On Thu, Aug 04, 2016 at 09:59:17PM +0100, James Hogan wrote: > > Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> > > Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx> > > Acked-by: Vlastimil Babka <vbabka@xxxxxxx> > > This breaks boot on metag architecture: > Oops: err 0007 (Data access general read/write fault) addr 00233008 [#1] > > It appears to be in node_page_state_snapshot() (via > pgdat_reclaimable()), and have come via mm_init. Here's the relevant > bit of the backtrace: > > node_page_state_snapshot@0x4009c884(enum node_stat_item item = > ???, struct pglist_data * pgdat = ???) + 0x48 > pgdat_reclaimable(struct pglist_data * pgdat = 0x402517a0) > show_free_areas(unsigned int filter = 0) + 0x2cc > show_mem(unsigned int filter = 0) + 0x18 > mm_init@0x4025c3d4() > start_kernel() + 0x204 > > __per_cpu_offset[0] == 0x233000 (close to bad addr), > pgdat->per_cpu_nodestats = NULL. and setup_per_cpu_pageset() > definitely hasn't been called yet (mm_init is called before > setup_per_cpu_pageset()). > > Any ideas what the correct solution is (and why presumably others > haven't seen the same issue on other architectures?). > metag calls show_mem in mem_init() before the pagesets are initialised. What's surprising is that it worked for the zone stats as it appears that calling zone_reclaimable() from that context should also have broken. Did anything change recently that would have avoided the zone->pageset dereference in zone_reclaimable() before? The easiest option would be to not call show_mem from arch code until after the pagesets are setup. -- Mel Gorman SUSE Labs -- 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>