]> git.ozlabs.org Git - petitboot/blobdiff - discover/device-handler.c
discover: Add 'sync' user event
[petitboot] / discover / device-handler.c
index f0537134c1a3bc2a517f40b8cc385525940dfe0b..c31fceaf5a11b1ac22c28f50ad530866f4b7f23e 100644 (file)
@@ -26,6 +26,7 @@
 
 #include "device-handler.h"
 #include "discover-server.h"
+#include "devmapper.h"
 #include "user-event.h"
 #include "platform.h"
 #include "event.h"
@@ -40,8 +41,7 @@
 
 enum default_priority {
        DEFAULT_PRIORITY_REMOTE         = 1,
-       DEFAULT_PRIORITY_LOCAL_UUID     = 2,
-       DEFAULT_PRIORITY_LOCAL_FIRST    = 3,
+       DEFAULT_PRIORITY_LOCAL_FIRST    = 2,
        DEFAULT_PRIORITY_LOCAL_LAST     = 0xfe,
        DEFAULT_PRIORITY_DISABLED       = 0xff,
 };
@@ -57,6 +57,9 @@ struct device_handler {
        struct discover_device  **devices;
        unsigned int            n_devices;
 
+       struct ramdisk_device   **ramdisks;
+       unsigned int            n_ramdisks;
+
        struct waitset          *waitset;
        struct waiter           *timeout_waiter;
        bool                    autoboot_enabled;
@@ -320,6 +323,7 @@ struct device_handler *device_handler_init(struct discover_server *server,
 void device_handler_reinit(struct device_handler *handler)
 {
        struct discover_boot_option *opt, *tmp;
+       struct ramdisk_device *ramdisk;
        unsigned int i;
 
        device_handler_cancel_default(handler);
@@ -331,13 +335,20 @@ void device_handler_reinit(struct device_handler *handler)
        list_init(&handler->unresolved_boot_options);
 
        /* drop all devices */
-       for (i = 0; i < handler->n_devices; i++)
+       for (i = 0; i < handler->n_devices; i++) {
                discover_server_notify_device_remove(handler->server,
                                handler->devices[i]->device);
+               ramdisk = handler->devices[i]->ramdisk;
+               talloc_free(handler->devices[i]);
+               talloc_free(ramdisk);
+       }
 
        talloc_free(handler->devices);
        handler->devices = NULL;
        handler->n_devices = 0;
+       talloc_free(handler->ramdisks);
+       handler->ramdisks = NULL;
+       handler->n_ramdisks = 0;
 
        device_handler_reinit_sources(handler);
 }
@@ -348,6 +359,15 @@ void device_handler_remove(struct device_handler *handler,
        struct discover_boot_option *opt, *tmp;
        unsigned int i;
 
+       list_for_each_entry_safe(&device->boot_options, opt, tmp, list) {
+               if (opt == handler->default_boot_option) {
+                       pb_log("Default option %s cancelled since device removed",
+                                       opt->option->name);
+                       device_handler_cancel_default(handler);
+                       break;
+               }
+       }
+
        for (i = 0; i < handler->n_devices; i++)
                if (handler->devices[i] == device)
                        break;
@@ -385,7 +405,7 @@ void device_handler_remove(struct device_handler *handler,
        talloc_free(device);
 }
 
-static void boot_status(void *arg, struct boot_status *status)
+void device_handler_boot_status(void *arg, struct boot_status *status)
 {
        struct device_handler *handler = arg;
 
@@ -434,8 +454,11 @@ static int default_timeout(void *arg)
 
        pb_log("Timeout expired, booting default option %s\n", opt->option->id);
 
+       platform_pre_boot();
+
        handler->pending_boot = boot(handler, handler->default_boot_option,
-                       NULL, handler->dry_run, boot_status, handler);
+                       NULL, handler->dry_run, device_handler_boot_status,
+                       handler);
        handler->pending_boot_is_default = true;
        return 0;
 }
@@ -446,6 +469,7 @@ struct {
 } device_type_map[] = {
        { IPMI_BOOTDEV_NETWORK, DEVICE_TYPE_NETWORK },
        { IPMI_BOOTDEV_DISK, DEVICE_TYPE_DISK },
+       { IPMI_BOOTDEV_DISK, DEVICE_TYPE_USB },
        { IPMI_BOOTDEV_CDROM, DEVICE_TYPE_OPTICAL },
 };
 
