When the kernel copy a page from ksm_might_need_to_copy(), but runs
into an uncorrectable error, it will crash since poisoned page is
consumed by kernel, this is similar to Copy-on-write poison recovery,
When an error is detected during the page copy, return VM_FAULT_HWPOISON,
which help us to avoid system crash. Note, memory failure on a KSM
page will be skipped, but still call memory_failure_queue() to be
consistent with general memory failure process.
Signed-off-by: Kefeng Wang <[email protected]>
---
mm/ksm.c | 8 ++++++--
mm/memory.c | 3 +++
mm/swapfile.c | 2 +-
3 files changed, 10 insertions(+), 3 deletions(-)
diff --git a/mm/ksm.c b/mm/ksm.c
index dd02780c387f..83e2f74ae7da 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -2629,8 +2629,12 @@ struct page *ksm_might_need_to_copy(struct page *page,
new_page = NULL;
}
if (new_page) {
- copy_user_highpage(new_page, page, address, vma);
-
+ if (copy_mc_user_highpage(new_page, page, address, vma)) {
+ put_page(new_page);
+ new_page = ERR_PTR(-EHWPOISON);
+ memory_failure_queue(page_to_pfn(page), 0);
+ return new_page;
+ }
SetPageDirty(new_page);
__SetPageUptodate(new_page);
__SetPageLocked(new_page);
diff --git a/mm/memory.c b/mm/memory.c
index aad226daf41b..8711488f5305 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3840,6 +3840,9 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
if (unlikely(!page)) {
ret = VM_FAULT_OOM;
goto out_page;
+ } els if (unlikely(PTR_ERR(page) == -EHWPOISON)) {
+ ret = VM_FAULT_HWPOISON;
+ goto out_page;
}
folio = page_folio(page);
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 908a529bca12..d479811bc311 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1767,7 +1767,7 @@ static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
swapcache = page;
page = ksm_might_need_to_copy(page, vma, addr);
- if (unlikely(!page))
+ if (IS_ERR_OR_NULL(page))
return -ENOMEM;
pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
--
2.35.3
When the kernel copy a page from ksm_might_need_to_copy(), but runs
into an uncorrectable error, it will crash since poisoned page is
consumed by kernel, this is similar to Copy-on-write poison recovery,
When an error is detected during the page copy, return VM_FAULT_HWPOISON,
which help us to avoid system crash. Note, memory failure on a KSM
page will be skipped, but still call memory_failure_queue() to be
consistent with general memory failure process.
Signed-off-by: Kefeng Wang <[email protected]>
---
v2: fix type error
mm/ksm.c | 8 ++++++--
mm/memory.c | 3 +++
mm/swapfile.c | 2 +-
3 files changed, 10 insertions(+), 3 deletions(-)
diff --git a/mm/ksm.c b/mm/ksm.c
index dd02780c387f..83e2f74ae7da 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -2629,8 +2629,12 @@ struct page *ksm_might_need_to_copy(struct page *page,
new_page = NULL;
}
if (new_page) {
- copy_user_highpage(new_page, page, address, vma);
-
+ if (copy_mc_user_highpage(new_page, page, address, vma)) {
+ put_page(new_page);
+ new_page = ERR_PTR(-EHWPOISON);
+ memory_failure_queue(page_to_pfn(page), 0);
+ return new_page;
+ }
SetPageDirty(new_page);
__SetPageUptodate(new_page);
__SetPageLocked(new_page);
diff --git a/mm/memory.c b/mm/memory.c
index aad226daf41b..5b2c137dfb2a 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3840,6 +3840,9 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
if (unlikely(!page)) {
ret = VM_FAULT_OOM;
goto out_page;
+ } else if (unlikely(PTR_ERR(page) == -EHWPOISON)) {
+ ret = VM_FAULT_HWPOISON;
+ goto out_page;
}
folio = page_folio(page);
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 908a529bca12..d479811bc311 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1767,7 +1767,7 @@ static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
swapcache = page;
page = ksm_might_need_to_copy(page, vma, addr);
- if (unlikely(!page))
+ if (IS_ERR_OR_NULL(page))
return -ENOMEM;
pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
--
2.35.3
Hi Kefeng,
Thank you for the patch! Yet something to improve:
