On Fri, Aug 26, 2022 at 11:20:58AM +0800, Yin, Fengwei wrote: > > > On 8/26/2022 2:46 AM, Matthew Wilcox wrote: > >>> Looks like my analysis from yesterday was dropped: > >>> > >>> : This all seems quite plausible. The reproducer seems to (correct me > >>> : if I'm wrong) create an AF_PACKET socket and mmap it. af_packet.c > >>> : seems to create compound pages and mmap them. This isn't folio-related > >>> : at all; I just moved the code that warns about it from mm/vmscan.c to > >>> : folio-compat.c. > >>> : > >>> : Looks like a long-standing bug in MADV_PAGEOUT to me. > >> Such page should never be on lru, right? We could test lru before > >> calling isolate_lru_page() for this case? I know isolate_lru_page() > >> does the check, but the tail page warning is raised before the check. > >> > >> Could the tail page warning be moved under the lru flag test? Seems > >> possible, but it should need extra handling (re-set lru flag). Seems a > >> little bit overkilling. > > There's a number of ways of solving this. I'm interested in seeing > > which one Minchan thinks is best. > > > > My understanding is: > PageTransCompound() return false for compound page if THP is disabled > in kernel config. Replacing PageTransCompound() with PageCompound() > could work here. But for the long term, folio should be the answer. :). Thanks for reporting and analysis, folks, I agree with Yang since the MADV_PAGEOUT should work with only LRU pages. >From 0a43ac31c903bc23299a868a6d6724ff5b807e3d Mon Sep 17 00:00:00 2001 From: Minchan Kim <minchan@xxxxxxxxxx> Date: Fri, 26 Aug 2022 09:37:34 -0700 Subject: [PATCH] mm: fix madivse_pageout mishandling on non-LRU page MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit MADV_PAGEOUT tries to isolate non-LRU pages and get the warning from isolate_lru_page below. Fix it with checking PageLRU in advance. ------------[ cut here ]------------ trying to isolate tail page WARNING: CPU: 0 PID: 6175 at mm/folio-compat.c:158 isolate_lru_page+0x130/0x140 Modules linked in: CPU: 0 PID: 6175 Comm: syz-executor.0 Not tainted 5.18.12 #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014 RIP: 0010:isolate_lru_page+0x130/0x140 Link: https://lore.kernel.org/linux-mm/485f8c33.2471b.182d5726afb.Coremail.hantianshuo@xxxxxxxxx/ Reported-by: 韩天硕 <hantianshuo@xxxxxxxxx> Suggested-by: Yang Shi <shy828301@xxxxxxxxx> Fixes: 1a4e58cce84e ("mm: introduce MADV_PAGEOUT") Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx> --- mm/madvise.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/mm/madvise.c b/mm/madvise.c index 682e1d161aef..a3fc4cd32ed3 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -452,8 +452,11 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd, continue; } - /* Do not interfere with other mappings of this page */ - if (page_mapcount(page) != 1) + /* + * Do not interfere with other mappings of this page and + * non-LRU page. + */ + if (!PageLRU(page) || page_mapcount(page) != 1) continue; VM_BUG_ON_PAGE(PageTransCompound(page), page); -- 2.37.2.672.g94769d06f0-goog
