 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 as
+# published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it would 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.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write the Free Software Foundation,
+# Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+#-----------------------------------------------------------------------
+
+seq=$(basename $0)
+seqres=$RESULT_DIR/$seq
+echo "== QA output created by $seq"
+
+here=$(pwd)
+tmp=/tmp/$$
+status=1
+
+# get standard environment, filters and checks
+. ./common/rc
+. ./common/filter.btrfs
+
+_supported_fs btrfs
+_supported_os Linux
+_require_scratch
+
+_scratch_mkfs > /dev/null 2>&1
+_scratch_mount
+
+# Check to see if the reservation is 0 < x <= 10MB
+# At the time of this writing, it should always be exactly 4 MB
+# but that is an implementation detail subject to change.
+check_reserved() {
+	reserved="$2"
+	method="$3"
+	if [ "$1" != 0 ]; then
+		echo "$method: failed: $reserved"
+		exit 1
+	fi
+	if [ "$reserved" = "Not implemented." ]; then
+		echo "Skipping ioctl test. Not implemented." >> $seqres.full
+		return
+	fi
+	if [ -n "$(echo $reserved | tr -d 0-9)" ]; then
+		echo "ERROR: numerical value expected (got $reserved)"
+		exit 1
+	fi
+	if [ "$reserved" -le 0 -o \
+	       "$reserved" -gt "$(( 10 * 1024 * 1024 ))" ]; then
+		echo "$method: out of range: $reserved."
+		exit
+	fi
+}
+
+# ioctl
+reserved="$(src/btrfs_ioctl_helper $SCRATCH_MNT GLOBAL_RSV 2>&1)"
+check_reserved $? "$reserved" "ioctl"
+
+# sysfs
+# If this directory is here, the files must be here as well
+SYSFS_PREFIX="/sys/fs/btrfs/$(_btrfs_get_fsid $SCRATCH_DEV)/allocation"
+if [ -d "$SYSFS_PREFIX" ]; then
+	reserved="$(cat $SYSFS_PREFIX/global_rsv_reserved 2>&1)"
+	check_reserved $? "$reserved" "sysfs:reserved"
+	size="$(cat $SYSFS_PREFIX/global_rsv_size 2>&1)"
+	check_reserved $? "$size" "sysfs:size"
+fi
+
+echo "Silence is golden"
+status=0
+exit
Index: xfstests/tests/btrfs/021.out
===================================================================
--- /dev/null
+++ xfstests/tests/btrfs/021.out
@@ -0,0 +1,2 @@
+QA output created by 021
+Silence is golden