[auto build test ERROR on akpm-mm/mm-everything]
url: https://github.com/intel-lab-lkp/linux/commits/Kefeng-Wang/mm-hwposion-support-recovery-from-ksm_might_need_to_copy/20221209-095943
base: https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link: https://lore.kernel.org/r/20221209021525.196276-1-wangkefeng.wang%40huawei.com
patch subject: [PATCH -next resend] mm: hwposion: support recovery from ksm_might_need_to_copy()
config: hexagon-randconfig-r041-20221207
compiler: clang version 16.0.0 (https://github.com/llvm/llvm-project 6e4cea55f0d1104408b26ac574566a0e4de48036)
reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# https://github.com/intel-lab-lkp/linux/commit/503dfb85dafae7b3b09b7d6b29bb675fc7673a32
git remote add linux-review https://github.com/intel-lab-lkp/linux
git fetch --no-tags linux-review Kefeng-Wang/mm-hwposion-support-recovery-from-ksm_might_need_to_copy/20221209-095943
git checkout 503dfb85dafae7b3b09b7d6b29bb675fc7673a32
# save the config file
mkdir build_dir && cp config build_dir/.config
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=hexagon SHELL=/bin/bash
If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <[email protected]>
All errors (new ones prefixed by >>):
In file included from mm/memory.c:42:
In file included from include/linux/kernel_stat.h:9:
In file included from include/linux/interrupt.h:11:
In file included from include/linux/hardirq.h:11:
In file included from ./arch/hexagon/include/generated/asm/hardirq.h:1:
In file included from include/asm-generic/hardirq.h:17:
In file included from include/linux/irq.h:20:
In file included from include/linux/io.h:13:
In file included from arch/hexagon/include/asm/io.h:334:
include/asm-generic/io.h:547:31: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
val = __raw_readb(PCI_IOBASE + addr);
~~~~~~~~~~ ^
include/asm-generic/io.h:560:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
val = __le16_to_cpu((__le16 __force)__raw_readw(PCI_IOBASE + addr));
~~~~~~~~~~ ^
include/uapi/linux/byteorder/little_endian.h:37:51: note: expanded from macro '__le16_to_cpu'
#define __le16_to_cpu(x) ((__force __u16)(__le16)(x))
^
In file included from mm/memory.c:42:
In file included from include/linux/kernel_stat.h:9:
In file included from include/linux/interrupt.h:11:
In file included from include/linux/hardirq.h:11:
In file included from ./arch/hexagon/include/generated/asm/hardirq.h:1:
In file included from include/asm-generic/hardirq.h:17:
In file included from include/linux/irq.h:20:
In file included from include/linux/io.h:13:
In file included from arch/hexagon/include/asm/io.h:334:
include/asm-generic/io.h:573:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
val = __le32_to_cpu((__le32 __force)__raw_readl(PCI_IOBASE + addr));
~~~~~~~~~~ ^
include/uapi/linux/byteorder/little_endian.h:35:51: note: expanded from macro '__le32_to_cpu'
#define __le32_to_cpu(x) ((__force __u32)(__le32)(x))
^
In file included from mm/memory.c:42:
In file included from include/linux/kernel_stat.h:9:
In file included from include/linux/interrupt.h:11:
In file included from include/linux/hardirq.h:11:
In file included from ./arch/hexagon/include/generated/asm/hardirq.h:1:
In file included from include/asm-generic/hardirq.h:17:
In file included from include/linux/irq.h:20:
In file included from include/linux/io.h:13:
In file included from arch/hexagon/include/asm/io.h:334:
include/asm-generic/io.h:584:33: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
__raw_writeb(value, PCI_IOBASE + addr);
~~~~~~~~~~ ^
include/asm-generic/io.h:594:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
__raw_writew((u16 __force)cpu_to_le16(value), PCI_IOBASE + addr);
~~~~~~~~~~ ^
include/asm-generic/io.h:604:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
__raw_writel((u32 __force)cpu_to_le32(value), PCI_IOBASE + addr);
~~~~~~~~~~ ^
>> mm/memory.c:3843:5: error: use of undeclared identifier 'els'; did you mean 'fls'?
