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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 76980C0021 X-Stat-Signature: u988nwawmc1r9yk3xxcn9p1j7icfhuak X-HE-Tag: 1700158429-910650 X-HE-Meta: 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 cWQZ+AlH 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 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: List-Subscribe: List-Unsubscribe: > It should be fine, as: > > static void make_uffd_wp_pte(struct vm_area_struct *vma, > unsigned long addr, pte_t *pte) > { > pte_t ptent = ptep_get(pte); > > #ifndef CONFIG_USERFAULTFD_ > > if (pte_present(ptent)) { > pte_t old_pte; > > old_pte = ptep_modify_prot_start(vma, addr, pte); > ptent = pte_mkuffd_wp(ptent); > ptep_modify_prot_commit(vma, addr, pte, old_pte, ptent); > } else if (is_swap_pte(ptent)) { > ptent = pte_swp_mkuffd_wp(ptent); > set_pte_at(vma->vm_mm, addr, pte, ptent); > } else { <----------------- this must be pte_none() already > set_pte_at(vma->vm_mm, addr, pte, > make_pte_marker(PTE_MARKER_UFFD_WP)); > } > } Indeed! Is pte_swp_mkuffd_wp() reasonable for pte markers? I rememebr that we don't support multiple markers yet, so it might be good enough. > >> >> 2) We get the error on arm64, which does *not* support uffd-wp. Do we >> maybe end up calling make_uffd_wp_pte() and place a pte marker, even >> though we don't have CONFIG_PTE_MARKER_UFFD_WP? >> >> >> static inline bool pte_marker_entry_uffd_wp(swp_entry_t entry) >> { >> #ifdef CONFIG_PTE_MARKER_UFFD_WP >> return is_pte_marker_entry(entry) && >> (pte_marker_get(entry) & PTE_MARKER_UFFD_WP); >> #else >> return false; >> #endif >> } >> >> Will always return false without CONFIG_PTE_MARKER_UFFD_WP. >> >> But make_uffd_wp_pte() might just happily place an entry. Hm. >> >> >> The following might fix the problem: >> [...] > > I'd like to double check with Muhammad (as I didn't actually follow his > work in the latest versions.. quite a lot changed), but I _think_ > fundamentally we missed something important in the fast path, and I think > it applies even to archs that support uffd.. > > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c > index e91085d79926..3b81baabd22a 100644 > --- a/fs/proc/task_mmu.c > +++ b/fs/proc/task_mmu.c > @@ -2171,7 +2171,8 @@ static int pagemap_scan_pmd_entry(pmd_t *pmd, unsigned long start, > return 0; > } > > - if (!p->vec_out) { > + if (!p->vec_out && > + (p->arg.flags & PM_SCAN_WP_MATCHING)) Ouch, yes. So that's the global fence I was wondering where to find it. -- Cheers, David / dhildenb