[PATCH 1/3] discover: Keep track of available ramdisk devices

[Cyril Bur]

On Wed, 2015-05-13 at 17:14 +1000, Samuel Mendoza-Jonas wrote:
> Store information on available ramdisk devices when they are recognised
> by udev, and add functions to 'reserve' and 'release' these devices.
> 
> This will be used to associate device-mapper snapshots with a backing
> ramdisk in a following patch.

Reviewed-by: Cyril Bur <cyril.bur at au1.ibm.com>

> 
> Signed-off-by: Samuel Mendoza-Jonas <sam.mj at au1.ibm.com>
> ---
>  discover/device-handler.c | 92 +++++++++++++++++++++++++++++++++++++++++++++++
>  discover/device-handler.h | 14 ++++++++
>  2 files changed, 106 insertions(+)
> 
> diff --git a/discover/device-handler.c b/discover/device-handler.c
> index fb7baba..efdd5f9 100644
> --- a/discover/device-handler.c
> +++ b/discover/device-handler.c
> @@ -56,6 +56,9 @@ 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;
> @@ -752,6 +755,95 @@ void device_handler_add_device(struct device_handler *handler,
>  		network_register_device(handler->network, device);
>  }
>  
> +void device_handler_add_ramdisk(struct device_handler *handler,
> +		const char *path)
> +{
> +	struct ramdisk_device *dev;
> +	unsigned int i;
> +
> +	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 {
> +			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_release_ramdisk(struct discover_device *device)
> +{
> +	struct ramdisk_device *ramdisk = device->ramdisk;
> +
> +	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
>   * array, but has only just been initialised by the hotplug source.
>   */
> diff --git a/discover/device-handler.h b/discover/device-handler.h
> index b592c46..5877733 100644
> --- a/discover/device-handler.h
> +++ b/discover/device-handler.h
> @@ -26,6 +26,7 @@ struct discover_device {
>  
>  	char			*mount_path;
>  	const char		*device_path;
> +	struct ramdisk_device	*ramdisk;
>  	bool			mounted;
>  	bool			mounted_rw;
>  	bool			unmount;
> @@ -59,6 +60,14 @@ struct discover_context {
>  	void			*test_data;
>  };
>  
> +struct ramdisk_device {
> +	const char	*path;
> +	char		*snapshot;
> +	char		*origin;
> +	char		*base;
> +	unsigned int	sectors;
> +};
> +
>  struct device_handler *device_handler_init(struct discover_server *server,
>  		struct waitset *waitset, int dry_run);
>  
> @@ -72,6 +81,11 @@ struct discover_device *discover_device_create(struct device_handler *handler,
>  		const char *id);
>  void device_handler_add_device(struct device_handler *handler,
>  		struct discover_device *device);
> +void device_handler_add_ramdisk(struct device_handler *handler,
> +		const char *path);
> +struct ramdisk_device *device_handler_get_ramdisk(
> +		struct device_handler *handler);
> +void device_handler_release_ramdisk(struct discover_device *device);
>  int device_handler_discover(struct device_handler *handler,
>  		struct discover_device *dev);
>  int device_handler_dhcp(struct device_handler *handler,