} els if (unlikely(PTR_ERR(page) == -EHWPOISON)) {
^~~
fls
arch/hexagon/include/asm/bitops.h:220:19: note: 'fls' declared here
static inline int fls(unsigned int x)
^
>> mm/memory.c:3843:8: error: expected ';' after expression
} els if (unlikely(PTR_ERR(page) == -EHWPOISON)) {
^
;
mm/memory.c:3843:5: warning: expression result unused [-Wunused-value]
} els if (unlikely(PTR_ERR(page) == -EHWPOISON)) {
^~~
7 warnings and 2 errors generated.
vim +3843 mm/memory.c
3680
3681 /*
3682 * We enter with non-exclusive mmap_lock (to exclude vma changes,
3683 * but allow concurrent faults), and pte mapped but not yet locked.
3684 * We return with pte unmapped and unlocked.
3685 *
3686 * We return with the mmap_lock locked or unlocked in the same cases
3687 * as does filemap_fault().
3688 */
3689 vm_fault_t do_swap_page(struct vm_fault *vmf)
3690 {
3691 struct vm_area_struct *vma = vmf->vma;
3692 struct folio *swapcache, *folio = NULL;
3693 struct page *page;
3694 struct swap_info_struct *si = NULL;
3695 rmap_t rmap_flags = RMAP_NONE;
3696 bool exclusive = false;
3697 swp_entry_t entry;
3698 pte_t pte;
3699 int locked;
3700 vm_fault_t ret = 0;
3701 void *shadow = NULL;
3702
3703 if (!pte_unmap_same(vmf))
3704 goto out;
3705
3706 entry = pte_to_swp_entry(vmf->orig_pte);
3707 if (unlikely(non_swap_entry(entry))) {
3708 if (is_migration_entry(entry)) {
3709 migration_entry_wait(vma->vm_mm, vmf->pmd,
3710 vmf->address);
3711 } else if (is_device_exclusive_entry(entry)) {
3712 vmf->page = pfn_swap_entry_to_page(entry);
3713 ret = remove_device_exclusive_entry(vmf);
3714 } else if (is_device_private_entry(entry)) {
3715 vmf->page = pfn_swap_entry_to_page(entry);
3716 vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd,
3717 vmf->address, &vmf->ptl);
3718 if (unlikely(!pte_same(*vmf->pte, vmf->orig_pte))) {
3719 spin_unlock(vmf->ptl);
3720 goto out;
3721 }
3722
3723 /*
3724 * Get a page reference while we know the page can't be
3725 * freed.
3726 */
3727 get_page(vmf->page);
3728 pte_unmap_unlock(vmf->pte, vmf->ptl);
3729 ret = vmf->page->pgmap->ops->migrate_to_ram(vmf);
3730 put_page(vmf->page);
3731 } else if (is_hwpoison_entry(entry)) {
3732 ret = VM_FAULT_HWPOISON;
3733 } else if (is_pte_marker_entry(entry)) {
3734 ret = handle_pte_marker(vmf);
3735 } else {
3736 print_bad_pte(vma, vmf->address, vmf->orig_pte, NULL);
3737 ret = VM_FAULT_SIGBUS;
3738 }
3739 goto out;
3740 }
3741
3742 /* Prevent swapoff from happening to us. */
3743 si = get_swap_device(entry);
3744 if (unlikely(!si))
3745 goto out;
3746
3747 folio = swap_cache_get_folio(entry, vma, vmf->address);
3748 if (folio)
3749 page = folio_file_page(folio, swp_offset(entry));
3750 swapcache = folio;
3751
3752 if (!folio) {
3753 if (data_race(si->flags & SWP_SYNCHRONOUS_IO) &&
3754 __swap_count(entry) == 1) {
3755 /* skip swapcache */
3756 folio = vma_alloc_folio(GFP_HIGHUSER_MOVABLE, 0,
3757 vma, vmf->address, false);
3758 page = &folio->page;
3759 if (folio) {
3760 __folio_set_locked(folio);
3761 __folio_set_swapbacked(folio);
3762
3763 if (mem_cgroup_swapin_charge_folio(folio,
3764 vma->vm_mm, GFP_KERNEL,
3765 entry)) {
3766 ret = VM_FAULT_OOM;
3767 goto out_page;
3768 }
3769 mem_cgroup_swapin_uncharge_swap(entry);
3770
3771 shadow = get_shadow_from_swap_cache(entry);
3772 if (shadow)
3773 workingset_refault(folio, shadow);
3774
3775 folio_add_lru(folio);
3776
3777 /* To provide entry to swap_readpage() */
3778 folio_set_swap_entry(folio, entry);
3779 swap_readpage(page, true, NULL);
3780 folio->private = NULL;
3781 }
3782 } else {
3783 page = swapin_readahead(entry, GFP_HIGHUSER_MOVABLE,
3784 vmf);
3785 if (page)
3786 folio = page_folio(page);
3787 swapcache = folio;
3788 }
3789
3790 if (!folio) {
3791 /*
3792 * Back out if somebody else faulted in this pte
3793 * while we released the pte lock.
