On 1/12/21 10:47 AM, Rokudo Yan wrote: > 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") Sounds serious enough. Wonder how it wasn't reported sooner. Cc: <stable@xxxxxxxxxxxxxxx> Acked-by: Vlastimil Babka <vbabka@xxxxxxx> > --- > 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; >
