afs_do_lookup() will do an order-1 allocation to allocate status records if
there are more than 39 vnodes to stat.
Fix this by allocating an array of {status,callback} records for each vnode
we want to examine using vmalloc() if larger than a page.
This not only gets rid of the order-1 allocation, but makes it easier to
grow beyond 50 records for YFS servers. It also allows us to move to
{status,callback} tuples for other calls too and makes it easier to lock
across the application of the status and the callback to the vnode.
Fixes: 5cf9dd55a0 ("afs: Prospectively look up extra files when doing a single lookup")
Signed-off-by: David Howells <dhowells@redhat.com>
87182759cd