On 12/29/2015 01:07 PM, Heiko Carstens wrote:
mod_zone_page_state() takes a "delta" integer argument. delta contains the number of pages that should be added or subtracted from a struct zone's vm_stat field. If a zone is larger than 8TB this will cause overflows. E.g. for a zone with a size slightly larger than 8TB the line mod_zone_page_state(zone, NR_ALLOC_BATCH, zone->managed_pages); in mm/page_alloc.c:free_area_init_core() will result in a negative result for the NR_ALLOC_BATCH entry within the zone's vm_stat, since 8TB contain 0x8xxxxxxx pages which will be sign extended to a negative value. Fix this by changing the delta argument to long type. This could fix an early boot problem seen on s390, where we have a 9TB system with only one node. ZONE_DMA contains 2GB and ZONE_NORMAL the rest. The system is trying to allocate a GFP_DMA page but ZONE_DMA is completely empty, so it tries to reclaim pages in an endless loop. This was seen on a heavily patched 3.10 kernel. One possible explaination seem to be the overflows caused by mod_zone_page_state(). Unfortunately I did not have the chance to verify that this patch actually fixes the problem, since I don't have access to the system right now. However the overflow problem does exist anyway. Given the description that a system with slightly less than 8TB does work, this seems to be a candidate for the observed problem. Signed-off-by: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx> -- 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>