On Tue, 2013-08-27 at 17:37 +0800, Tang Chen wrote:memblock_alloc_base_nid() is a common API of memblock. And it calls
memblock_find_in_range_node() with %start = 0, which means it has no
limit for the lowest address by default.
memblock_find_in_range_node(0, max_addr, size, align, nid);
Since we introduced current_limit_low to memblock, if we have no limit
for the lowest address or we are not sure, we should pass
MEMBLOCK_ALLOC_ACCESSIBLE to %start so that it will be limited by the
default low limit.
dma_contiguous_reserve() and setup_log_buf() will eventually call
memblock_alloc_base_nid() to allocate memory. So if the allocation order
is from low to high, they will allocate memory from the lowest limit
to higher memory.
This requires the callers to use MEMBLOCK_ALLOC_ACCESSIBLE instead of 0.
Is there a good way to make sure that all callers will follow this rule
going forward? Perhaps, memblock_find_in_range_node() should emit some
message if 0 is passed when current_order is low to high and the boot
option is specified?
Similarly, I wonder if we should have a check to the allocation size to
make sure that all allocations will stay small in this case.