On Wed, Dec 21, 2016 at 02:22:01PM +0100, Michal Hocko wrote: >On Wed 21-12-16 13:13:32, Wei Yang wrote: >> On Wed, Dec 21, 2016 at 08:51:16AM +0100, Michal Hocko wrote: >> >On Tue 20-12-16 16:48:23, Wei Yang wrote: >> >> On Mon, Dec 19, 2016 at 04:21:57PM +0100, Michal Hocko wrote: >> >> >On Sun 18-12-16 14:47:50, Wei Yang wrote: >> >> >> memblock_reserve() may fail in case there is not enough regions. >> >> > >> >> >Have you seen this happenning in the real setups or this is a by-review >> >> >driven change? >> >> >> >> This is a by-review driven change. >> >> >> >> >[...] >> >> >> again: >> >> >> alloc = memblock_find_in_range_node(size, align, min_addr, max_addr, >> >> >> nid, flags); >> >> >> - if (alloc) >> >> >> + if (alloc && !memblock_reserve(alloc, size)) >> >> >> goto done; >> > >> >So how exactly does the reserve fail when memblock_find_in_range_node >> >found a suitable range for the given size? >> > >> >> Even memblock_find_in_range_node() gets a suitable range, memblock_reserve() >> still could fail. And the case just happens when memblock can't resize. >> memblock_reserve() reserve a range by adding a range to memblock.reserved. In >> case the memblock.reserved is full and can't resize, this fails. > >Sorry for being dense but what does it mean that the reserved will get >full? Also how probable is such a situation? Is it even real? In other >words does this fix a real or only a theoretical problem? > This is a theoretical problem. While if happens, it is hard to detect. Future allocator will think this range is still available. >Anyway this all should be part of the changelog. Ok, let me add this in changelog in next version. >-- >Michal Hocko >SUSE Labs -- Wei Yang Help you, Help me -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>