[PATCH v2 2/3] qga: add implementation of guest-get-disks for Linux

[Tomáš Golembiovský]

The command lists all disks (real and virtual) as well as disk
partitions. For each disk the list of slave disks is also listed and
/dev path is used as a handle so it can be matched with "name" filed of
other returned disk entries. For disk partitions the "slave" list is
populated with the the parent device for easier tracking of hierarchy.

Example output:
{
  "return": [
    ...
    {
      "name": "/dev/dm-0",
      "partition": false,
      "slaves": [
        "/dev/sda2"
      ],
      "alias": "luks-7062202e-5b9b-433e-81e8-6628c40da9f7"
    },
    {
      "name": "/dev/sda2",
      "partition": true,
      "slaves": [
        "/dev/sda"
      ]
    },
    {
      "name": "/dev/sda",
      "partition": false,
      "address": {
        "serial": "SAMSUNG_MZ7LN512HCHP-000L1_S1ZKNXAG822493",
        "bus-type": "sata",
        ...
        "dev": "/dev/sda",
        "target": 0
      },
      "slaves": []
    },
    ...
  ]
}

Signed-off-by: Tomáš Golembiovský <tgolembi@redhat.com>
---
 qga/commands-posix.c | 247 +++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 240 insertions(+), 7 deletions(-)

diff --git a/qga/commands-posix.c b/qga/commands-posix.c
index f99731af51..3babc25c09 100644
--- a/qga/commands-posix.c
+++ b/qga/commands-posix.c
@@ -62,6 +62,9 @@ extern char **environ;
 #endif
 #endif
 
+G_DEFINE_AUTOPTR_CLEANUP_FUNC(GuestFilesystemInfo,
+    qapi_free_GuestFilesystemInfo)
+
 static void ga_wait_child(pid_t pid, int *status, Error **errp)
 {
     pid_t rpid;
@@ -1150,6 +1153,21 @@ static void build_guest_fsinfo_for_virtual_device(char 
const *syspath,
     closedir(dir);
 }
 
+static bool is_disk_virtual(const char *devpath, Error **errp)
+{
+    g_autofree char *syspath = realpath(devpath, NULL);
+
+    if (!syspath) {
+        error_setg_errno(errp, errno, "realpath(\"%s\")", devpath);
+        return false;
+    }
+    if (strstr(syspath, "/devices/virtual/block/")) {
+        return true;
+    } else {
+        return false;
+    }
+}
+
 /* Dispatch to functions for virtual/real device */
 static void build_guest_fsinfo_for_device(char const *devpath,
                                           GuestFilesystemInfo *fs,
@@ -1168,6 +1186,7 @@ static void build_guest_fsinfo_for_device(char const 
*devpath,
 
     g_debug("  parse sysfs path '%s'", syspath);
 
+    /* TODO: use is_disk_virtual() */
     if (strstr(syspath, "/devices/virtual/block/")) {
         build_guest_fsinfo_for_virtual_device(syspath, fs, errp);
     } else {
@@ -1177,6 +1196,225 @@ static void build_guest_fsinfo_for_device(char const 
*devpath,
     free(syspath);
 }
 