3794 */
3795 vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd,
3796 vmf->address, &vmf->ptl);
3797 if (likely(pte_same(*vmf->pte, vmf->orig_pte)))
3798 ret = VM_FAULT_OOM;
3799 goto unlock;
3800 }
3801
3802 /* Had to read the page from swap area: Major fault */
3803 ret = VM_FAULT_MAJOR;
3804 count_vm_event(PGMAJFAULT);
3805 count_memcg_event_mm(vma->vm_mm, PGMAJFAULT);
3806 } else if (PageHWPoison(page)) {
3807 /*
3808 * hwpoisoned dirty swapcache pages are kept for killing
3809 * owner processes (which may be unknown at hwpoison time)
3810 */
3811 ret = VM_FAULT_HWPOISON;
3812 goto out_release;
3813 }
3814
3815 locked = folio_lock_or_retry(folio, vma->vm_mm, vmf->flags);
3816
3817 if (!locked) {
3818 ret |= VM_FAULT_RETRY;
3819 goto out_release;
3820 }
3821
3822 if (swapcache) {
3823 /*
3824 * Make sure folio_free_swap() or swapoff did not release the
3825 * swapcache from under us. The page pin, and pte_same test
3826 * below, are not enough to exclude that. Even if it is still
3827 * swapcache, we need to check that the page's swap has not
3828 * changed.
3829 */
3830 if (unlikely(!folio_test_swapcache(folio) ||
3831 page_private(page) != entry.val))
3832 goto out_page;
3833
3834 /*
3835 * KSM sometimes has to copy on read faults, for example, if
3836 * page->index of !PageKSM() pages would be nonlinear inside the
3837 * anon VMA -- PageKSM() is lost on actual swapout.
3838 */
3839 page = ksm_might_need_to_copy(page, vma, vmf->address);
3840 if (unlikely(!page)) {
3841 ret = VM_FAULT_OOM;
3842 goto out_page;
> 3843 } els if (unlikely(PTR_ERR(page) == -EHWPOISON)) {
3844 ret = VM_FAULT_HWPOISON;
3845 goto out_page;
3846 }
3847 folio = page_folio(page);
3848
3849 /*
3850 * If we want to map a page that's in the swapcache writable, we
3851 * have to detect via the refcount if we're really the exclusive
3852 * owner. Try removing the extra reference from the local LRU
3853 * pagevecs if required.
3854 */
3855 if ((vmf->flags & FAULT_FLAG_WRITE) && folio == swapcache &&
3856 !folio_test_ksm(folio) && !folio_test_lru(folio))
3857 lru_add_drain();
3858 }
3859
3860 cgroup_throttle_swaprate(page, GFP_KERNEL);
3861
3862 /*
3863 * Back out if somebody else already faulted in this pte.
