From 57f3bb2b129e8cca7bb3e1cfe6c2d9b80c9d07f5 Mon Sep 17 00:00:00 2001 From: Michel Lespinasse Date: Mon, 24 Jan 2022 17:43:54 -0800 Subject: [PATCH] BACKPORT: FROMLIST: do_anonymous_page: reduce code duplication In do_anonymous_page(), we have separate cases for the zero page vs allocating new anonymous pages. However, once the pte entry has been computed, the rest of the handling (mapping and locking the page table, checking that we didn't lose a race with another page fault handler, etc) is identical between the two cases. This change reduces the code duplication between the two cases. Signed-off-by: Michel Lespinasse Conflicts: mm/memory.c 1. Trivial merge conflict caused by folios in mem_cgroup_charge call. Link: https://lore.kernel.org/all/20220128131006.67712-6-michel@lespinasse.org/ Bug: 161210518 Signed-off-by: Suren Baghdasaryan Change-Id: Ic19579571925878d632e43aa40b9f50cdf473ee6 --- mm/memory.c | 87 +++++++++++++++++++++++------------------------------ 1 file changed, 38 insertions(+), 49 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index 4adba986febd..0ed79b4aa49c 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3719,7 +3719,7 @@ out_release: static vm_fault_t do_anonymous_page(struct vm_fault *vmf) { struct vm_area_struct *vma = vmf->vma; - struct page *page; + struct page *page = NULL; vm_fault_t ret = 0; pte_t entry; @@ -3749,78 +3749,67 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf) !mm_forbids_zeropage(vma->vm_mm)) { entry = pte_mkspecial(pfn_pte(my_zero_pfn(vmf->address), vma->vm_page_prot)); - vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, - vmf->address, &vmf->ptl); - if (!pte_none(*vmf->pte)) { - update_mmu_tlb(vma, vmf->address, vmf->pte); - goto unlock; - } - ret = check_stable_address_space(vma->vm_mm); - if (ret) - goto unlock; - /* Deliver the page fault to userland, check inside PT lock */ - if (userfaultfd_missing(vma)) { - pte_unmap_unlock(vmf->pte, vmf->ptl); - return handle_userfault(vmf, VM_UFFD_MISSING); - } - goto setpte; + } else { + /* Allocate our own private page. */ + if (unlikely(anon_vma_prepare(vma))) + goto oom; + page = alloc_zeroed_user_highpage_movable(vma, vmf->address); + if (!page) + goto oom; + + if (mem_cgroup_charge(page, vma->vm_mm, GFP_KERNEL)) + goto oom_free_page; + cgroup_throttle_swaprate(page, GFP_KERNEL); + + /* + * The memory barrier inside __SetPageUptodate makes sure that + * preceding stores to the page contents become visible before + * the set_pte_at() write. + */ + __SetPageUptodate(page); + + entry = mk_pte(page, vma->vm_page_prot); + entry = pte_sw_mkyoung(entry); + if (vma->vm_flags & VM_WRITE) + entry = pte_mkwrite(pte_mkdirty(entry)); } - /* Allocate our own private page. */ - if (unlikely(anon_vma_prepare(vma))) - goto oom; - page = alloc_zeroed_user_highpage_movable(vma, vmf->address); - if (!page) - goto oom; - - if (mem_cgroup_charge(page, vma->vm_mm, GFP_KERNEL)) - goto oom_free_page; - cgroup_throttle_swaprate(page, GFP_KERNEL); - - /* - * The memory barrier inside __SetPageUptodate makes sure that - * preceding stores to the page contents become visible before - * the set_pte_at() write. - */ - __SetPageUptodate(page); - - entry = mk_pte(page, vma->vm_page_prot); - entry = pte_sw_mkyoung(entry); - if (vma->vm_flags & VM_WRITE) - entry = pte_mkwrite(pte_mkdirty(entry)); - vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, vmf->address, &vmf->ptl); if (!pte_none(*vmf->pte)) { update_mmu_tlb(vma, vmf->address, vmf->pte); - goto release; + goto unlock; } ret = check_stable_address_space(vma->vm_mm); if (ret) - goto release; + goto unlock; /* Deliver the page fault to userland, check inside PT lock */ if (userfaultfd_missing(vma)) { pte_unmap_unlock(vmf->pte, vmf->ptl); - put_page(page); + if (page) + put_page(page); return handle_userfault(vmf, VM_UFFD_MISSING); } - inc_mm_counter_fast(vma->vm_mm, MM_ANONPAGES); - page_add_new_anon_rmap(page, vma, vmf->address, false); - lru_cache_add_inactive_or_unevictable(page, vma); -setpte: + if (page) { + inc_mm_counter_fast(vma->vm_mm, MM_ANONPAGES); + page_add_new_anon_rmap(page, vma, vmf->address, false); + lru_cache_add_inactive_or_unevictable(page, vma); + } + set_pte_at(vma->vm_mm, vmf->address, vmf->pte, entry); /* No need to invalidate - it was non-present before */ update_mmu_cache(vma, vmf->address, vmf->pte); + pte_unmap_unlock(vmf->pte, vmf->ptl); + return 0; unlock: pte_unmap_unlock(vmf->pte, vmf->ptl); + if (page) + put_page(page); return ret; -release: - put_page(page); - goto unlock; oom_free_page: put_page(page); oom: