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Shutemov" , Andrea Arcangeli Subject: [PATCH v7 02/23] mm: Teach core mm about pte markers Date: Fri, 4 Mar 2022 13:16:47 +0800 Message-Id: <20220304051708.86193-3-peterx@redhat.com> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20220304051708.86193-1-peterx@redhat.com> References: <20220304051708.86193-1-peterx@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This patch still does not use pte marker in any way, however it teaches the core mm about the pte marker idea. For example, handle_pte_marker() is introduced that will parse and handle all the pte marker faults. Many of the places are more about commenting it up - so that we know there's the possibility of pte marker showing up, and why we don't need special code for the cases. Signed-off-by: Peter Xu --- fs/userfaultfd.c | 10 ++++++---- mm/filemap.c | 5 +++++ mm/hmm.c | 2 +- mm/memcontrol.c | 8 ++++++-- mm/memory.c | 23 +++++++++++++++++++++++ mm/mincore.c | 3 ++- mm/mprotect.c | 3 +++ 7 files changed, 46 insertions(+), 8 deletions(-) diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index aa0c47cb0d16..8b4a94f5a238 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -249,9 +249,10 @@ static inline bool userfaultfd_huge_must_wait(struct userfaultfd_ctx *ctx, /* * Lockless access: we're in a wait_event so it's ok if it - * changes under us. + * changes under us. PTE markers should be handled the same as none + * ptes here. */ - if (huge_pte_none(pte)) + if (huge_pte_none_mostly(pte)) ret = true; if (!huge_pte_write(pte) && (reason & VM_UFFD_WP)) ret = true; @@ -330,9 +331,10 @@ static inline bool userfaultfd_must_wait(struct userfaultfd_ctx *ctx, pte = pte_offset_map(pmd, address); /* * Lockless access: we're in a wait_event so it's ok if it - * changes under us. + * changes under us. PTE markers should be handled the same as none + * ptes here. */ - if (pte_none(*pte)) + if (pte_none_mostly(*pte)) ret = true; if (!pte_write(*pte) && (reason & VM_UFFD_WP)) ret = true; diff --git a/mm/filemap.c b/mm/filemap.c index 8f7e6088ee2a..464b8f0f111a 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -3379,6 +3379,11 @@ vm_fault_t filemap_map_pages(struct vm_fault *vmf, vmf->pte += xas.xa_index - last_pgoff; last_pgoff = xas.xa_index; + /* + * NOTE: If there're PTE markers, we'll leave them to be + * handled in the specific fault path, and it'll prohibit the + * fault-around logic. + */ if (!pte_none(*vmf->pte)) goto unlock; diff --git a/mm/hmm.c b/mm/hmm.c index af71aac3140e..3fd3242c5e50 100644 --- a/mm/hmm.c +++ b/mm/hmm.c @@ -239,7 +239,7 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr, pte_t pte = *ptep; uint64_t pfn_req_flags = *hmm_pfn; - if (pte_none(pte)) { + if (pte_none_mostly(pte)) { required_fault = hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, 0); if (required_fault) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index f79bb3f25ce4..bba3b7e9f699 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -5636,10 +5636,14 @@ static enum mc_target_type get_mctgt_type(struct vm_area_struct *vma, if (pte_present(ptent)) page = mc_handle_present_pte(vma, addr, ptent); + else if (pte_none_mostly(ptent)) + /* + * PTE markers should be treated as a none pte here, separated + * from other swap handling below. + */ + page = mc_handle_file_pte(vma, addr, ptent); else if (is_swap_pte(ptent)) page = mc_handle_swap_pte(vma, ptent, &ent); - else if (pte_none(ptent)) - page = mc_handle_file_pte(vma, addr, ptent); if (!page && !ent.val) return ret; diff --git a/mm/memory.c b/mm/memory.c index a0ca84756159..22d24ea7b87d 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -99,6 +99,8 @@ struct page *mem_map; EXPORT_SYMBOL(mem_map); #endif +static vm_fault_t do_fault(struct vm_fault *vmf); + /* * A number of key systems in x86 including ioremap() rely on the assumption * that high_memory defines the upper bound on direct map memory, then end @@ -1419,6 +1421,8 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb, if (!should_zap_page(details, page)) continue; rss[mm_counter(page)]--; + } else if (is_pte_marker_entry(entry)) { + /* By default, simply drop all pte markers when zap */ } else if (is_hwpoison_entry(entry)) { if (!should_zap_cows(details)) continue; @@ -3508,6 +3512,23 @@ static inline bool should_try_to_free_swap(struct page *page, page_count(page) == 2; } +static vm_fault_t handle_pte_marker(struct vm_fault *vmf) +{ + swp_entry_t entry = pte_to_swp_entry(vmf->orig_pte); + unsigned long marker = pte_marker_get(entry); + + /* + * PTE markers should always be with file-backed memories, and the + * marker should never be empty. If anything weird happened, the best + * thing to do is to kill the process along with its mm. + */ + if (WARN_ON_ONCE(vma_is_anonymous(vmf->vma) || !marker)) + return VM_FAULT_SIGBUS; + + /* TODO: handle pte markers */ + return 0; +} + /* * We enter with non-exclusive mmap_lock (to exclude vma changes, * but allow concurrent faults), and pte mapped but not yet locked. @@ -3544,6 +3565,8 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) ret = vmf->page->pgmap->ops->migrate_to_ram(vmf); } else if (is_hwpoison_entry(entry)) { ret = VM_FAULT_HWPOISON; + } else if (is_pte_marker_entry(entry)) { + ret = handle_pte_marker(vmf); } else { print_bad_pte(vma, vmf->address, vmf->orig_pte, NULL); ret = VM_FAULT_SIGBUS; diff --git a/mm/mincore.c b/mm/mincore.c index 9122676b54d6..736869f4b409 100644 --- a/mm/mincore.c +++ b/mm/mincore.c @@ -121,7 +121,8 @@ static int mincore_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, for (; addr != end; ptep++, addr += PAGE_SIZE) { pte_t pte = *ptep; - if (pte_none(pte)) + /* We need to do cache lookup too for pte markers */ + if (pte_none_mostly(pte)) __mincore_unmapped_range(addr, addr + PAGE_SIZE, vma, vec); else if (pte_present(pte)) diff --git a/mm/mprotect.c b/mm/mprotect.c index b69ce7a7b2b7..6d179c720089 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -184,6 +184,9 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd, newpte = pte_swp_mksoft_dirty(newpte); if (pte_swp_uffd_wp(oldpte)) newpte = pte_swp_mkuffd_wp(newpte); + } else if (is_pte_marker_entry(entry)) { + /* Skip it, the same as none pte */ + continue; } else { newpte = oldpte; } -- 2.32.0