3864 */
3865 vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, vmf->address,
3866 &vmf->ptl);
3867 if (unlikely(!pte_same(*vmf->pte, vmf->orig_pte)))
3868 goto out_nomap;
3869
3870 if (unlikely(!folio_test_uptodate(folio))) {
3871 ret = VM_FAULT_SIGBUS;
3872 goto out_nomap;
3873 }
3874
3875 /*
3876 * PG_anon_exclusive reuses PG_mappedtodisk for anon pages. A swap pte
3877 * must never point at an anonymous page in the swapcache that is
3878 * PG_anon_exclusive. Sanity check that this holds and especially, that
3879 * no filesystem set PG_mappedtodisk on a page in the swapcache. Sanity
3880 * check after taking the PT lock and making sure that nobody
3881 * concurrently faulted in this page and set PG_anon_exclusive.
3882 */
3883 BUG_ON(!folio_test_anon(folio) && folio_test_mappedtodisk(folio));
3884 BUG_ON(folio_test_anon(folio) && PageAnonExclusive(page));
3885
3886 /*
3887 * Check under PT lock (to protect against concurrent fork() sharing
3888 * the swap entry concurrently) for certainly exclusive pages.
3889 */
3890 if (!folio_test_ksm(folio)) {
3891 /*
3892 * Note that pte_swp_exclusive() == false for architectures
3893 * without __HAVE_ARCH_PTE_SWP_EXCLUSIVE.
3894 */
3895 exclusive = pte_swp_exclusive(vmf->orig_pte);
3896 if (folio != swapcache) {
3897 /*
3898 * We have a fresh page that is not exposed to the
3899 * swapcache -> certainly exclusive.
3900 */
3901 exclusive = true;
3902 } else if (exclusive && folio_test_writeback(folio) &&
3903 data_race(si->flags & SWP_STABLE_WRITES)) {
3904 /*
3905 * This is tricky: not all swap backends support
3906 * concurrent page modifications while under writeback.
3907 *
3908 * So if we stumble over such a page in the swapcache
3909 * we must not set the page exclusive, otherwise we can
3910 * map it writable without further checks and modify it
3911 * while still under writeback.
3912 *
3913 * For these problematic swap backends, simply drop the
3914 * exclusive marker: this is perfectly fine as we start
3915 * writeback only if we fully unmapped the page and
3916 * there are no unexpected references on the page after
3917 * unmapping succeeded. After fully unmapped, no
3918 * further GUP references (FOLL_GET and FOLL_PIN) can
3919 * appear, so dropping the exclusive marker and mapping
3920 * it only R/O is fine.
3921 */
3922 exclusive = false;
3923 }
3924 }
3925
3926 /*
3927 * Remove the swap entry and conditionally try to free up the swapcache.
3928 * We're already holding a reference on the page but haven't mapped it
3929 * yet.
3930 */
3931 swap_free(entry);
3932 if (should_try_to_free_swap(folio, vma, vmf->flags))
3933 folio_free_swap(folio);
3934
3935 inc_mm_counter(vma->vm_mm, MM_ANONPAGES);
3936 dec_mm_counter(vma->vm_mm, MM_SWAPENTS);
3937 pte = mk_pte(page, vma->vm_page_prot);
3938
3939 /*
3940 * Same logic as in do_wp_page(); however, optimize for pages that are
3941 * certainly not shared either because we just allocated them without
3942 * exposing them to the swapcache or because the swap entry indicates
3943 * exclusivity.
