btrfs: add and fix comments in btrfs_fs_devices

	 */

	struct btrfs_device *latest_dev;

	/* all of the devices in the FS, protected by a mutex

	 * so we can safely walk it to write out the supers without

	 * worrying about add/remove by the multi-device code.

	 * Scrubbing super can kick off supers writing by holding

	 * this mutex lock.

	/*

	 * All of the devices in the filesystem, protected by a mutex so we can

	 * safely walk it to write out the super blocks without worrying about

	 * adding/removing by the multi-device code. Scrubbing super block can

	 * kick off supers writing by holding this mutex lock.

	 */

	struct mutex device_list_mutex;

	/* List of all devices, protected by device_list_mutex */

	struct list_head devices;

	/*

	 * Devices which can satisfy space allocation. Protected by

	 * chunk_mutex

	 */

	/* Devices which can satisfy space allocation. Protected by * chunk_mutex. */

	struct list_head alloc_list;

	struct list_head seed_list;

	/* Count fs-devices opened. */

	int opened;

	/* set when we find or add a device that doesn't have the

	 * nonrot flag set

	 */

	/* Set when we find or add a device that doesn't have the nonrot flag set. */

	bool rotating;

	/* Devices support TRIM/discard commands */

	/* Devices support TRIM/discard commands. */

	bool discardable;

	bool fsid_change;

	/* The filesystem is a seed filesystem. */

	bool seeding;

	struct btrfs_fs_info *fs_info;

	enum btrfs_chunk_allocation_policy chunk_alloc_policy;

	/* Policy used to read the mirrored stripes */

	/* Policy used to read the mirrored stripes. */

	enum btrfs_read_policy read_policy;

};