From b9705d8778e7adc97de38f405f835a2426e14d84 Mon Sep 17 00:00:00 2001 From: Juergen Gross Date: Thu, 4 Jul 2019 15:14:36 -0700 Subject: mm/page_alloc.c: fix regression with deferred struct page init Commit 0e56acae4b4d ("mm: initialize MAX_ORDER_NR_PAGES at a time instead of doing larger sections") is causing a regression on some systems when the kernel is booted as Xen dom0. The system will just hang in early boot. Reason is an endless loop in get_page_from_freelist() in case the first zone looked at has no free memory. deferred_grow_zone() is always returning true due to the following code snipplet: /* If the zone is empty somebody else may have cleared out the zone */ if (!deferred_init_mem_pfn_range_in_zone(&i, zone, &spfn, &epfn, first_deferred_pfn)) { pgdat->first_deferred_pfn = ULONG_MAX; pgdat_resize_unlock(pgdat, &flags); return true; } This in turn results in the loop as get_page_from_freelist() is assuming forward progress can be made by doing some more struct page initialization. Link: http://lkml.kernel.org/r/20190620160821.4210-1-jgross@suse.com Fixes: 0e56acae4b4d ("mm: initialize MAX_ORDER_NR_PAGES at a time instead of doing larger sections") Signed-off-by: Juergen Gross Suggested-by: Alexander Duyck Acked-by: Alexander Duyck Cc: Michal Hocko Cc: Pavel Tatashin Cc: Mike Rapoport Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/page_alloc.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index d66bc8abe0af..8e3bc949ebcc 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1826,7 +1826,8 @@ deferred_grow_zone(struct zone *zone, unsigned int order) first_deferred_pfn)) { pgdat->first_deferred_pfn = ULONG_MAX; pgdat_resize_unlock(pgdat, &flags); - return true; + /* Retry only once. */ + return first_deferred_pfn != ULONG_MAX; } /* -- cgit