3944 */
3945 if (!folio_test_ksm(folio) &&
3946 (exclusive || folio_ref_count(folio) == 1)) {
3947 if (vmf->flags & FAULT_FLAG_WRITE) {
3948 pte = maybe_mkwrite(pte_mkdirty(pte), vma);
3949 vmf->flags &= ~FAULT_FLAG_WRITE;
3950 }
3951 rmap_flags |= RMAP_EXCLUSIVE;
3952 }
3953 flush_icache_page(vma, page);
3954 if (pte_swp_soft_dirty(vmf->orig_pte))
3955 pte = pte_mksoft_dirty(pte);
3956 if (pte_swp_uffd_wp(vmf->orig_pte)) {
3957 pte = pte_mkuffd_wp(pte);
3958 pte = pte_wrprotect(pte);
3959 }
3960 vmf->orig_pte = pte;
3961
3962 /* ksm created a completely new copy */
3963 if (unlikely(folio != swapcache && swapcache)) {
3964 page_add_new_anon_rmap(page, vma, vmf->address);
3965 folio_add_lru_vma(folio, vma);
3966 } else {
3967 page_add_anon_rmap(page, vma, vmf->address, rmap_flags);
3968 }
3969
3970 VM_BUG_ON(!folio_test_anon(folio) ||
3971 (pte_write(pte) && !PageAnonExclusive(page)));
3972 set_pte_at(vma->vm_mm, vmf->address, vmf->pte, pte);
3973 arch_do_swap_page(vma->vm_mm, vma, vmf->address, pte, vmf->orig_pte);
3974
3975 folio_unlock(folio);
3976 if (folio != swapcache && swapcache) {
3977 /*
3978 * Hold the lock to avoid the swap entry to be reused
3979 * until we take the PT lock for the pte_same() check
3980 * (to avoid false positives from pte_same). For
3981 * further safety release the lock after the swap_free
3982 * so that the swap count won't change under a
3983 * parallel locked swapcache.
3984 */
3985 folio_unlock(swapcache);
3986 folio_put(swapcache);
3987 }
3988
3989 if (vmf->flags & FAULT_FLAG_WRITE) {
3990 ret |= do_wp_page(vmf);
3991 if (ret & VM_FAULT_ERROR)
3992 ret &= VM_FAULT_ERROR;
3993 goto out;
3994 }
3995
3996 /* No need to invalidate - it was non-present before */
3997 update_mmu_cache(vma, vmf->address, vmf->pte);
3998 unlock:
3999 pte_unmap_unlock(vmf->pte, vmf->ptl);
4000 out:
4001 if (si)
4002 put_swap_device(si);
4003 return ret;
4004 out_nomap:
4005 pte_unmap_unlock(vmf->pte, vmf->ptl);
4006 out_page:
4007 folio_unlock(folio);
4008 out_release:
4009 folio_put(folio);
4010 if (folio != swapcache && swapcache) {
4011 folio_unlock(swapcache);
4012 folio_put(swapcache);
4013 }
4014 if (si)
4015 put_swap_device(si);
4016 return ret;
4017 }
4018
--
0-DAY CI Kernel Test Service
https://01.org/lkp
On Fri, 9 Dec 2022 15:28:01 +0800 Kefeng Wang <[email protected]> wrote:
> When the kernel copy a page from ksm_might_need_to_copy(), but runs
> into an uncorrectable error, it will crash since poisoned page is
> consumed by kernel, this is similar to Copy-on-write poison recovery,
> When an error is detected during the page copy, return VM_FAULT_HWPOISON,
> which help us to avoid system crash. Note, memory failure on a KSM
> page will be skipped, but still call memory_failure_queue() to be
> consistent with general memory failure process.
Thanks. Sorry, lots of paperwork and bureaucracy:
Is a copy of the oops(?) output available?
Did someone else report this? If so, is a Reported-by available for
that? And a Link: for the Reported-by:, which is a coming thing.
Can we identify a Fixes: target?
Is a cc:stable appropriate?
On 2022/12/10 8:50, Andrew Morton wrote:
> On Fri, 9 Dec 2022 15:28:01 +0800 Kefeng Wang <[email protected]> wrote:
>
>> When the kernel copy a page from ksm_might_need_to_copy(), but runs
>> into an uncorrectable error, it will crash since poisoned page is
>> consumed by kernel, this is similar to Copy-on-write poison recovery,
>> When an error is detected during the page copy, return VM_FAULT_HWPOISON,
>> which help us to avoid system crash. Note, memory failure on a KSM
>> page will be skipped, but still call memory_failure_queue() to be
>> consistent with general memory failure process.
> Thanks. Sorry, lots of paperwork and bureaucracy:
>
>
> Is a copy of the oops(?) output available?
>
> Did someone else report this? If so, is a Reported-by available for
> that? And a Link: for the Reported-by:, which is a coming thing.
>
> Can we identify a Fixes: target?
