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Fri, 24 Mar 2023 15:32:06 -0700 (PDT) MIME-Version: 1.0 References: <20230305065112.1932255-1-jiaqiyan@google.com> <20230305065112.1932255-2-jiaqiyan@google.com> In-Reply-To: From: Jiaqi Yan Date: Fri, 24 Mar 2023 15:31:55 -0700 Message-ID: Subject: Re: [PATCH v10 1/3] mm/khugepaged: recover from poisoned anonymous memory To: Yang Shi Cc: kirill.shutemov@linux.intel.com, kirill@shutemov.name, tongtiangen@huawei.com, tony.luck@intel.com, akpm@linux-foundation.org, naoya.horiguchi@nec.com, linmiaohe@huawei.com, linux-mm@kvack.org, osalvador@suse.de, wangkefeng.wang@huawei.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: ud676pzhfg84e3hu54tj4tgr3prqfiik X-Rspam-User: X-Rspamd-Queue-Id: A2D0580011 X-Rspamd-Server: rspam06 X-HE-Tag: 1679697127-362272 X-HE-Meta: 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 G6g+iFML 93I0mpxqudbLtk/BLvtxMW7/I7HAo1REMmfGUaiQDdHGLIslMobgJlUrZE/Sq3s9f1kymKKQZKk6pNHGOIDUhsVNd4GhdiIMEAE7HTAdDKbYZm3wB0euntOJ+ZXryQ7Y0Wieiu7520NCZRLaWRiKQKNV8p0SC++9i+9Sn/jDrDeG+2pZX04I0lFdph/p0Ch/gOdaBzGCB+YxSw32+m4N+kSnTbSDM2VbglUSFLCmWGU4/g8rhgxjt5pVCtFrrwrS4mjxD4wLTqzgTIl80UNlg1/Uf3fzrlUu6PuvdwA0T1CO5hyg= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Mar 24, 2023 at 1:11=E2=80=AFPM Yang Shi wrot= e: > > On Fri, Mar 24, 2023 at 8:34=E2=80=AFAM Jiaqi Yan w= rote: > > > > On Thu, Mar 23, 2023 at 2:38=E2=80=AFPM Yang Shi = wrote: > > > > > > On Sat, Mar 4, 2023 at 10:51=E2=80=AFPM Jiaqi Yan wrote: > > > > > > > > Make __collapse_huge_page_copy return whether copying anonymous pag= es > > > > succeeded, and make collapse_huge_page handle the return status. > > > > > > > > Break existing PTE scan loop into two for-loops. The first loop cop= ies > > > > source pages into target huge page, and can fail gracefully when ru= nning > > > > into memory errors in source pages. If copying all pages succeeds, = the > > > > second loop releases and clears up these normal pages. Otherwise, t= he > > > > second loop rolls back the page table and page states by: > > > > - re-establishing the original PTEs-to-PMD connection. > > > > - releasing source pages back to their LRU list. > > > > > > > > Tested manually: > > > > 0. Enable khugepaged on system under test. > > > > 1. Start a two-thread application. Each thread allocates a chunk of > > > > non-huge anonymous memory buffer. > > > > 2. Pick 4 random buffer locations (2 in each thread) and inject > > > > uncorrectable memory errors at corresponding physical addresses. > > > > 3. Signal both threads to make their memory buffer collapsible, i.e= . > > > > calling madvise(MADV_HUGEPAGE). > > > > 4. Wait and check kernel log: khugepaged is able to recover from po= isoned > > > > pages and skips collapsing them. > > > > 5. Signal both threads to inspect their buffer contents and make su= re no > > > > data corruption. > > > > > > > > Signed-off-by: Jiaqi Yan > > > > --- > > > > include/trace/events/huge_memory.h | 3 +- > > > > mm/khugepaged.c | 148 ++++++++++++++++++++++++-= ---- > > > > 2 files changed, 128 insertions(+), 23 deletions(-) > > > > > > > > diff --git a/include/trace/events/huge_memory.h b/include/trace/eve= nts/huge_memory.h > > > > index 3e6fb05852f9a..46cce509957ba 100644 > > > > --- a/include/trace/events/huge_memory.h > > > > +++ b/include/trace/events/huge_memory.h > > > > @@ -36,7 +36,8 @@ > > > > EM( SCAN_ALLOC_HUGE_PAGE_FAIL, "alloc_huge_page_failed") = \ > > > > EM( SCAN_CGROUP_CHARGE_FAIL, "ccgroup_charge_failed") = \ > > > > EM( SCAN_TRUNCATED, "truncated") = \ > > > > - EMe(SCAN_PAGE_HAS_PRIVATE, "page_has_private") = \ > > > > + EM( SCAN_PAGE_HAS_PRIVATE, "page_has_private") = \ > > > > + EMe(SCAN_COPY_MC, "copy_poisoned_page") = \ > > > > > > > > #undef EM > > > > #undef EMe > > > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > > > > index 27956d4404134..c3c217f6ebc6e 100644 > > > > --- a/mm/khugepaged.c > > > > +++ b/mm/khugepaged.c > > > > @@ -19,6 +19,7 @@ > > > > #include > > > > #include > > > > #include > > > > +#include > > > > > > > > #include > > > > #include > > > > @@ -55,6 +56,7 @@ enum scan_result { > > > > SCAN_CGROUP_CHARGE_FAIL, > > > > SCAN_TRUNCATED, > > > > SCAN_PAGE_HAS_PRIVATE, > > > > + SCAN_COPY_MC, > > > > }; > > > > > > > > #define CREATE_TRACE_POINTS > > > > @@ -681,47 +683,47 @@ static int __collapse_huge_page_isolate(struc= t vm_area_struct *vma, > > > > return result; > > > > } > > > > > > > > -static void __collapse_huge_page_copy(pte_t *pte, struct page *pag= e, > > > > - struct vm_area_struct *vma, > > > > - unsigned long address, > > > > - spinlock_t *ptl, > > > > - struct list_head *compound_pa= gelist) > > > > +static void __collapse_huge_page_copy_succeeded(pte_t *pte, > > > > + pmd_t *pmd, > > > > + struct vm_area_stru= ct *vma, > > > > + unsigned long addre= ss, > > > > + spinlock_t *pte_ptl= , > > > > + struct list_head *c= ompound_pagelist) > > > > { > > > > struct page *src_page, *tmp; > > > > pte_t *_pte; > > > > - for (_pte =3D pte; _pte < pte + HPAGE_PMD_NR; > > > > - _pte++, page++, address +=3D PAGE_S= IZE) { > > > > - pte_t pteval =3D *_pte; > > > > + pte_t pteval; > > > > + unsigned long _address; > > > > > > > > + for (_pte =3D pte, _address =3D address; _pte < pte + HPAGE= _PMD_NR; > > > > + _pte++, _address +=3D PAGE_SIZE) { > > > > + pteval =3D *_pte; > > > > if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval)= )) { > > > > - clear_user_highpage(page, address); > > > > add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1)= ; > > > > if (is_zero_pfn(pte_pfn(pteval))) { > > > > /* > > > > - * ptl mostly unnecessary. > > > > + * pte_ptl mostly unnecessary. > > > > */ > > > > - spin_lock(ptl); > > > > - ptep_clear(vma->vm_mm, address, _pt= e); > > > > - spin_unlock(ptl); > > > > + spin_lock(pte_ptl); > > > > > > Why did you have to rename ptl to pte_ptl? It seems unnecessary. > > > > Thanks, I will use `ptl` in the next version. > > > > > > > > > + pte_clear(vma->vm_mm, _address, _pt= e); > > > > + spin_unlock(pte_ptl); > > > > } > > > > } else { > > > > src_page =3D pte_page(pteval); > > > > - copy_user_highpage(page, src_page, address,= vma); > > > > if (!PageCompound(src_page)) > > > > release_pte_page(src_page); > > > > /* > > > > - * ptl mostly unnecessary, but preempt has = to > > > > - * be disabled to update the per-cpu stats > > > > + * pte_ptl mostly unnecessary, but preempt = has > > > > + * to be disabled to update the per-cpu sta= ts > > > > * inside page_remove_rmap(). > > > > */ > > > > - spin_lock(ptl); > > > > - ptep_clear(vma->vm_mm, address, _pte); > > > > + spin_lock(pte_ptl); > > > > + ptep_clear(vma->vm_mm, _address, _pte); > > > > page_remove_rmap(src_page, vma, false); > > > > - spin_unlock(ptl); > > > > + spin_unlock(pte_ptl); > > > > free_page_and_swap_cache(src_page); > > > > } > > > > } > > > > - > > > > list_for_each_entry_safe(src_page, tmp, compound_pagelist, = lru) { > > > > list_del(&src_page->lru); > > > > mod_node_page_state(page_pgdat(src_page), > > > > @@ -733,6 +735,104 @@ static void __collapse_huge_page_copy(pte_t *= pte, struct page *page, > > > > } > > > > } > > > > > > > > +static void __collapse_huge_page_copy_failed(pte_t *pte, > > > > + pmd_t *pmd, > > > > + pmd_t orig_pmd, > > > > + struct vm_area_struct = *vma, > > > > + unsigned long address, > > > > + struct list_head *comp= ound_pagelist) > > > > +{ > > > > + struct page *src_page, *tmp; > > > > + pte_t *_pte; > > > > + pte_t pteval; > > > > + unsigned long _address; > > > > + spinlock_t *pmd_ptl; > > > > + > > > > + /* > > > > + * Re-establish the PMD to point to the original page table > > > > + * entry. Restoring PMD needs to be done prior to releasing > > > > + * pages. Since pages are still isolated and locked here, > > > > + * acquiring anon_vma_lock_write is unnecessary. > > > > + */ > > > > + pmd_ptl =3D pmd_lock(vma->vm_mm, pmd); > > > > + pmd_populate(vma->vm_mm, pmd, pmd_pgtable(orig_pmd)); > > > > + spin_unlock(pmd_ptl); > > > > + /* > > > > + * Release both raw and compound pages isolated > > > > + * in __collapse_huge_page_isolate. > > > > + */ > > > > > > It looks like the below code could be replaced by release_pte_pages() > > > with advancing _pte to (pte + HPAGE_PMD_NR - 1). > > > > > > > Yeah, but I think _pte should be (pte + HPAGE_PMR_NR) because _pte is > > decremented before comparison in release_pte_pages(pte, _pte, > > compound_pagelist): > > > > while (--_pte >=3D pte) {...