add a feature to balance write to load lowest rw disk

examples/fstab

@@ -0,0 +1 @@
+/data/backup1=RW:/data/backup2=RW /data/backup unionfs  rw,cow,max_files=32768,allow_other,use_ino,suid,dev,nonempty,lbwrite 0 0

mount.unionfs

@@ -1,9 +1,9 @@
 #!/bin/bash
-
-label=$1
+export PATH=/sbin:/usr/local/bin:/bin:/usr/bin
+src=$1
 mpoint=$2
 shift 3
 dirs=${@##*,dirs=}
 dirs=${dirs/,/:}
-mount.fuse "unionfs#$dirs" "$mpoint" -o ${@%%,dirs=*} 
+mount.fuse "unionfs#$src" "$mpoint" -o ${@%%,dirs=*} 
 

src/findbranch.c

@@ -41,6 +41,7 @@
 #include <stdio.h>
 #include <stdbool.h>
 #include <errno.h>
+#include <sys/vfs.h> 
 
 #include "unionfs.h"
 #include "opts.h"
@@ -137,9 +138,10 @@ int __find_rw_branch_cutlast(const char *path, int rw_hint) {
 
 	// Reminder rw_hint == -1 -> autodetect, we do not care which branch it is
 	if (uopt.branches[branch].rw 
+        && uopt.lbwrite == false
 	&& (rw_hint == -1 || branch == rw_hint)) goto out;
 
-	if (!uopt.cow_enabled) {
+	if (!uopt.cow_enabled && !uopt.lbwrite) {
 		// So path exists, but is not writable.
 		branch = -1;
 		errno = EACCES;
@@ -149,7 +151,12 @@ int __find_rw_branch_cutlast(const char *path, int rw_hint) {
 	int branch_rw;
 	// since it is a directory, any rw-branch is fine
 	if (rw_hint == -1)
-		branch_rw = find_lowest_rw_branch(uopt.nbranches);
+	        if (uopt.lbwrite == true){
+			branch_rw = find_loadlowest_rw_branch(uopt.nbranches);
+		}
+		else{
+			branch_rw = find_lowest_rw_branch(uopt.nbranches);
+		}
 	else
 		branch_rw = rw_hint;
 
@@ -236,3 +243,31 @@ int find_lowest_rw_branch(int branch_ro) {
 
 	RETURN(-1);
 }
+
+/**
+ * Find load lowest possible writable branch but only lower than branch_ro.
+ */
+int find_loadlowest_rw_branch(int branch_ro) {
+	DBG_IN();
+        struct statfs stb;
+        int res, retVal = -1;
+	unsigned long long free_space,max_free_space = 0; 
+
+	int i = 0;
+	for (i = 0; i < branch_ro; i++) {
+                res = statfs(uopt.branches[i].path, &stb);
+                if (res == -1) {
+                        retVal = -errno;
+                        break;
+                } 
+		free_space=stb.f_bsize*stb.f_bfree;
+	        DBG("branch %s free space %llu\n",uopt.branches[i].path,free_space);
+		if ( free_space > max_free_space ){
+			retVal = i;
+			max_free_space = free_space;
+		}
+	}
+
+	if (retVal >= 0) RETURN(retVal); // found it it.
+	RETURN(-1);
+}

src/findbranch.h

@@ -14,6 +14,7 @@ typedef enum searchflag {
 
 int find_rorw_branch(const char *path);
 int find_lowest_rw_branch(int branch_ro);
+int find_loadlowest_rw_branch(int branch_ro);
 int find_rw_branch_cutlast(const char *path);
 int __find_rw_branch_cutlast(const char *path, int rw_hint);
 int find_rw_branch_cow(const char *path);

src/opts.c

@@ -296,6 +296,7 @@ static void print_help(const char *progname) {
 	"    -o relaxed_permissions Disable permissions checks, but only if\n"
 	"                           running neither as UID=0 or GID=0\n"
 	"    -o statfs_omit_ro      do not count blocks of ro-branches\n"
+	"    -o lbwrite             write to each disks load balancely\n"
 	"\n",
 	progname);
 }
@@ -395,6 +396,9 @@ int unionfs_opt_proc(void *data, const char *arg, int key, struct fuse_args *out
 		case KEY_RELAXED_PERMISSIONS:
 			uopt.relaxed_permissions = true;
 			return 0;
+		case KEY_LBWRITE:
+			uopt.lbwrite = true;
+			return 0;
 		case KEY_VERSION:
 			printf("unionfs-fuse version: "VERSION"\n");
 #ifdef HAVE_XATTR

src/opts.h

@@ -30,10 +30,12 @@ typedef struct {
 	pthread_rwlock_t dbgpath_lock; // locks dbgpath
 	bool hide_meta_files;
 	bool relaxed_permissions;
+	bool lbwrite;
 