@@ -462,11 +486,27 @@ static bool ipmi_device_type_matches(enum ipmi_bootdev ipmi_type,
        return false;
 }
 
-static bool priority_matches(struct boot_priority *prio,
-               struct discover_boot_option *opt)
+static int autoboot_option_priority(const struct config *config,
+                               struct discover_boot_option *opt)
 {
-       return prio->type == opt->device->device->type ||
-               prio->type == DEVICE_TYPE_ANY;
+       enum device_type type = opt->device->device->type;
+       const char *uuid = opt->device->uuid;
+       struct autoboot_option *auto_opt;
+       unsigned int i;
+
+       for (i = 0; i < config->n_autoboot_opts; i++) {
+               auto_opt = &config->autoboot_opts[i];
+               if (auto_opt->boot_type == BOOT_DEVICE_UUID)
+                       if (!strcmp(auto_opt->uuid, uuid))
+                               return DEFAULT_PRIORITY_LOCAL_FIRST + i;
+
+               if (auto_opt->boot_type == BOOT_DEVICE_TYPE)
+                       if (auto_opt->type == type ||
+                           auto_opt->type == DEVICE_TYPE_ANY)
+                               return DEFAULT_PRIORITY_LOCAL_FIRST + i;
+       }
+
+       return -1;
 }
 
 /*
@@ -478,8 +518,6 @@ static enum default_priority default_option_priority(
                struct discover_boot_option *opt)
 {
        const struct config *config;
-       const char *dev_str;
-       unsigned int i;
 
        config = config_get();
 
@@ -498,25 +536,17 @@ static enum default_priority default_option_priority(
                return DEFAULT_PRIORITY_DISABLED;
        }
 
-       /* Next, allow matching by device UUID. If we have one set but it
-        * doesn't match, disallow the default entirely */
-       dev_str = config->boot_device;
-       if (dev_str && dev_str[0]) {
-               if (!strcmp(opt->device->uuid, dev_str))
-                       return DEFAULT_PRIORITY_LOCAL_UUID;
-
-               pb_debug("handler: disabled default priority due to "
-                               "non-matching UUID\n");
-               return DEFAULT_PRIORITY_DISABLED;
-       }
-
-       /* Lastly, use the local priorities */
-       for (i = 0; i < config->n_boot_priorities; i++) {
-               struct boot_priority *prio = &config->boot_priorities[i];
-               if (priority_matches(prio, opt))
-                       return DEFAULT_PRIORITY_LOCAL_FIRST + prio->priority;
+       /* Next, try to match the option against the user-defined autoboot
+        * options, either by device UUID or type. */
+       if (config->n_autoboot_opts) {
+               int boot_match = autoboot_option_priority(config, opt);
+               if (boot_match > 0)
+                       return boot_match;
        }
 
+       /* If the option didn't match any entry in the array, it is disabled */
+       pb_debug("handler: disabled default priority due to "
+                       "non-matching UUID or type\n");
        return DEFAULT_PRIORITY_DISABLED;
 }
 
@@ -687,60 +717,105 @@ struct discover_context *device_handler_discover_context_create(
        return ctx;
 }
 
-/**
- * context_commit - Commit a temporary discovery context to the handler,
- * and notify the clients about any new options / devices
- */
-void device_handler_discover_context_commit(struct device_handler *handler,
-               struct discover_context *ctx)
+void device_handler_add_device(struct device_handler *handler,
+               struct discover_device *device)
 {
-       struct discover_device *dev = ctx->device;
-       struct discover_boot_option *opt, *tmp;
+       handler->n_devices++;
+       handler->devices = talloc_realloc(handler, handler->devices,
+                               struct discover_device *, handler->n_devices);
+       handler->devices[handler->n_devices - 1] = device;
 
-       if (!device_lookup_by_id(handler, dev->device->id))
-               device_handler_add_device(handler, dev);
+       if (device->device->type == DEVICE_TYPE_NETWORK)
+               network_register_device(handler->network, device);
+}
 
-       /* move boot options from the context to the device */
-       list_for_each_entry_safe(&ctx->boot_options, opt, tmp, list) {
-               list_remove(&opt->list);
+void device_handler_add_ramdisk(struct device_handler *handler,
+               const char *path)
+{
+       struct ramdisk_device *dev;
+       unsigned int i;
 
