device: add infrastructure to support external device info

lib/Makefile.in

@@ -56,6 +56,7 @@ SOURCES =\
 	datastruct/btree.c \
 	datastruct/str_list.c \
 	device/dev-cache.c \
+	device/dev-ext.c \
 	device/dev-io.c \
 	device/dev-md.c \
 	device/dev-swap.c \

lib/device/dev-cache.c

@@ -64,6 +64,9 @@ static void _dev_init(struct device *dev, int max_error_count)
 	dev->read_ahead = -1;
 	dev->max_error_count = max_error_count;
 
+	dev->ext.enabled = 0;
+	dev->ext.src = DEV_EXT_NONE;
+
 	dm_list_init(&dev->aliases);
 	dm_list_init(&dev->open_list);
 }

lib/device/dev-ext.c

@@ -0,0 +1,164 @@
+/*
+ * Copyright (C) 2014 Red Hat, Inc. All rights reserved.
+ *
+ * This file is part of LVM2.
+ *
+ * This copyrighted material is made available to anyone wishing to use,
+ * modify, copy, or redistribute it subject to the terms and conditions
+ * of the GNU Lesser General Public License v.2.1.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#include "lib.h"
+#include "device.h"
+
+#ifdef UDEV_SYNC_SUPPORT
+#include <libudev.h>
+#endif
+
+struct ext_registry_item {
+	const char *name;
+	struct dev_ext *(* dev_ext_get) (struct device *dev);
+	int (*dev_ext_release) (struct device *dev);
+};
+
+#define EXT_REGISTER(id,name) [id] = { #name, &_dev_ext_get_ ## name, &_dev_ext_release_ ## name }
+
+/*
+ * DEV_EXT_NONE
+ */
+static struct dev_ext *_dev_ext_get_none(struct device *dev)
+{
+	dev->ext.handle = NULL;
+	return &dev->ext;
+}
+
+static int _dev_ext_release_none(struct device *dev)
+{
+	dev->ext.handle = NULL;
+	return 1;
+}
+
+/*
+ * DEV_EXT_UDEV
+ */
+static struct dev_ext *_dev_ext_get_udev(struct device *dev)
+{
+#ifdef UDEV_SYNC_SUPPORT
+	struct udev *udev;
+	struct udev_device *udev_device;
+
+	if (dev->ext.handle)
+		return &dev->ext;
+
+	if (!(udev = udev_get_library_context()))
+		return_NULL;
+
+	if (!(udev_device = udev_device_new_from_devnum(udev, 'b', dev->dev)))
+		return_NULL;
+
+	dev->ext.handle = (void *) udev_device;
+	return &dev->ext;
+#else
+	return NULL;
+#endif
+}
+
+static int _dev_ext_release_udev(struct device *dev)
+{
+#ifdef UDEV_SYNC_SUPPORT
+	if (!dev->ext.handle)
+		return 1;
+
+	/* udev_device_unref can't fail - it has no return value */
+	udev_device_unref((struct udev_device *) dev->ext.handle);
+	dev->ext.handle = NULL;
+	return 1;
+#else
+	return 0;
+#endif
+}
+
+static struct ext_registry_item _ext_registry[DEV_EXT_NUM] = {
+	EXT_REGISTER(DEV_EXT_NONE, none),
+	EXT_REGISTER(DEV_EXT_UDEV, udev)
+};
+
+const char *dev_ext_name(struct device *dev)
+{
+	return _ext_registry[dev->ext.src].name;
+}
+
+static const char *_ext_attached_msg = "External handle attached to device";
+
+struct dev_ext *dev_ext_get(struct device *dev)
+{
+	struct dev_ext *ext;
+	void *handle_ptr;
+
+	handle_ptr = dev->ext.handle;
+
+	if (!(ext = _ext_registry[dev->ext.src].dev_ext_get(dev)))
+		log_error("Failed to get external handle for device %s [%s].",
+			   dev_name(dev), dev_ext_name(dev));
+	else if (handle_ptr != dev->ext.handle)
+		log_debug_devs("%s %s [%s:%p]", _ext_attached_msg, dev_name(dev),
+				dev_ext_name(dev), dev->ext.handle);
+
+	return ext;
+}
+
+int dev_ext_release(struct device *dev)
+{
+	int r;
+	void *handle_ptr;
+
+	if (!dev->ext.enabled ||
+	    !dev->ext.handle)
+		return 1;
+
+	handle_ptr = dev->ext.handle;
+
+	if (!(r = _ext_registry[dev->ext.src].dev_ext_release(dev)))
+		log_error("Failed to release external handle for device %s [%s:%p].",
+			  dev_name(dev), dev_ext_name(dev), dev->ext.handle);
+	else
+		log_debug_devs("External handle detached from device %s [%s:%p]",
+				dev_name(dev), dev_ext_name(dev), handle_ptr);
+
+	return r;
+}
+
+int dev_ext_enable(struct device *dev, dev_ext_t src)
+{
+	if (dev->ext.enabled && (dev->ext.src != src) && !dev_ext_release(dev)) {
+		log_error("Failed to enable external handle for device %s [%s].",
+			   dev_name(dev), _ext_registry[src].name); 
+		return 0;
+	}
+
+	dev->ext.src = src;
+	dev->ext.enabled = 1;
+
+	return 1;
+}
+
+int dev_ext_disable(struct device *dev)
+{
+	if (!dev->ext.enabled)
+		return 1;
+
+	if (!dev_ext_release(dev)) {
+		log_error("Failed to disable external handle for device %s [%s].",
+			   dev_name(dev), dev_ext_name(dev));
+		return 0;
+	}
+
+	dev->ext.enabled = 0;
+	dev->ext.src = DEV_EXT_NONE;
+
+	return 1;
+}

lib/device/device.h

@@ -28,6 +28,23 @@
 #define DEV_O_DIRECT		0x00000020	/* Use O_DIRECT */
 #define DEV_O_DIRECT_TESTED	0x00000040	/* DEV_O_DIRECT is reliable */
 
+/*
+ * Support for external device info.
+ * Any new external device info source needs to be
+ * registered using EXT_REGISTER macro in dev-ext.c.
+ */
+typedef enum {
+	DEV_EXT_NONE,
+	DEV_EXT_UDEV,
+	DEV_EXT_NUM
+} dev_ext_t;
+
+struct dev_ext {
+	int enabled;
+	dev_ext_t src;
+	void *handle;
+};
+
 /*
  * All devices in LVM will be represented by one of these.
  * pointer comparisons are valid.
@@ -47,6 +64,7 @@ struct device {
 	uint32_t flags;
 	uint64_t end;
 	struct dm_list open_list;
+	struct dev_ext ext;
 
 	char pvid[ID_LEN + 1];
 	char _padding[7];
@@ -63,6 +81,15 @@ struct device_area {
 	uint64_t size;		/* Bytes */
 };
 
+/*
+ * Support for external device info.
+ */
+const char *dev_ext_name(struct device *dev);
+int dev_ext_enable(struct device *dev, dev_ext_t src);
+int dev_ext_disable(struct device *dev);
+struct dev_ext *dev_ext_get(struct device *dev);
+int dev_ext_release(struct device *dev);
+
 /*
  * All io should use these routines.
  */