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SubjectRe: [PATCH v9 11/24] mm: Cache some VMA fields in the vm_fault structure
On Tue, 13 Mar 2018, Laurent Dufour wrote:

> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index ef6ef0627090..dfa81a638b7c 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -359,6 +359,12 @@ struct vm_fault {
> * page table to avoid allocation from
> * atomic context.
> */
> + /*
> + * These entries are required when handling speculative page fault.
> + * This way the page handling is done using consistent field values.
> + */
> + unsigned long vma_flags;
> + pgprot_t vma_page_prot;
> };
>
> /* page entry size for vm->huge_fault() */
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 446427cafa19..f71db2b42b30 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -3717,6 +3717,8 @@ static int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
> .vma = vma,
> .address = address,
> .flags = flags,
> + .vma_flags = vma->vm_flags,
> + .vma_page_prot = vma->vm_page_prot,
> /*
> * Hard to debug if it ends up being
> * used by a callee that assumes
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index 32314e9e48dd..a946d5306160 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -882,6 +882,8 @@ static bool __collapse_huge_page_swapin(struct mm_struct *mm,
> .flags = FAULT_FLAG_ALLOW_RETRY,
> .pmd = pmd,
> .pgoff = linear_page_index(vma, address),
> + .vma_flags = vma->vm_flags,
> + .vma_page_prot = vma->vm_page_prot,
> };
>
> /* we only decide to swapin, if there is enough young ptes */
> diff --git a/mm/memory.c b/mm/memory.c
> index 0200340ef089..46fe92b93682 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -2615,7 +2615,7 @@ static int wp_page_copy(struct vm_fault *vmf)
> * Don't let another task, with possibly unlocked vma,
> * keep the mlocked page.
> */
> - if (page_copied && (vma->vm_flags & VM_LOCKED)) {
> + if (page_copied && (vmf->vma_flags & VM_LOCKED)) {
> lock_page(old_page); /* LRU manipulation */
> if (PageMlocked(old_page))
> munlock_vma_page(old_page);

Doesn't wp_page_copy() also need to pass this to anon_vma_prepare() so
that find_mergeable_anon_vma() works correctly?

