bio: add documentation to bio_alloc()

	return NULL;

}

/**

 * bio_alloc - allocate a bio for I/O

 * @gfp_mask:   the GFP_ mask given to the slab allocator

 * @nr_iovecs:	number of iovecs to pre-allocate

 *

 * Description:

 *   bio_alloc will allocate a bio and associated bio_vec array that can hold

 *   at least @nr_iovecs entries. Allocations will be done from the

 *   fs_bio_set. Also see @bio_alloc_bioset.

 *

 *   If %__GFP_WAIT is set, then bio_alloc will always be able to allocate

 *   a bio. This is due to the mempool guarantees. To make this work, callers

 *   must never allocate more than 1 bio at the time from this pool. Callers

 *   that need to allocate more than 1 bio must always submit the previously

 *   allocate bio for IO before attempting to allocate a new one. Failure to

 *   do so can cause livelocks under memory pressure.

 *

 **/

struct bio *bio_alloc(gfp_t gfp_mask, int nr_iovecs)

{

	struct bio *bio = bio_alloc_bioset(gfp_mask, nr_iovecs, fs_bio_set);