+#ifdef CONFIG_LIBUDEV
+
+/*
+ * Wrapper around build_guest_fsinfo_for_device() for getting just
+ * the disk address.
+ */
+static GuestDiskAddress *get_disk_address(const char *syspath, Error **errp)
+{
+    g_autoptr(GuestFilesystemInfo) fs = NULL;
+
+    fs = g_new0(GuestFilesystemInfo, 1);
+    build_guest_fsinfo_for_device(syspath, fs, errp);
+    if (fs->disk != NULL) {
+        return g_steal_pointer(&fs->disk->value);
+    }
+    return NULL;
+}
+
+static char *get_alias_for_syspath(const char *syspath)
+{
+    struct udev *udev = NULL;
+    struct udev_device *udevice = NULL;
+    char *ret = NULL;
+
+    udev = udev_new();
+    udevice = udev_device_new_from_syspath(udev, syspath);
+    if (udev == NULL || udevice == NULL) {
+        g_debug("failed to query udev");
+    } else {
+        const char *alias = udev_device_get_property_value(
+            udevice, "DM_NAME");
+        if (alias != NULL && *alias != 0) {
+            ret = g_strdup(alias);
+        }
+    }
+
+    udev_unref(udev);
+    udev_device_unref(udevice);
+    return ret;
+}
+
+static char *get_device_for_syspath(const char *syspath)
+{
+    struct udev *udev = NULL;
+    struct udev_device *udevice = NULL;
+    char *ret = NULL;
+
+    udev = udev_new();
+    udevice = udev_device_new_from_syspath(udev, syspath);
+    if (udev == NULL || udevice == NULL) {
+        g_debug("failed to query udev");
+    } else {
+        ret = g_strdup(udev_device_get_devnode(udevice));
+    }
+    udev_unref(udev);
+    udev_device_unref(udevice);
+    return ret;
+}
+
+GuestDiskInfoList *qmp_guest_get_disks(Error **errp)
+{
+    GuestDiskInfoList *item, *ret = NULL;
+    GuestDiskInfo *disk, *partition;
+    DIR *dp = NULL;
+    struct dirent *de = NULL;
+
+    g_debug("listing /sys/block directory");
+    dp = opendir("/sys/block");
+    if (dp == NULL) {
+        error_setg_errno(errp, errno, "Can't open directory \"/sys/block\"");
+        return NULL;
+    }
+    while ((de = readdir(dp)) != NULL) {
+        g_autofree char *disk_dir = NULL, *line = NULL,
+            *size_dir = NULL, *slaves_dir = NULL;
+        struct dirent *de_disk, *de_slaves;
+        DIR *dp_disk = NULL, *dp_slaves = NULL;
+        FILE *fp = NULL;
+        size_t n = 0;
+        Error *local_err = NULL;
+        if (de->d_type != DT_LNK) {
+            g_debug("  skipping entry: %s", de->d_name);
+            continue;
+        }
+
+        /* Check size and skip zero-sized disks */
+        g_debug("  checking disk size");
+        size_dir = g_strdup_printf("/sys/block/%s/size", de->d_name);
+        fp = fopen(size_dir, "r");
+        if (!fp) {
+            g_debug("  failed to read disk size");
+            continue;
+        }
+        if (getline(&line, &n, fp) == -1) {
+            g_debug("  failed to read disk size");
+            fclose(fp);
+            continue;
+        }
+        fclose(fp);
+        if (strcmp(line, "0\n") == 0) {
+            g_debug("  skipping zero-sized disk");
+            continue;
+        }
+
+        g_debug("  adding %s", de->d_name);
+        disk_dir = g_strdup_printf("/sys/block/%s", de->d_name);
+        disk = g_new0(GuestDiskInfo, 1);
+        disk->name = get_device_for_syspath(disk_dir);
+        disk->partition = false;
+        disk->alias = get_alias_for_syspath(disk_dir);
+        if (disk->alias != NULL) {
+            disk->has_alias = true;
+        }
+        item = g_new0(GuestDiskInfoList, 1);
+        item->value = disk;
+        item->next = ret;
+        ret = item;
+
+        /* Get address for non-virtual devices */
+        bool is_virtual = is_disk_virtual(disk_dir, &local_err);
+        if (local_err != NULL) {
+            g_debug("  failed to check disk path, ignoring error: %s",
+                error_get_pretty(local_err));
+            error_free(local_err);
+            local_err = NULL;
+            /* Don't try to get the address */
+            is_virtual = true;
