Re: [PATCH v5 0/6] Fix some bugs related to ramp and dax

[Muchun Song]

On Fri, Apr 1, 2022 at 11:44 AM Muchun Song <songmuchun@xxxxxxxxxxxxx> wrote:
>
> On Thu, Mar 31, 2022 at 11:55 PM Qian Cai <quic_qiancai@xxxxxxxxxxx> wrote:
> >
> > On Fri, Mar 18, 2022 at 03:45:23PM +0800, Muchun Song wrote:
> > > This series is based on next-20220225.
> > >
> > > Patch 1-2 fix a cache flush bug, because subsequent patches depend on
> > > those on those changes, there are placed in this series.  Patch 3-4
> > > are preparation for fixing a dax bug in patch 5.  Patch 6 is code cleanup
> > > since the previous patch remove the usage of follow_invalidate_pte().
> >
> > Reverting this series fixed boot crashes.
> >
> >  KASAN: null-ptr-deref in range [0x0000000000000018-0x000000000000001f]
> >  Mem abort info:
> >    ESR = 0x96000004
> >    EC = 0x25: DABT (current EL), IL = 32 bits
> >    SET = 0, FnV = 0
> >    EA = 0, S1PTW = 0
> >    FSC = 0x04: level 0 translation fault
> >  Data abort info:
> >    ISV = 0, ISS = 0x00000004
> >    CM = 0, WnR = 0
> >  [dfff800000000003] address between user and kernel address ranges
> >  Internal error: Oops: 96000004 [#1] PREEMPT SMP
> >  Modules linked in: cdc_ether usbnet ipmi_devintf ipmi_msghandler cppc_cpufreq fuse ip_tables x_tables ipv6 btrfs blake2b_generic libcrc32c xor xor_neon raid6_pq zstd_compress dm_mod nouveau crct10dif_ce drm_ttm_helper mlx5_core ttm drm_dp_helper drm_kms_helper nvme mpt3sas nvme_core xhci_pci raid_class drm xhci_pci_renesas
> >  CPU: 3 PID: 1707 Comm: systemd-udevd Not tainted 5.17.0-next-20220331-00004-g2d550916a6b9 #51
> >  pstate: 104000c9 (nzcV daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> >  pc : __lock_acquire
> >  lr : lock_acquire.part.0
> >  sp : ffff800030a16fd0
> >  x29: ffff800030a16fd0 x28: ffffdd876c4e9f90 x27: 0000000000000018
> >  x26: 0000000000000000 x25: 0000000000000018 x24: 0000000000000000
> >  x23: ffff08022beacf00 x22: ffffdd8772507660 x21: 0000000000000000
> >  x20: 0000000000000000 x19: 0000000000000000 x18: ffffdd8772417d2c
> >  x17: ffffdd876c5bc2e0 x16: 1fffe100457d5b06 x15: 0000000000000094
> >  x14: 000000000000f1f1 x13: 00000000f3f3f3f3 x12: ffff08022beacf08
> >  x11: 1ffffbb0ee482fa5 x10: ffffdd8772417d28 x9 : 0000000000000000
> >  x8 : 0000000000000003 x7 : ffffdd876c4e9f90 x6 : 0000000000000000
> >  x5 : 0000000000000000 x4 : 0000000000000001 x3 : 0000000000000000
> >  x2 : 0000000000000000 x1 : 0000000000000003 x0 : dfff800000000000
> >  Call trace:
> >   __lock_acquire
> >   lock_acquire.part.0
> >   lock_acquire
> >   _raw_spin_lock
> >   page_vma_mapped_walk
> >   try_to_migrate_one
> >   rmap_walk_anon
> >   try_to_migrate
> >   __unmap_and_move
> >   unmap_and_move
> >   migrate_pages
> >   migrate_misplaced_page
> >   do_huge_pmd_numa_page
> >   __handle_mm_fault
> >   handle_mm_fault
> >   do_translation_fault
> >   do_mem_abort
> >   el0_da
> >   el0t_64_sync_handler
> >   el0t_64_sync
> >  Code: d65f03c0 d343ff61 d2d00000 f2fbffe0 (38e06820)
> >  ---[ end trace 0000000000000000 ]---
> >  Kernel panic - not syncing: Oops: Fatal exception
> >  SMP: stopping secondary CPUs
> >  Kernel Offset: 0x5d8763da0000 from 0xffff800008000000
> >  PHYS_OFFSET: 0x80000000
> >  CPU features: 0x000,00085c0d,19801c82
> >  Memory Limit: none
> >  ---[ end Kernel panic - not syncing: Oops: Fatal exception ]---
>
> Thanks for your report. Would you mind providing the .config?

Hi Qian Cai,

Would you mind helping me test if the following patch works properly?
Thanks.

diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index b3bf802a6435..3da82bf65de8 100644
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c
@@ -210,7 +210,8 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
                 */
                pmde = READ_ONCE(*pvmw->pmd);

-               if (pmd_leaf(pmde) || is_pmd_migration_entry(pmde)) {
+               if (pmd_trans_huge(pmde) || is_pmd_migration_entry(pmde) ||
+                   (pmd_present(pmde) && pmd_devmap(pmde))) {
                        pvmw->ptl = pmd_lock(mm, pvmw->pmd);
                        pmde = *pvmw->pmd;
                        if (!pmd_present(pmde)) {