In fast_isolate_freepages, high_pfn will be used if a prefered one(PFN >= low_fn) not found. But the high_pfn is not reset before searching an free area, so when it was used as freepage, it may from another free area searched before. And move_freelist_head(freelist, freepage) will have unexpected behavior(eg. corrupt the MOVABLE freelist) Unable to handle kernel paging request at virtual address dead000000000200 Mem abort info: ESR = 0x96000044 Exception class = DABT (current EL), IL = 32 bits SET = 0, FnV = 0 EA = 0, S1PTW = 0 Data abort info: ISV = 0, ISS = 0x00000044 CM = 0, WnR = 1 [dead000000000200] address between user and kernel address ranges -000|list_cut_before(inline) -000|move_freelist_head(inline) -000|fast_isolate_freepages(inline) -000|isolate_freepages(inline) -000|compaction_alloc(?, ?) -001|unmap_and_move(inline) -001|migrate_pages([NSD:0xFFFFFF80088CBBD0] from = 0xFFFFFF80088CBD88, [NSD:0xFFFFFF80088CBBC8] get_new_p -002|__read_once_size(inline) -002|static_key_count(inline) -002|static_key_false(inline) -002|trace_mm_compaction_migratepages(inline) -002|compact_zone(?, [NSD:0xFFFFFF80088CBCB0] capc = 0x0) -003|kcompactd_do_work(inline) -003|kcompactd([X19] p = 0xFFFFFF93227FBC40) -004|kthread([X20] _create = 0xFFFFFFE1AFB26380) -005|ret_from_fork(asm) ---|end of frame The issue was reported on an smart phone product with 6GB ram and 3GB zram as swap device. This patch fixes the issue by reset high_pfn before searching each free area, which ensure freepage and freelist match when call move_freelist_head in fast_isolate_freepages(). Link: http://lkml.kernel.org/r/20190118175136.31341-12-mgorman@xxxxxxxxxxxxxxxxxxx Fixes: 5a811889de10f1eb ("mm, compaction: use free lists to quickly locate a migration target") --- mm/compaction.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/compaction.c b/mm/compaction.c index cc1a7f600a86..75f0e550b18f 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -1303,7 +1303,7 @@ fast_isolate_freepages(struct compact_control *cc) { unsigned int limit = min(1U, freelist_scan_limit(cc) >> 1); unsigned int nr_scanned = 0; - unsigned long low_pfn, min_pfn, high_pfn = 0, highest = 0; + unsigned long low_pfn, min_pfn, highest = 0; unsigned long nr_isolated = 0; unsigned long distance; struct page *page = NULL; @@ -1348,6 +1348,7 @@ fast_isolate_freepages(struct compact_control *cc) struct page *freepage; unsigned long flags; unsigned int order_scanned = 0; + unsigned long high_pfn = 0; if (!area->nr_free) continue; -- 2.25.1