 } uopt_t;
 
 enum {
+        KEY_LBWRITE,
 	KEY_CHROOT,
 	KEY_COW,
 	KEY_DEBUG_FILE,

src/unionfs.c

@@ -68,6 +68,7 @@
 #endif
 
 static struct fuse_opt unionfs_opts[] = {
+	FUSE_OPT_KEY("lbwrite", KEY_LBWRITE),
 	FUSE_OPT_KEY("chroot=%s,", KEY_CHROOT),
 	FUSE_OPT_KEY("cow", KEY_COW),
 	FUSE_OPT_KEY("debug_file=%s", KEY_DEBUG_FILE),

test

@@ -0,0 +1,98 @@
+#!/bin/bash
+# this is a legacy version (will be removed in the future). please use test.py.
+
+set -v
+set -e
+
+rm -rf original union working-copy
+mkdir original union working-copy original/play-dir original/del-dir
+echo v1 > original/file
+echo v1 > original/play-with-me
+echo v1 > original/delete-me
+
+cleanup() {
+    if [ -e "union" ]; then fusermount -u -q union; fi
+    rm -rf union original working-copy
+}
+trap cleanup EXIT
+
+src/unionfs -d -o cow working-copy=rw:original=ro union >unionfs.log 2>&1 &
+
+sleep 1
+
+[ "$(cat union/file)" = "v1" ]
+
+echo "v2" > union/file
+[ "$(cat union/file)" = "v2" ]
+
+echo "v2" > union/play-with-me
+[ "$(cat union/play-with-me)" = "v2" ]
+
+[ -f union/play-with-me ]
+rm union/play-with-me
+[ ! -f union/play-with-me ]
+
+[ -f union/delete-me ]
+rm union/delete-me
+[ ! -f union/delete-me ]
+
+[ "$(ls union/play-dir)" = "" ]
+echo "fool" > union/play-dir/foo
+[ "$(ls union/play-dir)" = "foo" ]
+rm union/play-dir/foo
+[ "$(ls union/play-dir)" = "" ]
+
+[ -d union/play-dir ]
+rmdir union/play-dir
+[ ! -d union/play-dir ]
+
+[ -d union/del-dir ]
+rmdir union/del-dir
+[ ! -d union/del-dir ]
+
+! echo v1 > union/del-dir/foo
+
+[ ! -d union/del-dir ]
+mkdir union/del-dir
+[ ! -f union/del-dir/foo ]
+echo v1 > union/del-dir/foo
+[ -f union/del-dir/foo ]
+rm union/del-dir/foo
+[ -d union/del-dir ]
+rmdir union/del-dir
+[ ! -d union/del-dir ]
+
+# rmdir() test
+set +e
+set +v
+rc=0
+mkdir original/testdir
+touch original/testdir/testfile
+mkdir working-copy/testdir
+rmdir union/testdir 2>/dev/null
+if [ $? -eq 0 ]; then
+	echo "rmdir succeeded, although it must not"
+	rc=$(($rc + $?))
+fi
+rm union/testdir/testfile
+rc=$(($rc + $?))
+rmdir union/testdir/
+rc=$(($rc + $?))
+if [ $rc -ne 0 ]; then
+	echo "rmdir test failed"
+	exit 1
+else
+	echo "rmdir test passed"
+fi
+set -e
+
+fusermount -u union
+
+[ "$(cat original/file)" = "v1" ]
+[ "$(cat original/play-with-me)" = "v1" ]
+[ "$(cat original/delete-me)" = "v1" ]
+[ -d original/play-dir ]
+[ -d original/del-dir ]
+[ "$(cat working-copy/file)" = "v2" ]
+
+echo "ALL TEST PASSED"

test.py

@@ -25,7 +25,6 @@ def read_from_file(fn):
 def get_dir_contents(directory):
 	return [dirs for (_, dirs, _) in os.walk(directory)]
 
-
 class Common:
 	def setUp(self):
 		self.unionfs_path = os.path.abspath('src/unionfs')
@@ -69,6 +68,57 @@ def tearDown(self):
 
 		shutil.rmtree(self.tmpdir)
 
