Re: [PATCH] mm: fix trying to reclaim unevicable LRU page
From: Michal Hocko
Date: Mon Jun 10 2019 - 17:18:20 EST
On Mon 10-06-19 20:21:12, Minchan Kim wrote:
[...]
> >From 5cb8958ea240e2580bd2b331448009e8e1854240 Mon Sep 17 00:00:00 2001
> From: Minchan Kim <minchan@xxxxxxxxxx>
> Date: Fri, 24 May 2019 15:54:10 +0900
> Subject: [PATCH] mm: fix trying to reclaim unevicable LRU page
>
> There was below bugreport from Wu Fangsuo.
>
> In CMA allocation path, isolate_migratepages_range could isolate unevictable
> LRU pages and reclaim_clean_page_from_list can try to reclaim them if
> they are clean file-backed pages.
>
> 7200 [ 680.491097] c4 7125 (syz-executor) page:ffffffbf02f33b40 count:86 mapcount:84 mapping:ffffffc08fa7a810 index:0x24
> 7201 [ 680.531186] c4 7125 (syz-executor) flags: 0x19040c(referenced|uptodate|arch_1|mappedtodisk|unevictable|mlocked)
> 7202 [ 680.544987] c0 7125 (syz-executor) raw: 000000000019040c ffffffc08fa7a810 0000000000000024 0000005600000053
> 7203 [ 680.556162] c0 7125 (syz-executor) raw: ffffffc009b05b20 ffffffc009b05b20 0000000000000000 ffffffc09bf3ee80
> 7204 [ 680.566860] c0 7125 (syz-executor) page dumped because: VM_BUG_ON_PAGE(PageLRU(page) || PageUnevictable(page))
> 7205 [ 680.578038] c0 7125 (syz-executor) page->mem_cgroup:ffffffc09bf3ee80
> 7206 [ 680.585467] c0 7125 (syz-executor) ------------[ cut here ]------------
> 7207 [ 680.592466] c0 7125 (syz-executor) kernel BUG at /home/build/farmland/adroid9.0/kernel/linux/mm/vmscan.c:1350!
> 7223 [ 680.603663] c0 7125 (syz-executor) Internal error: Oops - BUG: 0 [#1] PREEMPT SMP
> 7224 [ 680.611436] c0 7125 (syz-executor) Modules linked in:
> 7225 [ 680.616769] c0 7125 (syz-executor) CPU: 0 PID: 7125 Comm: syz-executor Tainted: G S 4.14.81 #3
> 7226 [ 680.626826] c0 7125 (syz-executor) Hardware name: ASR AQUILAC EVB (DT)
> 7227 [ 680.633623] c0 7125 (syz-executor) task: ffffffc00a54cd00 task.stack: ffffffc009b00000
> 7228 [ 680.641917] c0 7125 (syz-executor) PC is at shrink_page_list+0x1998/0x3240
> 7229 [ 680.649144] c0 7125 (syz-executor) LR is at shrink_page_list+0x1998/0x3240
> 7230 [ 680.656303] c0 7125 (syz-executor) pc : [<ffffff90083a2158>] lr : [<ffffff90083a2158>] pstate: 60400045
> 7231 [ 680.666086] c0 7125 (syz-executor) sp : ffffffc009b05940
> ..
> 7342 [ 681.671308] c0 7125 (syz-executor) [<ffffff90083a2158>] shrink_page_list+0x1998/0x3240
> 7343 [ 681.679567] c0 7125 (syz-executor) [<ffffff90083a3dc0>] reclaim_clean_pages_from_list+0x3c0/0x4f0
> 7344 [ 681.688793] c0 7125 (syz-executor) [<ffffff900837ed64>] alloc_contig_range+0x3bc/0x650
> 7347 [ 681.717421] c0 7125 (syz-executor) [<ffffff90084925cc>] cma_alloc+0x214/0x668
> 7348 [ 681.724892] c0 7125 (syz-executor) [<ffffff90091e4d78>] ion_cma_allocate+0x98/0x1d8
> 7349 [ 681.732872] c0 7125 (syz-executor) [<ffffff90091e0b20>] ion_alloc+0x200/0x7e0
> 7350 [ 681.740302] c0 7125 (syz-executor) [<ffffff90091e154c>] ion_ioctl+0x18c/0x378
> 7351 [ 681.747738] c0 7125 (syz-executor) [<ffffff90084c6824>] do_vfs_ioctl+0x17c/0x1780
> 7352 [ 681.755514] c0 7125 (syz-executor) [<ffffff90084c7ed4>] SyS_ioctl+0xac/0xc0
>
> Wu found it's due to [1]. Before that, unevictable page goes to cull_mlocked
> routine so that it couldn't reach the VM_BUG_ON_PAGE line.
>
> To fix the issue, this patch filter out unevictable LRU pages
> from the reclaim_clean_pages_from_list in CMA.
>
> [1] ad6b67041a45, mm: remove SWAP_MLOCK in ttu
>
> Cc: <stable@xxxxxxxxxx> [4.12+]
> Reported-debugged-by: Wu Fangsuo <fangsuowu@xxxxxxxxxxxx>
> Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
OK, this looks better. Thanks!
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
> ---
> mm/vmscan.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index d9c3e873eca6..7350afae5c3c 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1505,7 +1505,7 @@ unsigned long reclaim_clean_pages_from_list(struct zone *zone,
>
> list_for_each_entry_safe(page, next, page_list, lru) {
> if (page_is_file_cache(page) && !PageDirty(page) &&
> - !__PageMovable(page)) {
> + !__PageMovable(page) && !PageUnevictable(page)) {
> ClearPageActive(page);
> list_move(&page->lru, &clean_pages);
> }
> --
> 2.22.0.rc2.383.gf4fbbf30c2-goog
>
--
Michal Hocko
SUSE Labs