bio_alloc_bioset — allocate a bio for I/O
struct bio * bio_alloc_bioset ( | gfp_t gfp_mask, |
int nr_iovecs, | |
struct bio_set * bs) ; |
gfp_mask
the GFP_ mask given to the slab allocator
nr_iovecs
number of iovecs to pre-allocate
bs
the bio_set to allocate from.
If bs
is NULL, uses kmalloc
to allocate the bio; else the allocation is
backed by the bs
's mempool.
When bs
is not NULL, 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 deadlocks under memory pressure.