+class CommonWithImg:
+	def setUp(self):
+		self.unionfs_path = os.path.abspath('src/unionfs')
+		self.unionfsctl_path = os.path.abspath('src/unionfsctl')
+
+		self.tmpdir = tempfile.mkdtemp()
+		#self.tmpdir = "/tmp/123"
+		self.original_cwd = os.getcwd()
+		os.chdir(self.tmpdir)
+
+		self._dirs = ['ro1', 'ro2', 'rw1', 'rw2']
+
+		for d in self._dirs:
+			#call("dd if=/dev/zero of=%s/%s.img bs=4M count=25" % self.tmpdir,d)
+			call('dd if=/dev/zero of=%s/%s.img bs=4M count=5 2>/dev/null' % (str(self.tmpdir),d))
+			call('mkfs.ext4 %s/%s.img 2>/dev/null' % (self.tmpdir,d))
+			os.mkdir(d)
+			call('mount -o loop %s/%s.img %s/%s' % (self.tmpdir,d, self.tmpdir,d))
+			call('rm -rf %s/%s/*' % (self.tmpdir,d))
+			write_to_file('%s/%s_file' % (d, d), d)
+			write_to_file('%s/common_file' % d, d)
+
+		write_to_file('ro1/ro_common_file', 'ro1')
+		write_to_file('ro2/ro_common_file', 'ro2')
+		write_to_file('rw1/rw_common_file', 'rw1')
+		write_to_file('rw2/rw_common_file', 'rw2')
+
+		os.mkdir('union')
+
+	def tearDown(self):
+		# In User Mode Linux, fusermount -u union fails with a permission error
+		# when trying to lock the fuse lock file.
+
+		if os.environ.get('RUNNING_ON_TRAVIS_CI'):
+			# TODO: investigate the following
+			# the sleep seems to be needed for some users or else the umount fails
+			# anyway, everything works fine on my system, so why wait? ;-)
+			# if it fails for someone, let's find the race and fix it!
+			# actually had to re-enable it because travis-ci is one of the bad cases
+			time.sleep(1)
+
+			call('umount union')
+		else:
+			call('fusermount -u union')
+
+		os.chdir(self.original_cwd)
+		for d in self._dirs:
+			call("umount %s/%s" % (self.tmpdir,d))
+
+		shutil.rmtree(self.tmpdir)
+
 
 class UnionFS_RO_RO_TestCase(Common, unittest.TestCase):
 	def setUp(self):
@@ -274,6 +324,44 @@ def test_posix_operations(self):
 			op(union)
 			self.assertNotEqual(get_dir_contents(union), get_dir_contents(cow_path))
 
+class UnionFS_LBWRITE_TestCase(CommonWithImg, unittest.TestCase):
+	def setUp(self):
+		super().setUp()
+		call('%s -o lbwrite rw1=rw:rw2=rw union' % self.unionfs_path)
+
+	def test_listing(self):
+		lst = ['rw1_file', 'rw2_file', 'rw_common_file', 'common_file']
+		self.assertEqual(set(lst), set(os.listdir('union')))
+
+	def test_delete(self):
+		os.remove('union/rw1_file')
+
+		self.assertNotIn('rw1_file', os.listdir('union'))
+		self.assertNotIn('rw1_file', os.listdir('rw1'))
+
+	def test_write(self):
+		write_to_file('union/rw1_file', 'something')
+
+		self.assertEqual(read_from_file('union/rw1_file'), 'something')
+		self.assertEqual(read_from_file('rw1/rw1_file'), 'something')
+
+	def test_write_new(self):
+		write_to_file('union/new_file1', 'something1')
+		write_to_file('union/new_file2', 'something2')
+		self.assertEqual(read_from_file('union/new_file1'), 'something1')
+		self.assertEqual(read_from_file('union/new_file2'), 'something2')
+		self.assertEqual(read_from_file('rw1/new_file1'), 'something1')
+		self.assertEqual(read_from_file('rw2/new_file2'), 'something2')
+		self.assertNotIn('new_file1', os.listdir('rw2'))
+		self.assertNotIn('new_file2', os.listdir('rw1'))
+
+	def test_rename(self):
+		os.rename('union/rw1_file', 'union/rw1_file_renamed')
+		self.assertEqual(read_from_file('union/rw1_file_renamed'), 'rw1')
+
+	def test_copystat(self):
+		shutil.copystat('union/rw1_file', 'union/rw2_file')
+
 
 class UnionFS_RO_RW_TestCase(Common, unittest.TestCase):
 	def setUp(self):