-               if (boot_option_resolve(opt, handler)) {
-                       pb_log("boot option %s is resolved, "
-                                       "sending to clients\n",
-                                       opt->option->id);
-                       list_add_tail(&dev->boot_options, &opt->list);
-                       talloc_steal(dev, opt);
-                       boot_option_finalise(handler, opt);
-                       notify_boot_option(handler, opt);
+       if (!path)
+               return;
+
+       for (i = 0; i < handler->n_ramdisks; i++)
+               if (!strcmp(handler->ramdisks[i]->path, path))
+                       return;
+
+       dev = talloc_zero(handler, struct ramdisk_device);
+       if (!dev) {
+               pb_log("Failed to allocate memory to track %s\n", path);
+               return;
+       }
+
+       dev->path = talloc_strdup(handler, path);
+
+       handler->ramdisks = talloc_realloc(handler, handler->ramdisks,
+                               struct ramdisk_device *,
+                               handler->n_ramdisks + 1);
+       if (!handler->ramdisks) {
+               pb_log("Failed to reallocate memory"
+                      "- ramdisk tracking inconsistent!\n");
+               return;
+       }
+
+       handler->ramdisks[i] = dev;
+       i = handler->n_ramdisks++;
+}
+
+struct ramdisk_device *device_handler_get_ramdisk(
+               struct device_handler *handler)
+{
+       unsigned int i;
+       char *name;
+       dev_t id;
+
+       /* Check if free ramdisk exists */
+       for (i = 0; i < handler->n_ramdisks; i++)
+               if (!handler->ramdisks[i]->snapshot &&
+                   !handler->ramdisks[i]->origin &&
+                   !handler->ramdisks[i]->base)
+                       return handler->ramdisks[i];
+
+       /* Otherwise create a new one */
+       name = talloc_asprintf(handler, "/dev/ram%d",
+                       handler->n_ramdisks);
+       if (!name) {
+               pb_debug("Failed to allocate memory to name /dev/ram%d",
+                       handler->n_ramdisks);
+               return NULL;
+       }
+
+       id = makedev(1, handler->n_ramdisks);
+       if (mknod(name, S_IFBLK, id)) {
+               if (errno == EEXIST) {
+                       /* We haven't yet received updates for existing
+                        * ramdisks - add and use this one */
+                       pb_debug("Using untracked ramdisk %s\n", name);
                } else {
-                       if (!opt->source->resolve_resource) {
-                               pb_log("parser %s gave us an unresolved "
-                                       "resource (%s), but no way to "
-                                       "resolve it\n",
-                                       opt->source->name, opt->option->id);
-                               talloc_free(opt);
-                       } else {
-                               pb_log("boot option %s is unresolved, "
-                                               "adding to queue\n",
-                                               opt->option->id);
-                               list_add(&handler->unresolved_boot_options,
-                                               &opt->list);
-                               talloc_steal(handler, opt);
-                       }
+                       pb_log("Failed to create new ramdisk %s: %s\n",
+                              name, strerror(errno));
+                       return NULL;
                }
        }
+       device_handler_add_ramdisk(handler, name);
+       talloc_free(name);
+
+       return handler->ramdisks[i];
 }
 
-void device_handler_add_device(struct device_handler *handler,
-               struct discover_device *device)
+void device_handler_release_ramdisk(struct discover_device *device)
 {
-       handler->n_devices++;
-       handler->devices = talloc_realloc(handler, handler->devices,
-                               struct discover_device *, handler->n_devices);
-       handler->devices[handler->n_devices - 1] = device;
+       struct ramdisk_device *ramdisk = device->ramdisk;
 
-       if (device->device->type == DEVICE_TYPE_NETWORK)
-               network_register_device(handler->network, device);
+       talloc_free(ramdisk->snapshot);
+       talloc_free(ramdisk->origin);
+       talloc_free(ramdisk->base);
+
+       ramdisk->snapshot = ramdisk->origin = ramdisk->base = NULL;
+       ramdisk->sectors = 0;
+
+       device->ramdisk = NULL;
 }
 
 /* Start discovery on a hotplugged device. The device will be in our devices
@@ -750,8 +825,22 @@ int device_handler_discover(struct device_handler *handler,
                struct discover_device *dev)
 {
        struct discover_context *ctx;
+       struct boot_status *status;
        int rc;
 
