suse man page for bio_alloc

BIO_ALLOC(9)							   The Linux VFS						      BIO_ALLOC(9)

NAME
       bio_alloc - allocate a new bio, memory pool backed

SYNOPSIS
       struct bio * bio_alloc(gfp_t gfp_mask, int nr_iovecs);

ARGUMENTS
       gfp_mask
	   allocation mask to use

       nr_iovecs
	   number of iovecs

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 and bio_kmalloc.

       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 a time from this pool. Callers that need to allocate more than 1 bio must always submit the
       previously allocated bio for IO before attempting to allocate a new one. Failure to do so can cause livelocks under memory pressure.

RETURNS
       Pointer to new bio on success, NULL on failure.

COPYRIGHT
Kernel Hackers Manual 2.6.					     July 2010							      BIO_ALLOC(9)