From: Minchan Kim minchan@kernel.org Subject: mm/vmscan.c: fix trying to reclaim unevictable LRU page

There was the below bug report from Wu Fangsuo.

On the 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 ad6b67041a45 ("mm: remove SWAP_MLOCK in ttu"). Before that, unevictable pages go to cull_mlocked so that we can't reach the VM_BUG_ON_PAGE line.

To fix the issue, this patch filters out unevictable LRU pages from the reclaim_clean_pages_from_list in CMA.

Link: http://lkml.kernel.org/r/20190524071114.74202-1-minchan@kernel.org Fixes: ad6b67041a45 ("mm: remove SWAP_MLOCK in ttu") Signed-off-by: Minchan Kim minchan@kernel.org Reported-by: Wu Fangsuo fangsuowu@asrmicro.com Debugged-by: Wu Fangsuo fangsuowu@asrmicro.com Tested-by: Wu Fangsuo fangsuowu@asrmicro.com Reviewed-by: Andrew Morton akpm@linux-foundation.org Acked-by: Michal Hocko mhocko@suse.com Cc: Pankaj Suryawanshi pankaj.suryawanshi@einfochips.com Cc: stable@vger.kernel.org [4.12+] Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/vmscan.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/vmscan.c~mm-fix-trying-to-reclaim-unevicable-lru-page +++ a/mm/vmscan.c @@ -1505,7 +1505,7 @@ unsigned long reclaim_clean_pages_from_l

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); } _