ping?
On Wed, Jan 31, 2018 at 02:54:56AM -0800, Matthew Wilcox wrote:
> On Tue, Jan 30, 2018 at 11:26:42AM +1300, xen@xxxxxxxxxxxxxxxxxx wrote:
> > After, received this stack.
> >
> > Have not tried memtest86. These are production hosts. This has occurred on
> > multiple hosts. I can only recall this occurring on 32 bit kernels. I
> > cannot recall issues with other VMs not running that kernel on the same
> > hosts.
> >
> > [ 125.329163] Bad swp_entry: e000000
>
> Mixed news here then ... 'e' is 8 | 4 | 2, so it's not a single bitflip.
> So no point in running memtest86.
>
> I should have made the printk produce leading zeroes, because that's
> 0x0e00'0000. ptes use the top 5 bits to encode the swapfile, so
> this swap entry is decoded as swapfile 1, page number 0x0600'0000.
> That's clearly ludicrous because you don't have a swapfile 1, and if
> you did, it wouldn't be so large as a terabyte.
>
> I think the next step in debugging this is printing the PTE which gave
> us this swp_entry. If you can drop the patch I asked you to try, and
> apply this patch instead, we'll have more idea about what's going on.
>
> Thanks!
>
> diff --git a/mm/memory.c b/mm/memory.c
> index 403934297a3d..8caaddb07747 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -2892,6 +2892,10 @@ int do_swap_page(struct vm_fault *vmf)
> if (!page)
> page = lookup_swap_cache(entry, vma_readahead ? vma : NULL,
> vmf->address);
> + if (IS_ERR(page)) {
> + pte_ERROR(vmf->orig_pte);
> + page = NULL;
> + }
> if (!page) {
> struct swap_info_struct *si = swp_swap_info(entry);
>
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 7fbe67be86fa..905fa34e022a 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -1651,6 +1651,10 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
> if (swap.val) {
> /* Look it up and read it in.. */
> page = lookup_swap_cache(swap, NULL, 0);
> + if (IS_ERR(page)) {
> + pte_ERROR(vmf->orig_pte);
> + page = NULL;
> + }
> if (!page) {
> /* Or update major stats only when swapin succeeds?? */
> if (fault_type) {
> diff --git a/mm/swap_state.c b/mm/swap_state.c
> index 39ae7cfad90f..7ee594c8eadd 100644
> --- a/mm/swap_state.c
> +++ b/mm/swap_state.c
> @@ -334,8 +334,14 @@ struct page *lookup_swap_cache(swp_entry_t entry, struct vm_area_struct *vma,
> struct page *page;
> unsigned long ra_info;
> int win, hits, readahead;
> + struct address_space *swapper_space = swap_address_space(entry);
> +
> + if (!swapper_space) {
> + pr_err("Bad swp_entry: %lx\n", entry.val);
> + return ERR_PTR(-EFAULT);
> + }
>
> - page = find_get_page(swap_address_space(entry), swp_offset(entry));
> + page = find_get_page(swapper_space, swp_offset(entry));
>
> INC_CACHE_INFO(find_total);
> if (page) {
> @@ -676,6 +682,10 @@ struct page *swap_readahead_detect(struct vm_fault *vmf,
> if ((unlikely(non_swap_entry(entry))))
> return NULL;
> page = lookup_swap_cache(entry, vma, faddr);
> + if (IS_ERR(page)) {
> + pte_ERROR(vmf->orig_pte);
> + page = NULL;
> + }
> if (page)
> return page;
>
>
> --
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