_sandboxchroot.py: Improve mount interface

buildstream/_sandboxchroot.py

@@ -34,16 +34,78 @@ from . import utils, _signals
 from . import Sandbox, SandboxFlags
 
 
+class Mount():
+    def __init__(self, platform):
+        self.platform = platform
+
+    def _mount(self, src, dest, mount_type=None, options=None):
+
+        argv = [utils.get_host_tool('mount')]
+        if mount_type:
+            argv.extend([self.platform.switch(sunos='-F', default='-t'), mount_type])
+        if options:
+            argv.extend(['-o', options])
+
+        process = subprocess.Popen(
+            argv + [src, dest],
+            stdout=subprocess.PIPE,
+            stderr=subprocess.PIPE
+        )
+
+        _, err = process.communicate()
+        status = process.poll()
+
+        if status != 0:
+            raise ElementError('Mounting {} failed with exit code {}:\n{}'
+                               .format(src, status, err.decode('utf-8')))
+
+        return dest
+
+    def _umount(self, path):
+
+        args = self.platform.switch(linux='-l', default=[])
+
+        process = subprocess.Popen(
+            [utils.get_host_tool('umount'), args, path],
+            stdout=subprocess.PIPE,
+            stderr=subprocess.PIPE
+        )
+
+        _, err = process.communicate()
+        status = process.poll()
+
+        if status != 0:
+            raise ElementError('Unmounting {} failed with exit code {}:\n{}'
+                               .format(path, status, err.decode('utf-8')))
+
+    @contextmanager
+    def mount(self, src, dest, mount_type=None, **kwargs):
+
+        options = ','.join([key for key, val in kwargs.items() if val])
+
+        yield self._mount(src, dest, mount_type, options)
+
+        self._umount(dest)
+
+    @contextmanager
+    def bind_mount(self, src, dest, **kwargs):
+
+        options = ','.join([key for key, val in kwargs.items() if val])
+
+        options += self.platform.switch(linux=',' if options else '' + 'rbind',
+                                        aix=',' if options else '' + 'rbind',
+                                        sunos='')
+
+        mount_type = self.platform.switch(aix='lofs', default=None)
+
+        yield self._mount(src, dest, mount_type, options)
+
+        self._umount(dest)
+
 class SandboxChroot(Sandbox):
     def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
-
-        self._mount_bind = self._get_context()._platform.switch(
-            sunos=[utils.get_host_tool('mount'), '-F', 'lofs'],
-            aix=[utils.get_host_tool('mount'), '-o', 'bind'],
-            linux=[utils.get_host_tool('mount'), '--rbind'],
-            # openbsd=[utils.get_host_tool('mount_nullfs')]
-        )
+        self.mount = Mount(self._get_context()._platform)
 
     def run(self, command, flags, cwd=None, env=None):
 
@@ -115,7 +177,7 @@ class SandboxChroot(Sandbox):
 
         with ExitStack() as stack:
             stack.enter_context(self.create_devices(flags))
-            stack.enter_context(self.mount(flags))
+            stack.enter_context(self.mount_dirs(flags))
 
             stack.enter_context(_signals.suspendable(suspend, resume))
             stack.enter_context(_signals.terminator(terminate))
@@ -256,7 +318,7 @@ class SandboxChroot(Sandbox):
 
         with ExitStack() as stack:
             stack.enter_context(self.create_devices(flags))
-            stack.enter_context(self.mount(flags))
+            stack.enter_context(self.mount_dirs(flags))
 
             process = subprocess.Popen(
                 [utils.get_host_tool('chroot'), self.get_directory()] + command,
@@ -306,147 +368,28 @@ class SandboxChroot(Sandbox):
     #    flags (:class:`.SandboxFlags`): The sandbox flags
     #
     @contextmanager
-    def mount(self, flags):
-        mounting = []
-
-        if flags & SandboxFlags.INTERACTIVE:
-            mount_point = self.create_mount_point('/dev/', 'dir')
-            mounting.append(self.mount_bind('/dev/', mount_point))
-
-        mount_point = self.create_mount_point('/proc/', 'dir')
-        mounting.append(self.mount_proc(mount_point))
-
-        mount_point = self.create_mount_point('/tmp/', 'dir')
-        mounting.append(self.mount_bind('/tmp/', mount_point))
-
-        # User defined
-        # mount_map = MountMap(self, False)
-        # root_mount_source = mount_map.get_mount_source('/')
-        # mount_root_cmd = self._mount_bind + [root_mount_source, '/']
-
-        for point, process in mounting:
-            _, err = process.communicate()
-            status = process.poll()
-
-            if not status == 0:
-                raise ElementError('Mounting {} failed with exit code {}: {}'
-                                   .format(point, status, err.decode('utf-8')))
-
-        yield
-
-        unmounting = []
-        for point, _ in mounting:
-            unmounting.append(self.unmount(point))
-
-        for point, process in unmounting:
-            _, err = process.communicate()
-            status = process.poll()
-
-            if status != 0:
-                raise ElementError('Unmounting {} failed with exit code {}:\n{}'
-                                   .format(point, status, err.decode('utf-8')))
-
-            point = os.path.join(self.get_directory(), point.lstrip(os.sep))
+    def mount_dirs(self, flags):
 