+       status = talloc_zero(handler, struct boot_status);
+       status->type = BOOT_STATUS_INFO;
+       /*
+        * TRANSLATORS: this string will be passed the type and identifier
+        * of the device. For example, the first parameter could be "Disk",
+        * (which will be translated accordingly) and the second a Linux device
+        * identifier like 'sda1' (which will not be translated)
+        */
+       status->message = talloc_asprintf(status, _("Processing %s device %s"),
+                               device_type_display_name(dev->device->type),
+                               dev->device->id);
+       device_handler_boot_status(handler, status);
+
        process_boot_option_queue(handler);
 
        /* create our context */
@@ -772,7 +861,16 @@ int device_handler_discover(struct device_handler *handler,
        device_handler_discover_context_commit(handler, ctx);
 
 out:
-       talloc_free(ctx);
+       /*
+        * TRANSLATORS: the format specifier in this string is a Linux
+        * device identifier, like 'sda1'
+        */
+       status->message = talloc_asprintf(status,_("Processing %s complete"),
+                               dev->device->id);
+       device_handler_boot_status(handler, status);
+
+       talloc_free(status);
+       talloc_unlink(handler, ctx);
 
        return 0;
 }
@@ -782,6 +880,17 @@ int device_handler_dhcp(struct device_handler *handler,
                struct discover_device *dev, struct event *event)
 {
        struct discover_context *ctx;
+       struct boot_status *status;
+
+       status = talloc_zero(handler, struct boot_status);
+       status->type = BOOT_STATUS_INFO;
+       /*
+        * TRANSLATORS: this format specifier will be the name of a network
+        * device, like 'eth0'.
+        */
+       status->message = talloc_asprintf(status, _("Processing dhcp event on %s"),
+                               dev->device->id);
+       device_handler_boot_status(handler, status);
 
        /* create our context */
        ctx = device_handler_discover_context_create(handler, dev);
@@ -791,7 +900,16 @@ int device_handler_dhcp(struct device_handler *handler,
 
        device_handler_discover_context_commit(handler, ctx);
 
-       talloc_free(ctx);
+       /*
+        * TRANSLATORS: this format specifier will be the name of a network
+        * device, like 'eth0'.
+        */
+       status->message = talloc_asprintf(status,_("Processing %s complete"),
+                               dev->device->id);
+       device_handler_boot_status(handler, status);
+
+       talloc_free(status);
+       talloc_unlink(handler, ctx);
 
        return 0;
 }
@@ -800,19 +918,30 @@ int device_handler_dhcp(struct device_handler *handler,
 int device_handler_conf(struct device_handler *handler,
                struct discover_device *dev, struct pb_url *url)
 {
-        struct discover_context *ctx;
+       struct discover_context *ctx;
+       struct boot_status *status;
 
-        /* create our context */
-        ctx = device_handler_discover_context_create(handler, dev);
-        ctx->conf_url = url;
+       status = talloc_zero(handler, struct boot_status);
+       status->type = BOOT_STATUS_INFO;
+       status->message = talloc_asprintf(status, _("Processing user config"));
+       device_handler_boot_status(handler, status);
 
-        iterate_parsers(ctx);
+       /* create our context */
+       ctx = device_handler_discover_context_create(handler, dev);
+       ctx->conf_url = url;
+
+       iterate_parsers(ctx);
 
-        device_handler_discover_context_commit(handler, ctx);
+       device_handler_discover_context_commit(handler, ctx);
 
-        talloc_free(ctx);
+       status->message = talloc_asprintf(status,
+                               _("Processing user config complete"));
+       device_handler_boot_status(handler, status);
 
-        return 0;
+       talloc_free(status);
+       talloc_unlink(handler, ctx);
+
+       return 0;
 }
 
 static struct discover_boot_option *find_boot_option_by_id(
@@ -846,7 +975,7 @@ void device_handler_boot(struct device_handler *handler,
        platform_pre_boot();
 
        handler->pending_boot = boot(handler, opt, cmd, handler->dry_run,
-                       boot_status, handler);
+                       device_handler_boot_status, handler);
        handler->pending_boot_is_default = false;
 }
 
@@ -938,10 +1067,12 @@ static char *device_from_addr(void *ctx, struct pb_url *url)
 
        rc = process_run_sync(p);
 
