On 2022/5/25 6:10, Andrew Morton wrote: > On Sat, 21 May 2022 17:34:28 +0800 Miaohe Lin <linmiaohe@xxxxxxxxxx> wrote: > >> On 2022/5/20 14:34, HORIGUCHI NAOYA(堀口 直也) wrote: >>> On Thu, May 19, 2022 at 08:50:29PM +0800, Miaohe Lin wrote: >>>> When swap in shmem error at swapoff time, there would be a infinite loop >>>> in the while loop in shmem_unuse_inode(). It's because swapin error is >>>> deliberately ignored now and thus info->swapped will never reach 0. So >>>> we can't escape the loop in shmem_unuse(). >>>> >>>> In order to fix the issue, swapin_error entry is stored in the mapping >>>> when swapin error occurs. So the swapcache page can be freed and the >>>> user won't end up with a permanently mounted swap because a sector is >>>> bad. If the page is accessed later, the user process will be killed >>>> so that corrupted data is never consumed. On the other hand, if the >>>> page is never accessed, the user won't even notice it. >>>> >>>> Reported-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx> >>>> Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx> >>> >>> Hi Miaohe, >>> >>> Thank you for the update. I might miss something, but I still see the same >>> problem (I checked it on mm-everything-2022-05-19-00-03 + this patchset). >> >> Hi Naoya, >> I reproduce the issue in the linux-next-next-20220520 version. And I found even if >> I *do not inject the swapin error*, the deadloop still occurs. After investigating the >> code for a long while, I found the root cause: >> >> diff --git a/mm/shmem.c b/mm/shmem.c >> index d55dd972023a..6d23ed4d23cb 100644 >> --- a/mm/shmem.c >> +++ b/mm/shmem.c >> @@ -1182,7 +1182,7 @@ static int shmem_find_swap_entries(struct address_space *mapping, >> if (swp_type(entry) != type) >> continue; >> >> - indices[ret] = xas.xa_index; >> + indices[ret++] = xas.xa_index; >> if (!folio_batch_add(fbatch, folio)) >> break; >> >> The origin code does not increment the ret value when a folio is found. I will send a patch >> to fix this next week. Thanks! :) > > So I'm thinking that with Hugh's "mm/shmem: fix shmem folio swapoff > hang", this patchset is now looking OK, so > > mm-swapfile-unuse_pte-can-map-random-data-if-swap-read-fails.patch > mm-swapfile-fix-lost-swap-bits-in-unuse_pte.patch > mm-madvise-free-hwpoison-and-swapin-error-entry-in-madvise_free_pte_range.patch > mm-shmem-fix-infinite-loop-when-swap-in-shmem-error-at-swapoff-time.patch > mm-filter-out-swapin-error-entry-in-shmem-mapping.patch > # > > are OK for merging into mainline? I think so. But it might be better to have Acked-by or Reviewed-by tag for [PATCH v4 4/5] first. :) Thanks! > . >
