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

[Daniel P . Berrangé]

On Mon, Sep 07, 2020 at 11:14:41AM +0200, Tomáš Golembiovský wrote:
> 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);

These 10 lines can be reduced to just

    g_file_get_contents(size_dir, &line, NULL, NULL)
    

> +        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);

Since you are only using d_name, you can use g_dir_open and
g_dir_read_name and g_dir_close. This always skips . and ..
for you.

> +
> +        /*
> +         * 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
> 
> 

Regards,
Daniel
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