mm: fix trying to reclaim unevictable lru page when calling madvise_p…

…ageout

Recently, I hit the following issue when running upstream.

  kernel BUG at mm/vmscan.c:1521!
  invalid opcode: 0000 [#1] SMP KASAN PTI
  CPU: 0 PID: 23385 Comm: syz-executor.6 Not tainted 5.4.0-rc4+ #1
  RIP: 0010:shrink_page_list+0x12b6/0x3530 mm/vmscan.c:1521
  Call Trace:
   reclaim_pages+0x499/0x800 mm/vmscan.c:2188
   madvise_cold_or_pageout_pte_range+0x58a/0x710 mm/madvise.c:453
   walk_pmd_range mm/pagewalk.c:53 [inline]
   walk_pud_range mm/pagewalk.c:112 [inline]
   walk_p4d_range mm/pagewalk.c:139 [inline]
   walk_pgd_range mm/pagewalk.c:166 [inline]
   __walk_page_range+0x45a/0xc20 mm/pagewalk.c:261
   walk_page_range+0x179/0x310 mm/pagewalk.c:349
   madvise_pageout_page_range mm/madvise.c:506 [inline]
   madvise_pageout+0x1f0/0x330 mm/madvise.c:542
   madvise_vma mm/madvise.c:931 [inline]
   __do_sys_madvise+0x7d2/0x1600 mm/madvise.c:1113
   do_syscall_64+0x9f/0x4c0 arch/x86/entry/common.c:290
   entry_SYSCALL_64_after_hwframe+0x49/0xbe

madvise_pageout() accesses the specified range of the vma and isolates
them, then runs shrink_page_list() to reclaim its memory.  But it also
isolates the unevictable pages to reclaim.  Hence, we can catch the
cases in shrink_page_list().

The root cause is that we scan the page tables instead of specific LRU
list.  and so we need to filter out the unevictable lru pages from our
end.

Link: http://lkml.kernel.org/r/[email protected]
Fixes: 1a4e58c ("mm: introduce MADV_PAGEOUT")
Signed-off-by: zhong jiang <[email protected]>
Suggested-by: Johannes Weiner <[email protected]>
Acked-by: Johannes Weiner <[email protected]>
Acked-by: Minchan Kim <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

mm/madvise.c

@@ -363,8 +363,12 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd,
 		ClearPageReferenced(page);
 		test_and_clear_page_young(page);
 		if (pageout) {
-			if (!isolate_lru_page(page))
-				list_add(&page->lru, &page_list);
+			if (!isolate_lru_page(page)) {
+				if (PageUnevictable(page))
+					putback_lru_page(page);
+				else
+					list_add(&page->lru, &page_list);
+			}
 		} else
 			deactivate_page(page);
 huge_unlock:
@@ -441,8 +445,12 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd,
 		ClearPageReferenced(page);
 		test_and_clear_page_young(page);
 		if (pageout) {
-			if (!isolate_lru_page(page))
-				list_add(&page->lru, &page_list);
+			if (!isolate_lru_page(page)) {
+				if (PageUnevictable(page))
+					putback_lru_page(page);
+				else
+					list_add(&page->lru, &page_list);
+			}
 		} else
 			deactivate_page(page);
 	}