> @@ -2649,7 +2649,7 @@ static int wp_page_copy(struct vm_fault *vmf)
> */
> int finish_mkwrite_fault(struct vm_fault *vmf)
> {
> - WARN_ON_ONCE(!(vmf->vma->vm_flags & VM_SHARED));
> + WARN_ON_ONCE(!(vmf->vma_flags & VM_SHARED));
> if (!pte_map_lock(vmf))
> return VM_FAULT_RETRY;
> /*
> @@ -2751,7 +2751,7 @@ static int do_wp_page(struct vm_fault *vmf)
> * We should not cow pages in a shared writeable mapping.
> * Just mark the pages writable and/or call ops->pfn_mkwrite.
> */
> - if ((vma->vm_flags & (VM_WRITE|VM_SHARED)) ==
> + if ((vmf->vma_flags & (VM_WRITE|VM_SHARED)) ==
> (VM_WRITE|VM_SHARED))
> return wp_pfn_shared(vmf);
>
> @@ -2798,7 +2798,7 @@ static int do_wp_page(struct vm_fault *vmf)
> return VM_FAULT_WRITE;
> }
> unlock_page(vmf->page);
> - } else if (unlikely((vma->vm_flags & (VM_WRITE|VM_SHARED)) ==
> + } else if (unlikely((vmf->vma_flags & (VM_WRITE|VM_SHARED)) ==
> (VM_WRITE|VM_SHARED))) {
> return wp_page_shared(vmf);
> }
> @@ -3067,7 +3067,7 @@ int do_swap_page(struct vm_fault *vmf)
>
> inc_mm_counter_fast(vma->vm_mm, MM_ANONPAGES);
> dec_mm_counter_fast(vma->vm_mm, MM_SWAPENTS);
> - pte = mk_pte(page, vma->vm_page_prot);
> + pte = mk_pte(page, vmf->vma_page_prot);
> if ((vmf->flags & FAULT_FLAG_WRITE) && reuse_swap_page(page, NULL)) {
> pte = maybe_mkwrite(pte_mkdirty(pte), vma);
> vmf->flags &= ~FAULT_FLAG_WRITE;
> @@ -3093,7 +3093,7 @@ int do_swap_page(struct vm_fault *vmf)
>
> swap_free(entry);
> if (mem_cgroup_swap_full(page) ||
> - (vma->vm_flags & VM_LOCKED) || PageMlocked(page))
> + (vmf->vma_flags & VM_LOCKED) || PageMlocked(page))
> try_to_free_swap(page);
> unlock_page(page);
> if (page != swapcache && swapcache) {
> @@ -3150,7 +3150,7 @@ static int do_anonymous_page(struct vm_fault *vmf)
> pte_t entry;
>
> /* File mapping without ->vm_ops ? */
> - if (vma->vm_flags & VM_SHARED)
> + if (vmf->vma_flags & VM_SHARED)
> return VM_FAULT_SIGBUS;
>
> /*
> @@ -3174,7 +3174,7 @@ static int do_anonymous_page(struct vm_fault *vmf)
> if (!(vmf->flags & FAULT_FLAG_WRITE) &&
> !mm_forbids_zeropage(vma->vm_mm)) {
> entry = pte_mkspecial(pfn_pte(my_zero_pfn(vmf->address),
> - vma->vm_page_prot));
> + vmf->vma_page_prot));
> if (!pte_map_lock(vmf))
> return VM_FAULT_RETRY;
> if (!pte_none(*vmf->pte))
> @@ -3207,8 +3207,8 @@ static int do_anonymous_page(struct vm_fault *vmf)
> */
> __SetPageUptodate(page);
>
> - entry = mk_pte(page, vma->vm_page_prot);
> - if (vma->vm_flags & VM_WRITE)
> + entry = mk_pte(page, vmf->vma_page_prot);
> + if (vmf->vma_flags & VM_WRITE)
> entry = pte_mkwrite(pte_mkdirty(entry));
>
> if (!pte_map_lock(vmf)) {
> @@ -3404,7 +3404,7 @@ static int do_set_pmd(struct vm_fault *vmf, struct page *page)
> for (i = 0; i < HPAGE_PMD_NR; i++)
> flush_icache_page(vma, page + i);
>
> - entry = mk_huge_pmd(page, vma->vm_page_prot);