-       if (rc) {
+       if (rc || p->exit_status) {
                /* ip has complained for some reason; most likely
                 * there is no route to the host - bail out */
-               pb_debug("%s: No route to %s\n",__func__,url->host);
+               pb_debug("%s: `ip` returns non-zero exit status\n", __func__);
+               pb_debug("ip buf: %s\n", p->stdout_buf);
+               process_release(p);
                return NULL;
        }
 
@@ -964,9 +1095,8 @@ static char *device_from_addr(void *ctx, struct pb_url *url)
        return dev;
 }
 
-
 void device_handler_process_url(struct device_handler *handler,
-               const char *url)
+               const char *url, const char *mac, const char *ip)
 {
        struct discover_context *ctx;
        struct discover_device *dev;
@@ -992,20 +1122,38 @@ void device_handler_process_url(struct device_handler *handler,
        event->type = EVENT_TYPE_USER;
        event->action = EVENT_ACTION_CONF;
 
-       event->params = talloc_array(event, struct param, 1);
-       param = &event->params[0];
-       param->name = talloc_strdup(event, "pxeconffile");
-       param->value = talloc_strdup(event, url);
-       event->n_params = 1;
+       if (url[strlen(url) - 1] == '/') {
+               event->params = talloc_array(event, struct param, 3);
+               param = &event->params[0];
+               param->name = talloc_strdup(event, "pxepathprefix");
+               param->value = talloc_strdup(event, url);
+               param = &event->params[1];
+               param->name = talloc_strdup(event, "mac");
+               param->value = talloc_strdup(event, mac);
+               param = &event->params[2];
+               param->name = talloc_strdup(event, "ip");
+               param->value = talloc_strdup(event, ip);
+               event->n_params = 3;
+       } else {
+               event->params = talloc_array(event, struct param, 1);
+               param = &event->params[0];
+               param->name = talloc_strdup(event, "pxeconffile");
+               param->value = talloc_strdup(event, url);
+               event->n_params = 1;
+       }
 
        pb_url = pb_url_parse(event, event->params->value);
-       if (!pb_url || !pb_url->host) {
+       if (!pb_url || (pb_url->scheme != pb_url_file && !pb_url->host)) {
                status->message = talloc_asprintf(handler,
                                        _("Invalid config URL!"));
                goto msg;
        }
 
-       event->device = device_from_addr(event, pb_url);
+       if (pb_url->scheme == pb_url_file)
+               event->device = talloc_asprintf(event, "local");
+       else
+               event->device = device_from_addr(event, pb_url);
+
        if (!event->device) {
                status->message = talloc_asprintf(status,
                                        _("Unable to route to host %s"),
@@ -1014,6 +1162,8 @@ void device_handler_process_url(struct device_handler *handler,
        }
 
        dev = discover_device_create(handler, event->device);
+       if (pb_url->scheme == pb_url_file)
+               dev->device->type = DEVICE_TYPE_ANY;
        ctx = device_handler_discover_context_create(handler, dev);
        ctx->event = event;
 
@@ -1021,18 +1171,70 @@ void device_handler_process_url(struct device_handler *handler,
 
        device_handler_discover_context_commit(handler, ctx);
 
-       talloc_free(ctx);
+       talloc_unlink(handler, ctx);
 
        status->type = BOOT_STATUS_INFO;
        status->message = talloc_asprintf(status, _("Config file %s parsed"),
                                        pb_url->file);
 msg:
-       boot_status(handler, status);
+       device_handler_boot_status(handler, status);
        talloc_free(status);
 }
 
 #ifndef PETITBOOT_TEST
 
+/**
+ * context_commit - Commit a temporary discovery context to the handler,
+ * and notify the clients about any new options / devices
+ */
+void device_handler_discover_context_commit(struct device_handler *handler,
+               struct discover_context *ctx)
+{
+       struct discover_device *dev = ctx->device;
+       struct discover_boot_option *opt, *tmp;
+
+       if (!device_lookup_by_id(handler, dev->device->id))
+               device_handler_add_device(handler, dev);
+
+       /* move boot options from the context to the device */
+       list_for_each_entry_safe(&ctx->boot_options, opt, tmp, list) {
+               list_remove(&opt->list);
+
+               /* All boot options need at least a kernel image */
+               if (!opt->boot_image || !opt->boot_image->url) {
+                       pb_log("boot option %s is missing boot image, ignoring\n",
+                               opt->option->id);
+                       talloc_free(opt);
+                       continue;
+               }
+
+               if (boot_option_resolve(opt, handler)) {
+                       pb_log("boot option %s is resolved, "
+                                       "sending to clients\n",
+                                       opt->option->id);
+                       list_add_tail(&dev->boot_options, &opt->list);
+                       talloc_steal(dev, opt);
+                       boot_option_finalise(handler, opt);
+                       notify_boot_option(handler, opt);
+               } else {
+                       if (!opt->source->resolve_resource) {
+                               pb_log("parser %s gave us an unresolved "
+                                       "resource (%s), but no way to "
+                                       "resolve it\n",
+                                       opt->source->name, opt->option->id);
+                               talloc_free(opt);
+                       } else {
+                               pb_log("boot option %s is unresolved, "
+                                               "adding to queue\n",
+                                               opt->option->id);
+                               list_add(&handler->unresolved_boot_options,
+                                               &opt->list);
+                               talloc_steal(handler, opt);
+                       }
+               }
+       }
+}
+
 static void device_handler_update_lang(const char *lang)
 {
        const char *cur_lang;
@@ -1082,28 +1284,44 @@ static void device_handler_reinit_sources(struct device_handler *handler)
                        handler->dry_run);
 }
 
-static const char *fs_parameters(unsigned int rw_flags, const char *fstype)
+static inline const char *get_device_path(struct discover_device *dev)
 {
-       if ((rw_flags | MS_RDONLY) != MS_RDONLY)
-               return "";
+       return dev->ramdisk ? dev->ramdisk->snapshot : dev->device_path;
+}
+
+static char *check_subvols(struct discover_device *dev)
+{
+       const char *fstype = discover_device_get_param(dev, "ID_FS_TYPE");
+       struct stat sb;
+       char *path;
+       int rc;
 
-       /* Avoid writing back to the disk on journaled filesystems */
-       if (!strncmp(fstype, "ext4", strlen("ext4")))
-               return "norecovery";
-       if (!strncmp(fstype, "xfs", strlen("xfs")))
-               return "norecovery";
+       if (strncmp(fstype, "btrfs", strlen("btrfs")))
+               return dev->mount_path;
 
-       return "";
+       /* On btrfs a device's root may be under a subvolume path */
+       path = join_paths(dev, dev->mount_path, "@");
+       rc = stat(path, &sb);
+       if (!rc && S_ISDIR(sb.st_mode)) {
+               pb_debug("Using '%s' for btrfs root path\n", path);
+               return path;
+       }
+
+       talloc_free(path);
+       return dev->mount_path;
 }
 
 static bool check_existing_mount(struct discover_device *dev)
 {
        struct stat devstat, mntstat;
+       const char *device_path;
        struct mntent *mnt;
        FILE *fp;
        int rc;
 
-       rc = stat(dev->device_path, &devstat);
+       device_path = get_device_path(dev);
+
+       rc = stat(device_path, &devstat);
        if (rc) {
                pb_debug("%s: stat failed: %s\n", __func__, strerror(errno));
                return false;
@@ -1134,6 +1352,7 @@ static bool check_existing_mount(struct discover_device *dev)
 
                if (mntstat.st_rdev == devstat.st_rdev) {
                        dev->mount_path = talloc_strdup(dev, mnt->mnt_dir);
+                       dev->root_path = check_subvols(dev);
                        dev->mounted_rw = !!hasmntopt(mnt, "rw");
                        dev->mounted = true;
                        dev->unmount = false;
@@ -1151,9 +1370,55 @@ static bool check_existing_mount(struct discover_device *dev)
        return mnt != NULL;
 }
 