} > > > > Advancing _pte to (pte + HPAGE_PMD_NR - 1) may leave the last page not = released. > > Yeah, good catch. I think it is because the only user of > release_pte_pages() is __collapse_huge_page_isolate(). Once the loop > in it is done _pte is pte + HPAGE_PMD_NR. > Thanks for confirming ;) Since you have reviewed other 2 commits, I will soon send out V11 for your comments on this commit. > > > > > > > > > + for (_pte =3D pte, _address =3D address; _pte < pte + HPAGE= _PMD_NR; > > > > + _pte++, _address +=3D PAGE_SIZE) { > > > > + pteval =3D *_pte; > > > > + if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval)= )) > > > > + continue; > > > > + src_page =3D pte_page(pteval); > > > > + if (!PageCompound(src_page)) > > > > + release_pte_page(src_page); > > > > + } > > > > + list_for_each_entry_safe(src_page, tmp, compound_pagelist, = lru) { > > > > + list_del(&src_page->lru); > > > > + release_pte_page(src_page); > > > > + } > > > > +} > > > > + > > > > +/* > > > > + * __collapse_huge_page_copy - attempts to copy memory contents fr= om raw > > > > + * pages to a hugepage. Cleans up the raw pages if copying succeed= s; > > > > + * otherwise restores the original page table and releases isolate= d raw pages. > > > > + * Returns SCAN_SUCCEED if copying succeeds, otherwise returns SCA= N_COPY_MC. > > > > + * > > > > + * @pte: starting of the PTEs to copy from > > > > + * @page: the new hugepage to copy contents to > > > > + * @pmd: pointer to the new hugepage's PMD > > > > + * @orig_pmd: the original raw pages' PMD > > > > + * @vma: the original raw pages' virtual memory area > > > > + * @address: starting address to copy > > > > + * @pte_ptl: lock on raw pages' PTEs > > > > + * @compound_pagelist: list that stores compound pages > > > > + */ > > > > +static int __collapse_huge_page_copy(pte_t *pte, > > > > + struct page *page, > > > > + pmd_t *pmd, > > > > + pmd_t orig_pmd, > > > > + struct vm_area_struct *vma, > > > > + unsigned long address, > > > > + spinlock_t *pte_ptl, > > > > + struct list_head *compound_pag= elist) > > > > +{ > > > > + struct page *src_page; > > > > + pte_t *_pte; > > > > + pte_t pteval; > > > > + unsigned long _address; > > > > + int result =3D SCAN_SUCCEED; > > > > + > > > > + /* > > > > + * Copying pages' contents is subject to memory poison at a= ny iteration. > > > > + */ > > > > + for (_pte =3D pte, _address =3D address; _pte < pte + HPAGE= _PMD_NR; > > > > + _pte++, page++, _address +=3D PAGE_SIZE) { > > > > + pteval =3D *_pte; > > > > + if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval)= )) { > > > > + clear_user_highpage(page, _address); > > > > + continue; > > > > + } > > > > + src_page =3D pte_page(pteval); > > > > + if (copy_mc_user_highpage(page, src_page, _address,= vma) > 0) { > > > > + result =3D SCAN_COPY_MC; > > > > + break; > > > > + } > > > > + } > > > > + > > > > + if (likely(result =3D=3D SCAN_SUCCEED)) > > > > + __collapse_huge_page_copy_succeeded(pte, pmd, vma, = address, > > > > + pte_ptl, compou= nd_pagelist); > > > > + else > > > > + __collapse_huge_page_copy_failed(pte, pmd, orig_pmd= , vma, > > > > + address, compound_= pagelist); > > > > + > > > > + return result; > > > > +} > > > > + > > > > static void khugepaged_alloc_sleep(void) > > > > { > > > > DEFINE_WAIT(wait); > > > > @@ -1106,9 +1206,13 @@ static int collapse_huge_page(struct mm_stru= ct *mm, unsigned long address, > > > > */ > > > > anon_vma_unlock_write(vma->anon_vma); > > > > > > > > - __collapse_huge_page_copy(pte, hpage, vma, address, pte_ptl= , > > > > - &compound_pagelist); > > > > + result =3D __collapse_huge_page_copy(pte, hpage, pmd, _pmd, > > > > + vma, address, pte_ptl, > > > > + &compound_pagelist); > > > > pte_unmap(pte); > > > > + if (unlikely(result !=3D SCAN_SUCCEED)) > > > > + goto out_up_write; > > > > + > > > > /* > > > > * spin_lock() below is not the equivalent of smp_wmb(), bu= t > > > > * the smp_wmb() inside __SetPageUptodate() can be reused t= o > > > > -- > > > > 2.40.0.rc0.216.gc4246ad0f0-goog > > > >