> + entry = mk_huge_pmd(page, vmf->vma_page_prot);
> if (write)
> entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
>
> @@ -3478,11 +3478,11 @@ int alloc_set_pte(struct vm_fault *vmf, struct mem_cgroup *memcg,
> return VM_FAULT_NOPAGE;
>
> flush_icache_page(vma, page);
> - entry = mk_pte(page, vma->vm_page_prot);
> + entry = mk_pte(page, vmf->vma_page_prot);
> if (write)
> entry = maybe_mkwrite(pte_mkdirty(entry), vma);
> /* copy-on-write page */
> - if (write && !(vma->vm_flags & VM_SHARED)) {
> + if (write && !(vmf->vma_flags & VM_SHARED)) {
> inc_mm_counter_fast(vma->vm_mm, MM_ANONPAGES);
> page_add_new_anon_rmap(page, vma, vmf->address, false);
> mem_cgroup_commit_charge(page, memcg, false, false);
> @@ -3521,7 +3521,7 @@ int finish_fault(struct vm_fault *vmf)
>
> /* Did we COW the page? */
> if ((vmf->flags & FAULT_FLAG_WRITE) &&
> - !(vmf->vma->vm_flags & VM_SHARED))
> + !(vmf->vma_flags & VM_SHARED))
> page = vmf->cow_page;
> else
> page = vmf->page;
> @@ -3775,7 +3775,7 @@ static int do_fault(struct vm_fault *vmf)
> ret = VM_FAULT_SIGBUS;
> else if (!(vmf->flags & FAULT_FLAG_WRITE))
> ret = do_read_fault(vmf);
> - else if (!(vma->vm_flags & VM_SHARED))
> + else if (!(vmf->vma_flags & VM_SHARED))
> ret = do_cow_fault(vmf);
> else
> ret = do_shared_fault(vmf);
> @@ -3832,7 +3832,7 @@ static int do_numa_page(struct vm_fault *vmf)
> * accessible ptes, some can allow access by kernel mode.
> */
> pte = ptep_modify_prot_start(vma->vm_mm, vmf->address, vmf->pte);
> - pte = pte_modify(pte, vma->vm_page_prot);
> + pte = pte_modify(pte, vmf->vma_page_prot);
> pte = pte_mkyoung(pte);
> if (was_writable)
> pte = pte_mkwrite(pte);
> @@ -3866,7 +3866,7 @@ static int do_numa_page(struct vm_fault *vmf)
> * Flag if the page is shared between multiple address spaces. This
> * is later used when determining whether to group tasks together
> */
> - if (page_mapcount(page) > 1 && (vma->vm_flags & VM_SHARED))
> + if (page_mapcount(page) > 1 && (vmf->vma_flags & VM_SHARED))
> flags |= TNF_SHARED;
>
> last_cpupid = page_cpupid_last(page);
> @@ -3911,7 +3911,7 @@ static inline int wp_huge_pmd(struct vm_fault *vmf, pmd_t orig_pmd)
> return vmf->vma->vm_ops->huge_fault(vmf, PE_SIZE_PMD);
>
> /* COW handled on pte level: split pmd */
> - VM_BUG_ON_VMA(vmf->vma->vm_flags & VM_SHARED, vmf->vma);
> + VM_BUG_ON_VMA(vmf->vma_flags & VM_SHARED, vmf->vma);
> __split_huge_pmd(vmf->vma, vmf->pmd, vmf->address, false, NULL);
>
> return VM_FAULT_FALLBACK;
> @@ -4058,6 +4058,8 @@ static int __handle_mm_fault(struct vm_area_struct *vma, unsigned long address,
> .flags = flags,
> .pgoff = linear_page_index(vma, address),
> .gfp_mask = __get_fault_gfp_mask(vma),
> + .vma_flags = vma->vm_flags,
> + .vma_page_prot = vma->vm_page_prot,
> };
> unsigned int dirty = flags & FAULT_FLAG_WRITE;
> struct mm_struct *mm = vma->vm_mm;