+/*
+ * Attempt to mount a filesystem safely, while handling certain filesytem-
+ * specific options
+ */
+static int try_mount(const char *device_path, const char *mount_path,
+                            const char *fstype, unsigned long flags,
+                            bool have_snapshot)
+{
+       const char *fs, *safe_opts;
+       int rc;
+
+       /* Mount ext3 as ext4 instead so 'norecovery' can be used */
+       if (strncmp(fstype, "ext3", strlen("ext3")) == 0) {
+               pb_debug("Mounting ext3 filesystem as ext4\n");
+               fs = "ext4";
+       } else
+               fs = fstype;
+
+       if (strncmp(fs, "xfs", strlen("xfs")) == 0 ||
+           strncmp(fs, "ext4", strlen("ext4")) == 0)
+               safe_opts = "norecovery";
+       else
+               safe_opts = NULL;
+
+       errno = 0;
+       /* If no snapshot is available don't attempt recovery */
+       if (!have_snapshot)
+               return mount(device_path, mount_path, fs, flags, safe_opts);
+
+       rc = mount(device_path, mount_path, fs, flags, NULL);
+
+       if (!rc)
+               return rc;
+
+       /* Mounting failed; some filesystems will fail to mount if a recovery
+        * journal exists (eg. cross-endian XFS), so try again with norecovery
+        * where that option is available.
+        * If mounting read-write just return the error as norecovery is not a
+        * valid option */
+       if ((flags & MS_RDONLY) != MS_RDONLY || !safe_opts)
+               return rc;
+
+       errno = 0;
+       return mount(device_path, mount_path, fs, flags, safe_opts);
+}
+
 static int mount_device(struct discover_device *dev)
 {
-       const char *fstype;
+       const char *fstype, *device_path;
        int rc;
 
        if (!dev->device_path)
@@ -1169,13 +1434,6 @@ static int mount_device(struct discover_device *dev)
        if (!fstype)
                return 0;
 
-       /* ext3 treats the norecovery option as an error, so mount the device
-        * as an ext4 filesystem instead */
-       if (!strncmp(fstype, "ext3", strlen("ext3"))) {
-               pb_debug("Mounting ext3 filesystem as ext4\n");
-               fstype = talloc_asprintf(dev, "ext4");
-       }
-
        dev->mount_path = join_paths(dev, mount_base(),
                                        dev->device_path);
 
@@ -1185,20 +1443,25 @@ static int mount_device(struct discover_device *dev)
                goto err_free;
        }
 
+       device_path = get_device_path(dev);
+
        pb_log("mounting device %s read-only\n", dev->device_path);
-       errno = 0;
-       rc = mount(dev->device_path, dev->mount_path, fstype,
-                       MS_RDONLY | MS_SILENT,
-                       fs_parameters(MS_RDONLY, fstype));
+       rc = try_mount(device_path, dev->mount_path, fstype,
+                      MS_RDONLY | MS_SILENT, dev->ramdisk);
+
        if (!rc) {
                dev->mounted = true;
                dev->mounted_rw = false;
                dev->unmount = true;
+               dev->root_path = check_subvols(dev);
                return 0;
        }
 
        pb_log("couldn't mount device %s: mount failed: %s\n",
-                       dev->device_path, strerror(errno));
+                       device_path, strerror(errno));
+
+       /* If mount fails clean up any snapshot */
+       devmapper_destroy_snapshot(dev);
 
        pb_rmdir_recursive(mount_base(), dev->mount_path);
 err_free:
@@ -1209,33 +1472,43 @@ err_free:
 
 static int umount_device(struct discover_device *dev)
 {
+       const char *device_path;
        int rc;
 
        if (!dev->mounted || !dev->unmount)
                return 0;
 
-       pb_log("unmounting device %s\n", dev->device_path);
+       device_path = get_device_path(dev);
+
+       pb_log("unmounting device %s\n", device_path);
        rc = umount(dev->mount_path);
        if (rc)
                return -1;
 
        dev->mounted = false;
+       devmapper_destroy_snapshot(dev);
 
        pb_rmdir_recursive(mount_base(), dev->mount_path);
 
        talloc_free(dev->mount_path);
        dev->mount_path = NULL;
+       dev->root_path = NULL;
 
        return 0;
 }
 
 int device_request_write(struct discover_device *dev, bool *release)
 {
-       const char *fstype;
+       const char *fstype, *device_path;
+       const struct config *config;
        int rc;
 
        *release = false;
 
+       config = config_get();
+       if (!config->allow_writes)
+               return -1;
+
        if (!dev->mounted)
                return -1;
 
@@ -1244,16 +1517,19 @@ int device_request_write(struct discover_device *dev, bool *release)
 
        fstype = discover_device_get_param(dev, "ID_FS_TYPE");
 
