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?