-            # Try removing a file first, in case we mounted a file.
-            try:
-                os.remove(point)
-
-            # If the file is a directory, remove the directory.
-            except IsADirectoryError:
-                shutil.rmtree(point)
-
-            # If no file is found, the file was removed by umount.
-            except FileNotFoundError:
-                pass
-
-    # mount_bind()
-    #
-    # Create a binding mount from the given source to a target in the sandbox.
-    #
-    # Args:
-    #    source (str): The directory or file to mount
-    #    target (str): The directory or file inside the sandbox to mount to
-    #    stdout (file): The stdout to report to
-    #    stderr (file): The stderr to report to
-    #
-    # Returns:
-    #    (tuple): (sandbox_target, process)
-    #
-    def mount_bind(self, source, point):
-        process = subprocess.Popen(
-            self._mount_bind + [source, point],
-            stdout=subprocess.PIPE,
-            stderr=subprocess.PIPE
-        )
-
-        return (point, process)
-
-    # mount_proc()
-    #
-    # Mount the proc device - do *not* use mount_bind() for this.
-    #
-    def mount_proc(self, point):
-
-        cmd = self._get_context()._platform.switch(
-            sunos=[utils.get_host_tool('mount'), '-F', 'proc', '/proc', point],
-            linux=[utils.get_host_tool('mount'), '-t', 'proc', '/proc', point],
-            aix=[utils.get_host_tool('mount'), '-o', 'bind', '/proc', point],
-            # openbsd=[utils.get_host_tool('mount_nullfs')]
-        )
-
-        process = subprocess.Popen(
-            cmd,
-            stdout=subprocess.PIPE,
-            stderr=subprocess.PIPE
-        )
-
-        return (point, process)
-
-    # unmount()
-    #
-    # Unmount a directory in the sandbox.
-    #
-    # Args:
-    #    target (str): The directory or file inside the sandbox to unmount
-    #    stdout (file): The stdout to report to
-    #    stderr (file): The stderr to report to
-    #
-    # Returns:
-    #    (tuple): (sandbox_target, process)
-    #
-    def unmount(self, point):
-        process = subprocess.Popen(
-            [utils.get_host_tool('umount'), point],
-            stdout=subprocess.PIPE,
-            stderr=subprocess.PIPE
-        )
+        with ExitStack() as stack:
+            if flags & SandboxFlags.INTERACTIVE:
+                point = os.path.join(self.get_directory(), '/dev/'.lstrip(os.sep))
+                os.makedirs(point, exist_ok=True)
+                stack.enter_context(self.mount.bind_mount('/dev/', point))
 
-        return (point, process)
+            point = os.path.join(self.get_directory(), '/proc/'.lstrip(os.sep))
+            os.makedirs(point, exist_ok=True)
+            stack.enter_context(self.mount.mount('/proc/', point, 'proc', ro=True))
 
-    # create_mount_point()
-    #
-    # Create a mount point.
-    #
-    # Args:
-    #     target (str): The path to create
-    #     kind ('file'|'dir'): Whether to create a file or a dir
-    #
-    # Returns:
-    #    (str): The location of the mount point
-    #
-    def create_mount_point(self, target, kind):
-        mount_point = os.path.join(self.get_directory(), target.lstrip(os.sep))
+            point = os.path.join(self.get_directory(), '/tmp/'.lstrip(os.sep))
+            os.makedirs(point, exist_ok=True)
+            stack.enter_context(self.mount.bind_mount('/tmp/', point))
 
-        if kind == 'dir':
-            os.makedirs(mount_point, exist_ok=True)
-        elif kind == 'file':
-            try:
-                open(mount_point, mode='x')
-            except FileExistsError:
-                pass
+            # User defined
+            # mount_map = MountMap(self, False)
+            # root_mount_source = mount_map.get_mount_source('/')
+            # mount_root_cmd = self._mount_bind + [root_mount_source, '/']
 
-        return mount_point
+            yield
 
     # mknod()
     #