-       pb_log("remounting device %s read-write\n", dev->device_path);
+       device_path = get_device_path(dev);
+
+       pb_log("remounting device %s read-write\n", device_path);
 
        rc = umount(dev->mount_path);
        if (rc) {
-               pb_log("Failed to unmount %s\n", dev->mount_path);
+               pb_log("Failed to unmount %s: %s\n",
+                      dev->mount_path, strerror(errno));
                return -1;
        }
-       rc = mount(dev->device_path, dev->mount_path, fstype,
-                       MS_SILENT,
-                       fs_parameters(MS_REMOUNT, fstype));
+
+       rc = try_mount(device_path, dev->mount_path, fstype,
+                      MS_SILENT, dev->ramdisk);
        if (rc)
                goto mount_ro;
 
@@ -1262,33 +1538,93 @@ int device_request_write(struct discover_device *dev, bool *release)
        return 0;
 
 mount_ro:
-       pb_log("Unable to remount device %s read-write\n", dev->device_path);
-       rc = mount(dev->device_path, dev->mount_path, fstype,
-                       MS_RDONLY | MS_SILENT,
-                       fs_parameters(MS_RDONLY, fstype));
+       pb_log("Unable to remount device %s read-write: %s\n",
+              device_path, strerror(errno));
+       rc = try_mount(device_path, dev->mount_path, fstype,
+                      MS_RDONLY | MS_SILENT, dev->ramdisk);
        if (rc)
-               pb_log("Unable to recover mount for %s\n", dev->device_path);
+               pb_log("Unable to recover mount for %s: %s\n",
+                      device_path, strerror(errno));
        return -1;
 }
 
 void device_release_write(struct discover_device *dev, bool release)
 {
-       const char *fstype;
+       const char *fstype, *device_path;
 
        if (!release)
                return;
 
+       device_path = get_device_path(dev);
+
        fstype = discover_device_get_param(dev, "ID_FS_TYPE");
 
-       pb_log("remounting device %s read-only\n", dev->device_path);
-       mount(dev->device_path, dev->mount_path, "",
-                       MS_REMOUNT | MS_RDONLY | MS_SILENT,
-                       fs_parameters(MS_RDONLY, fstype));
-       dev->mounted_rw = false;
+       pb_log("remounting device %s read-only\n", device_path);
+
+       if (umount(dev->mount_path)) {
+               pb_log("Failed to unmount %s\n", dev->mount_path);
+               return;
+       }
+       dev->mounted_rw = dev->mounted = false;
+
+       if (dev->ramdisk) {
+               devmapper_merge_snapshot(dev);
+               /* device_path becomes stale after merge */
+               device_path = get_device_path(dev);
+       }
+
+       if (try_mount(device_path, dev->mount_path, fstype,
+                      MS_RDONLY | MS_SILENT, dev->ramdisk))
+               pb_log("Failed to remount %s read-only: %s\n",
+                      device_path, strerror(errno));
+       else
+               dev->mounted = true;
+}
+
+void device_sync_snapshots(struct device_handler *handler, const char *device)
+{
+       struct discover_device *dev = NULL;
+       unsigned int i;
+
+       if (device) {
+               /* Find matching device and sync */
+               dev = device_lookup_by_name(handler, device);
+               if (!dev) {
+                       pb_log("%s: device name '%s' unrecognised\n",
+                               __func__, device);
+                       return;
+               }
+               if (dev->ramdisk)
+                       device_release_write(dev, true);
+               else
+                       pb_log("%s has no snapshot to merge, skipping\n",
+                               dev->device->id);
+               return;
+       }
+
+       /* Otherwise sync all relevant devices */
+       for (i = 0; i < handler->n_devices; i++) {
+               dev = handler->devices[i];
+               if (dev->device->type != DEVICE_TYPE_DISK &&
+                       dev->device->type != DEVICE_TYPE_USB)
+                       continue;
+               if (dev->ramdisk)
+                       device_release_write(dev, true);
+               else
+                       pb_log("%s has no snapshot to merge, skipping\n",
+                               dev->device->id);
+       }
 }
 
 #else
 
+void device_handler_discover_context_commit(
+               struct device_handler *handler __attribute__((unused)),
+               struct discover_context *ctx __attribute__((unused)))
+{
+       pb_log("%s stubbed out for test cases\n", __func__);
+}
+
 static void device_handler_update_lang(const char *lang __attribute__((unused)))
 {
 }
@@ -1327,5 +1663,10 @@ void device_release_write(struct discover_device *dev __attribute__((unused)),
 {
 }
 
-#endif
+void device_sync_snapshots(
+               struct device_handler *handler __attribute__((unused)),
+               const char *device __attribute__((unused)))
+{
+}
 
+#endif