+        }
+        if (!is_virtual) {
+            disk->address = get_disk_address(disk_dir, &local_err);
+            if (local_err != NULL) {
+                g_debug("  failed to get device info, ignoring error: %s",
+                    error_get_pretty(local_err));
+                error_free(local_err);
+                local_err = NULL;
+            } else if (disk->address != NULL) {
+                disk->has_address = true;
+            }
+        }
+
+        /* List slave disks */
+        slaves_dir = g_strdup_printf("%s/slaves", disk_dir);
+        g_debug("  listing entries in: %s", slaves_dir);
+        dp_slaves = opendir(slaves_dir);
+        while ((de_slaves = readdir(dp_slaves)) != NULL) {
+            g_autofree char *slave_dir = NULL;
+            char *slave_dev;
+            strList *slave_item = NULL;
+
+            if ((strcmp(".", de_slaves->d_name) == 0) ||
+                (strcmp("..", de_slaves->d_name) == 0)) {
+                continue;
+            }
+
+            /* Add slave disks */
+            slave_dir = g_strdup_printf("%s/%s",
+                slaves_dir, de_slaves->d_name);
+            slave_dev = get_device_for_syspath(slave_dir);
+            if (slave_dev != NULL) {
+                g_debug("  adding slave device: %s", slave_dev);
+                slave_item = g_new0(strList, 1);
+                slave_item->value = slave_dev;
+                slave_item->next = disk->slaves;
+                disk->slaves = slave_item;
+            }
+        }
+        closedir(dp_slaves);
+
+        /*
+         * Detect partitions subdirectory name is "<parent><number>" or
+         * "<parent>p<number>"
+         */
+        dp_disk = opendir(disk_dir);
+        while ((de_disk = readdir(dp_disk)) != NULL) {
+            size_t len;
+            g_autofree char *partition_dir = NULL;
+
+            if (!(de_disk->d_type & DT_DIR)) {
+                continue;
+            }
+
+            len = strlen(de->d_name);
+            if (!(strncmp(de->d_name, de_disk->d_name, len) == 0 &&
+                ((*(de_disk->d_name + len) == 'p' &&
+                isdigit(*(de_disk->d_name + len + 1))) ||
+                    isdigit(*(de_disk->d_name + len))))) {
+                continue;
+            }
+
+            partition_dir = g_strdup_printf("%s/%s",
+                disk_dir, de_disk->d_name);
+            partition = g_new0(GuestDiskInfo, 1);
+            partition->name = get_device_for_syspath(partition_dir);
+            partition->partition = true;
+            /* Add parent disk as slave for easier tracking of hierarchy */
+            partition->slaves = g_new0(strList, 1);
+            partition->slaves->value = g_strdup(disk->name);
+
+            item = g_new0(GuestDiskInfoList, 1);
+            item->value = partition;
+            item->next = ret;
+            ret = item;
+
+        }
+        closedir(dp_disk);
+    }
+    return ret;
+}
+
+#else
+
+GuestDiskInfoList *qmp_guest_get_disks(Error **errp)
+{
+    error_setg(errp, QERR_UNSUPPORTED);
+    return NULL;
+}
+
+#endif
+
 /* Return a list of the disk device(s)' info which @mount lies on */
 static GuestFilesystemInfo *build_guest_fsinfo(struct FsMount *mount,
                                                Error **errp)
@@ -2809,7 +3047,8 @@ GList *ga_command_blacklist_init(GList *blacklist)
         const char *list[] = {
             "guest-get-fsinfo", "guest-fsfreeze-status",
             "guest-fsfreeze-freeze", "guest-fsfreeze-freeze-list",
-            "guest-fsfreeze-thaw", "guest-get-fsinfo", NULL};
+            "guest-fsfreeze-thaw", "guest-get-fsinfo",
+            "guest-get-disks", NULL};
         char **p = (char **)list;
 
         while (*p) {
@@ -3042,9 +3281,3 @@ GuestOSInfo *qmp_guest_get_osinfo(Error **errp)
 
     return info;
 }
-
-GuestDiskInfoList *qmp_guest_get_disks(Error **errp)
-{
-    error_setg(errp, QERR_UNSUPPORTED);
-    return NULL;
-}
-- 
2.25.0