Re: [PATCH v2 18/35] mm: implement speculative handling in do_anonymous_page()
From: kernel test robot
Date: Fri Jan 28 2022 - 16:04:25 EST
Hi Michel,
Thank you for the patch! Perhaps something to improve:
[auto build test WARNING on linus/master]
[also build test WARNING on v5.17-rc1 next-20220128]
[cannot apply to tip/x86/mm arm64/for-next/core powerpc/next hnaz-mm/master]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]
url: https://github.com/0day-ci/linux/commits/Michel-Lespinasse/Speculative-page-faults/20220128-212122
base: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 145d9b498fc827b79c1260b4caa29a8e59d4c2b9
config: arm-vt8500_v6_v7_defconfig (https://download.01.org/0day-ci/archive/20220129/202201290445.uKuWeLmf-lkp@xxxxxxxxx/config)
compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project 33b45ee44b1f32ffdbc995e6fec806271b4b3ba4)
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
# install arm cross compiling tool for clang build
# apt-get install binutils-arm-linux-gnueabi
# https://github.com/0day-ci/linux/commit/fa5331bae2e49ce86eff959390b451b7401f9156
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Michel-Lespinasse/Speculative-page-faults/20220128-212122
git checkout fa5331bae2e49ce86eff959390b451b7401f9156
# save the config file to linux build tree
mkdir build_dir
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=arm SHELL=/bin/bash
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@xxxxxxxxx>
All warnings (new ones prefixed by >>):
>> mm/memory.c:3876:20: warning: variable 'vmf' is uninitialized when used within its own initialization [-Wuninitialized]
if (!pte_map_lock(vmf)) {
~~~~~~~~~~~~~^~~~
include/linux/mm.h:3418:25: note: expanded from macro 'pte_map_lock'
struct vm_fault *vmf = __vmf; \
~~~ ^~~~~
1 warning generated.
vim +/vmf +3876 mm/memory.c
3808
3809 /*
3810 * We enter with non-exclusive mmap_lock (to exclude vma changes,
3811 * but allow concurrent faults), and pte mapped but not yet locked.
3812 * We return with mmap_lock still held, but pte unmapped and unlocked.
3813 */
3814 static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
3815 {
3816 struct vm_area_struct *vma = vmf->vma;
3817 struct page *page = NULL;
3818 vm_fault_t ret = 0;
3819 pte_t entry;
3820
3821 /* File mapping without ->vm_ops ? */
3822 if (vma->vm_flags & VM_SHARED)
3823 return VM_FAULT_SIGBUS;
3824
3825 /*
3826 * Use pte_alloc() instead of pte_alloc_map(). We can't run
3827 * pte_offset_map() on pmds where a huge pmd might be created
3828 * from a different thread.
3829 *
3830 * pte_alloc_map() is safe to use under mmap_write_lock(mm) or when
3831 * parallel threads are excluded by other means.
3832 *
3833 * Here we only have mmap_read_lock(mm).
3834 */
3835 if (pte_alloc(vma->vm_mm, vmf->pmd))
3836 return VM_FAULT_OOM;
3837
3838 /* See comment in __handle_mm_fault() */
3839 if (unlikely(pmd_trans_unstable(vmf->pmd)))
3840 return 0;
3841
3842 /* Use the zero-page for reads */
3843 if (!(vmf->flags & FAULT_FLAG_WRITE) &&
3844 !mm_forbids_zeropage(vma->vm_mm)) {
3845 entry = pte_mkspecial(pfn_pte(my_zero_pfn(vmf->address),
3846 vma->vm_page_prot));
3847 } else {
3848 /* Allocate our own private page. */
3849 if (unlikely(!vma->anon_vma)) {
3850 if (vmf->flags & FAULT_FLAG_SPECULATIVE)
3851 return VM_FAULT_RETRY;
3852 if (__anon_vma_prepare(vma))
3853 goto oom;
3854 }
3855 page = alloc_zeroed_user_highpage_movable(vma, vmf->address);
3856 if (!page)
3857 goto oom;
3858
3859 if (mem_cgroup_charge(page_folio(page), vma->vm_mm, GFP_KERNEL))
3860 goto oom_free_page;
3861 cgroup_throttle_swaprate(page, GFP_KERNEL);
3862
3863 /*
3864 * The memory barrier inside __SetPageUptodate makes sure that
3865 * preceding stores to the page contents become visible before
3866 * the set_pte_at() write.
3867 */
3868 __SetPageUptodate(page);
3869
3870 entry = mk_pte(page, vma->vm_page_prot);
3871 entry = pte_sw_mkyoung(entry);
3872 if (vma->vm_flags & VM_WRITE)
3873 entry = pte_mkwrite(pte_mkdirty(entry));
3874 }
3875
> 3876 if (!pte_map_lock(vmf)) {
3877 ret = VM_FAULT_RETRY;
3878 goto release;
3879 }
3880 if (!pte_none(*vmf->pte)) {
3881 update_mmu_tlb(vma, vmf->address, vmf->pte);
3882 goto unlock;
3883 }
3884
3885 ret = check_stable_address_space(vma->vm_mm);
3886 if (ret)
3887 goto unlock;
3888
3889 /* Deliver the page fault to userland, check inside PT lock */
3890 if (userfaultfd_missing(vma)) {
3891 pte_unmap_unlock(vmf->pte, vmf->ptl);
3892 if (page)
3893 put_page(page);
3894 if (vmf->flags & FAULT_FLAG_SPECULATIVE)
3895 return VM_FAULT_RETRY;
3896 return handle_userfault(vmf, VM_UFFD_MISSING);
3897 }
3898
3899 if (page) {
3900 inc_mm_counter_fast(vma->vm_mm, MM_ANONPAGES);
3901 page_add_new_anon_rmap(page, vma, vmf->address, false);
3902 lru_cache_add_inactive_or_unevictable(page, vma);
3903 }
3904
3905 set_pte_at(vma->vm_mm, vmf->address, vmf->pte, entry);
3906
3907 /* No need to invalidate - it was non-present before */
3908 update_mmu_cache(vma, vmf->address, vmf->pte);
3909 pte_unmap_unlock(vmf->pte, vmf->ptl);
3910 return 0;
3911 unlock:
3912 pte_unmap_unlock(vmf->pte, vmf->ptl);
3913 release:
3914 if (page)
3915 put_page(page);
3916 return ret;
3917 oom_free_page:
3918 put_page(page);
3919 oom:
3920 return VM_FAULT_OOM;
3921 }
3922
---
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