discover/udev: Handle LVM logical volumes
authorSamuel Mendoza-Jonas <sam@mendozajonas.com>
Wed, 14 Jun 2017 05:17:21 +0000 (15:17 +1000)
committerSamuel Mendoza-Jonas <sam@mendozajonas.com>
Tue, 11 Jul 2017 04:50:00 +0000 (14:50 +1000)
If logical volumes are active and recognised by udev, no longer ignore
them. We also do some extra handling to use user-friendly device names
and mount the /dev/mapper/foo device rather than the /dev/dm-xx device.

Additionally if we see "LMV2_member" devices start a rescan in case
LVM-formatted disks came up after the LVM initscript.

Signed-off-by: Samuel Mendoza-Jonas <sam@mendozajonas.com>
discover/udev.c

index 1e043130c7d1c61246ba5ca1518f3076bb37c331..f4754b1662b89517f159dbfd0dd265a696501d31 100644 (file)
@@ -19,6 +19,7 @@
 #include <talloc/talloc.h>
 #include <waiter/waiter.h>
 #include <system/system.h>
+#include <process/process.h>
 
 #include "event.h"
 #include "udev.h"
@@ -70,9 +71,26 @@ static void udev_setup_device_params(struct udev_device *udev,
                                udev_list_entry_get_value(entry));
 }
 
+/*
+ * Search for LVM logical volumes. If any exist they should be recognised
+ * by udev as normal.
+ * Normally this is handled in an init script, but on some platforms
+ * disks are slow enough to come up that we need to check again.
+ */
+static void lvm_vg_search(struct device_handler *handler)
+{
+       if (process_run_simple(handler, pb_system_apps.vgscan, "-qq", NULL))
+               pb_log("%s: Failed to execute vgscan\n", __func__);
+
+       if (process_run_simple(handler, pb_system_apps.vgchange, "-ay", "-qq",
+                               NULL))
+               pb_log("%s: Failed to execute vgchange\n", __func__);
+}
+
 static int udev_handle_block_add(struct pb_udev *udev, struct udev_device *dev,
                const char *name)
 {
+       char *devlinks = NULL, *link, *saveptr = NULL;
        struct discover_device *ddev;
        unsigned int i = 0;
        const char *typestr;
@@ -85,7 +103,6 @@ static int udev_handle_block_add(struct pb_udev *udev, struct udev_device *dev,
        const char *ignored_types[] = {
                "linux_raid_member",
                "swap",
-               "LVM2_member",
                NULL,
        };
        bool cdrom, usb;
@@ -124,10 +141,9 @@ static int udev_handle_block_add(struct pb_udev *udev, struct udev_device *dev,
                }
        }
 
-       /* If our environment's udev can recognise them explictly skip any
-        * device mapper devices we encounter */
+       /* Ignore any device mapper devices that aren't logical volumes */
        devname = udev_device_get_property_value(dev, "DM_NAME");
-       if (devname) {
+       if (devname && ! udev_device_get_property_value(dev, "DM_LV_NAME")) {
                pb_debug("SKIP: dm-device %s\n", devname);
                return 0;
        }
@@ -146,6 +162,12 @@ static int udev_handle_block_add(struct pb_udev *udev, struct udev_device *dev,
                i++;
        }
 
+       /* Search for LVM logical volumes if we see an LVM member */
+       if (strncmp(type, "LVM2_member", strlen("LVM2_member")) == 0) {
+               lvm_vg_search(udev->handler);
+               return 0;
+       }
+
        /* We may see multipath devices; they'll have the same uuid as an
         * existing device, so only parse the first. */
        uuid = udev_device_get_property_value(dev, "ID_FS_UUID");
@@ -158,9 +180,31 @@ static int udev_handle_block_add(struct pb_udev *udev, struct udev_device *dev,
                }
        }
 
-       ddev = discover_device_create(udev->handler, uuid, name);
+       /* Use DM_NAME for logical volumes, or the device name otherwise */
+       ddev = discover_device_create(udev->handler, uuid, devname ?: name);
+
+       if (devname) {
+               /*
+                * For logical volumes udev_device_get_devnode() returns a path
+                * of the form "/dev/dm-xx". These nodes names are not
+                * persistent and are opaque to the user. Instead use the more
+                * recognisable "/dev/mapper/lv-name" node if it is available.
+                */
+               devlinks = talloc_strdup(ddev,
+                               udev_device_get_property_value(dev, "DEVLINKS"));
+               link = devlinks ? strtok_r(devlinks, " ", &saveptr) : NULL;
+               while (link) {
+                       if (strncmp(link, "/dev/mapper/",
+                                       strlen("/dev/mapper/")) == 0) {
+                               node = link;
+                               break;
+                       }
+                       link = strtok_r(NULL, " ", &saveptr);
+               }
+       }
 
        ddev->device_path = talloc_strdup(ddev, node);
+       talloc_free(devlinks);
 
        if (uuid)
                ddev->uuid = talloc_strdup(ddev, uuid);