>
> Is a cc:stable appropriate?
We are trying to support ARCH_HAS_COPY_MC on arm64[1] and trying to
recover from CoW faults[2],
also tony do the same thing(recover from CoW) on X86[3]. The kernel copy
in ksm_might_need_to_copy()
could recover, this is an enhance of COPY_MC, so I think no need to add
Fixes and stable.
Thanks.
[1]
https://lore.kernel.org/linux-arm-kernel/[email protected]/
[2]
https://lore.kernel.org/linux-arm-kernel/[email protected]/
[3]
https://lore.kernel.org/lkml/[email protected]/
>
On 2022/12/9 15:28, Kefeng Wang wrote:
> When the kernel copy a page from ksm_might_need_to_copy(), but runs
> into an uncorrectable error, it will crash since poisoned page is
> consumed by kernel, this is similar to Copy-on-write poison recovery,
> When an error is detected during the page copy, return VM_FAULT_HWPOISON,
> which help us to avoid system crash. Note, memory failure on a KSM
> page will be skipped, but still call memory_failure_queue() to be
> consistent with general memory failure process.
Thanks for your patch.
>
> Signed-off-by: Kefeng Wang <[email protected]>
> ---
> v2: fix type error
>
> mm/ksm.c | 8 ++++++--
> mm/memory.c | 3 +++
> mm/swapfile.c | 2 +-
> 3 files changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/mm/ksm.c b/mm/ksm.c
> index dd02780c387f..83e2f74ae7da 100644
> --- a/mm/ksm.c
> +++ b/mm/ksm.c
> @@ -2629,8 +2629,12 @@ struct page *ksm_might_need_to_copy(struct page *page,
> new_page = NULL;
> }
> if (new_page) {
> - copy_user_highpage(new_page, page, address, vma);
> -
> + if (copy_mc_user_highpage(new_page, page, address, vma)) {
> + put_page(new_page);
> + new_page = ERR_PTR(-EHWPOISON);
> + memory_failure_queue(page_to_pfn(page), 0);
> + return new_page;
> + }
> SetPageDirty(new_page);
> __SetPageUptodate(new_page);
> __SetPageLocked(new_page);
> diff --git a/mm/memory.c b/mm/memory.c
> index aad226daf41b..5b2c137dfb2a 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -3840,6 +3840,9 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
> if (unlikely(!page)) {
> ret = VM_FAULT_OOM;
> goto out_page;
> + } else if (unlikely(PTR_ERR(page) == -EHWPOISON)) {
> + ret = VM_FAULT_HWPOISON;
> + goto out_page;
> }
> folio = page_folio(page);
>
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index 908a529bca12..d479811bc311 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -1767,7 +1767,7 @@ static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
>
> swapcache = page;
> page = ksm_might_need_to_copy(page, vma, addr);
> - if (unlikely(!page))
> + if (IS_ERR_OR_NULL(page))
IMHO, it might be better to install a hwpoison entry here. Or later swapoff ops will trigger
the uncorrectable error again?
Thanks,
Miaohe Lin
On 2022/12/12 10:36, Miaohe Lin wrote:
> On 2022/12/9 15:28, Kefeng Wang wrote:
>> When the kernel copy a page from ksm_might_need_to_copy(), but runs
>> into an uncorrectable error, it will crash since poisoned page is
>> consumed by kernel, this is similar to Copy-on-write poison recovery,
>> When an error is detected during the page copy, return VM_FAULT_HWPOISON,
>> which help us to avoid system crash. Note, memory failure on a KSM
>> page will be skipped, but still call memory_failure_queue() to be
>> consistent with general memory failure process.
...
>
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index 908a529bca12..d479811bc311 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -1767,7 +1767,7 @@ static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
>
> swapcache = page;
> page = ksm_might_need_to_copy(page, vma, addr);
> - if (unlikely(!page))
> + if (IS_ERR_OR_NULL(page))
> IMHO, it might be better to install a hwpoison entry here. Or later swapoff ops will trigger
> the uncorrectable error again?
Thanks for you suggestion, will do in v3.
> Thanks,
> Miaohe Lin
>