Don't you also need to do this?

diff --git a/include/linux/mm.h b/include/linux/mm.h
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -694,9 +694,9 @@ void free_compound_page(struct page *page);
* pte_mkwrite. But get_user_pages can cause write faults for mappings
* that do not have writing enabled, when used by access_process_vm.
*/
-static inline pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma)
+static inline pte_t maybe_mkwrite(pte_t pte, unsigned long vma_flags)
{
- if (likely(vma->vm_flags & VM_WRITE))
+ if (likely(vma_flags & VM_WRITE))
pte = pte_mkwrite(pte);
return pte;
}
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1195,8 +1195,8 @@ static int do_huge_pmd_wp_page_fallback(struct vm_fault *vmf, pmd_t orig_pmd,

for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
pte_t entry;
- entry = mk_pte(pages[i], vma->vm_page_prot);
- entry = maybe_mkwrite(pte_mkdirty(entry), vma);
+ entry = mk_pte(pages[i], vmf->vma_page_prot);
+ entry = maybe_mkwrite(pte_mkdirty(entry), vmf->vma_flags);
memcg = (void *)page_private(pages[i]);
set_page_private(pages[i], 0);
page_add_new_anon_rmap(pages[i], vmf->vma, haddr, false);
@@ -2169,7 +2169,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
entry = pte_swp_mksoft_dirty(entry);
} else {
entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot));
- entry = maybe_mkwrite(entry, vma);
+ entry = maybe_mkwrite(entry, vma->vm_flags);
if (!write)
entry = pte_wrprotect(entry);
if (!young)
diff --git a/mm/memory.c b/mm/memory.c
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1826,7 +1826,7 @@ static int insert_pfn(struct vm_area_struct *vma, unsigned long addr,
out_mkwrite:
if (mkwrite) {
entry = pte_mkyoung(entry);
- entry = maybe_mkwrite(pte_mkdirty(entry), vma);
+ entry = maybe_mkwrite(pte_mkdirty(entry), vma->vm_flags);
}

set_pte_at(mm, addr, pte, entry);
@@ -2472,7 +2472,7 @@ static inline void wp_page_reuse(struct vm_fault *vmf)

flush_cache_page(vma, vmf->address, pte_pfn(vmf->orig_pte));
entry = pte_mkyoung(vmf->orig_pte);
- entry = maybe_mkwrite(pte_mkdirty(entry), vma);
+ entry = maybe_mkwrite(pte_mkdirty(entry), vmf->vma_flags);
if (ptep_set_access_flags(vma, vmf->address, vmf->pte, entry, 1))
update_mmu_cache(vma, vmf->address, vmf->pte);
pte_unmap_unlock(vmf->pte, vmf->ptl);
@@ -2549,8 +2549,8 @@ static int wp_page_copy(struct vm_fault *vmf)
inc_mm_counter_fast(mm, MM_ANONPAGES);
}
flush_cache_page(vma, vmf->address, pte_pfn(vmf->orig_pte));
- entry = mk_pte(new_page, vma->vm_page_prot);
- entry = maybe_mkwrite(pte_mkdirty(entry), vma);
+ entry = mk_pte(new_page, vmf->vma_page_prot);
+ entry = maybe_mkwrite(pte_mkdirty(entry), vmf->vma_flags);
/*
* Clear the pte entry and flush it first, before updating the
* pte with the new entry. This will avoid a race condition
@@ -3069,7 +3069,7 @@ int do_swap_page(struct vm_fault *vmf)
dec_mm_counter_fast(vma->vm_mm, MM_SWAPENTS);
pte = mk_pte(page, vmf->vma_page_prot);
if ((vmf->flags & FAULT_FLAG_WRITE) && reuse_swap_page(page, NULL)) {
- pte = maybe_mkwrite(pte_mkdirty(pte), vma);
+ pte = maybe_mkwrite(pte_mkdirty(pte), vmf->vm_flags);
vmf->flags &= ~FAULT_FLAG_WRITE;
ret |= VM_FAULT_WRITE;
exclusive = RMAP_EXCLUSIVE;
@@ -3481,7 +3481,7 @@ int alloc_set_pte(struct vm_fault *vmf, struct mem_cgroup *memcg,
flush_icache_page(vma, page);
entry = mk_pte(page, vmf->vma_page_prot);
if (write)
- entry = maybe_mkwrite(pte_mkdirty(entry), vma);
+ entry = maybe_mkwrite(pte_mkdirty(entry), vmf->vm_flags);
/* copy-on-write page */
if (write && !(vmf->vma_flags & VM_SHARED)) {
inc_mm_counter_fast(vma->vm_mm, MM_ANONPAGES);
diff --git a/mm/migrate.c b/mm/migrate.c
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -240,7 +240,7 @@ static bool remove_migration_pte(struct page *page, struct vm_area_struct *vma,
*/
entry = pte_to_swp_entry(*pvmw.pte);
if (is_write_migration_entry(entry))
- pte = maybe_mkwrite(pte, vma);
+ pte = maybe_mkwrite(pte, vma->vm_flags);

if (unlikely(is_zone_device_page(new))) {
if (is_device_private_page(new)) {
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