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SubjectRe: [PATCH v6 22/24] mm: Speculative page fault handler return VMA
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On 13/01/2018 05:23, Matthew Wilcox wrote:
> On Fri, Jan 12, 2018 at 11:02:51AM -0800, Matthew Wilcox wrote:
>> On Fri, Jan 12, 2018 at 06:26:06PM +0100, Laurent Dufour wrote:
>>> @@ -1354,7 +1354,10 @@ extern int handle_mm_fault(struct vm_area_struct *vma, unsigned long address,
>>> unsigned int flags);
>>> #ifdef CONFIG_SPF
>>> extern int handle_speculative_fault(struct mm_struct *mm,
>>> + unsigned long address, unsigned int flags,
>>> + struct vm_area_struct **vma);
>>
>> I think this shows that we need to create 'struct vm_fault' on the stack
>> in the arch code and then pass it to handle_speculative_fault(), followed
>> by handle_mm_fault(). That should be quite a nice cleanup actually.
>> I know that's only 30+ architectures to change ;-)
>
> Of course, we don't need to change them all. Try this:

That would be good candidate for a clean up but I'm not sure this should be
part of this already too long series.

If you don't mind, unless a global agreement is stated on that, I'd prefer
to postpone such a change once the initial series is accepted.

Cheers,
Laurent.

> Subject: [PATCH] Add vm_handle_fault
>
> For the speculative fault handler, we want to create the struct vm_fault
> on the stack in the arch code and pass it into the generic mm code.
> To avoid changing 30+ architectures, leave handle_mm_fault with its
> current function signature and move its guts into the new vm_handle_fault
> function. Even this saves a nice 172 bytes on the random x86-64 .config
> I happen to have around.
>
> Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
>
> diff --git a/mm/memory.c b/mm/memory.c
> index 5eb3d2524bdc..403934297a3d 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -3977,36 +3977,28 @@ static int handle_pte_fault(struct vm_fault *vmf)
> * The mmap_sem may have been released depending on flags and our
> * return value. See filemap_fault() and __lock_page_or_retry().
> */
> -static int __handle_mm_fault(struct vm_area_struct *vma, unsigned long address,
> - unsigned int flags)
> +static int __handle_mm_fault(struct vm_fault *vmf)
> {
> - struct vm_fault vmf = {
> - .vma = vma,
> - .address = address & PAGE_MASK,
> - .flags = flags,
> - .pgoff = linear_page_index(vma, address),
> - .gfp_mask = __get_fault_gfp_mask(vma),
> - };
> - unsigned int dirty = flags & FAULT_FLAG_WRITE;
> - struct mm_struct *mm = vma->vm_mm;
> + unsigned int dirty = vmf->flags & FAULT_FLAG_WRITE;
> + struct mm_struct *mm = vmf->vma->vm_mm;
> pgd_t *pgd;
> p4d_t *p4d;
> int ret;
>
> - pgd = pgd_offset(mm, address);
> - p4d = p4d_alloc(mm, pgd, address);
> + pgd = pgd_offset(mm, vmf->address);
> + p4d = p4d_alloc(mm, pgd, vmf->address);
> if (!p4d)
> return VM_FAULT_OOM;
>
> - vmf.pud = pud_alloc(mm, p4d, address);
> - if (!vmf.pud)
> + vmf->pud = pud_alloc(mm, p4d, vmf->address);
> + if (!vmf->pud)
> return VM_FAULT_OOM;
> - if (pud_none(*vmf.pud) && transparent_hugepage_enabled(vma)) {
> - ret = create_huge_pud(&vmf);
> + if (pud_none(*vmf->pud) && transparent_hugepage_enabled(vmf->vma)) {
> + ret = create_huge_pud(vmf);
> if (!(ret & VM_FAULT_FALLBACK))
> return ret;
> } else {
> - pud_t orig_pud = *vmf.pud;
> + pud_t orig_pud = *vmf->pud;
>
> barrier();
> if (pud_trans_huge(orig_pud) || pud_devmap(orig_pud)) {
> @@ -4014,50 +4006,51 @@ static int __handle_mm_fault(struct vm_area_struct *vma, unsigned long address,
> /* NUMA case for anonymous PUDs would go here */
>
> if (dirty && !pud_access_permitted(orig_pud, WRITE)) {
> - ret = wp_huge_pud(&vmf, orig_pud);
> + ret = wp_huge_pud(vmf, orig_pud);
> if (!(ret & VM_FAULT_FALLBACK))
> return ret;
> } else {
> - huge_pud_set_accessed(&vmf, orig_pud);
> + huge_pud_set_accessed(vmf, orig_pud);
> return 0;
> }
> }
> }
>
> - vmf.pmd = pmd_alloc(mm, vmf.pud, address);
> - if (!vmf.pmd)
> + vmf->pmd = pmd_alloc(mm, vmf->pud, vmf->address);
> + if (!vmf->pmd)
> return VM_FAULT_OOM;
> - if (pmd_none(*vmf.pmd) && transparent_hugepage_enabled(vma)) {
> - ret = create_huge_pmd(&vmf);
> + if (pmd_none(*vmf->pmd) && transparent_hugepage_enabled(vmf->vma)) {
> + ret = create_huge_pmd(vmf);
> if (!(ret & VM_FAULT_FALLBACK))
> return ret;
> } else {
> - pmd_t orig_pmd = *vmf.pmd;
> + pmd_t orig_pmd = *vmf->pmd;
>
> barrier();
> if (unlikely(is_swap_pmd(orig_pmd))) {
> VM_BUG_ON(thp_migration_supported() &&
> !is_pmd_migration_entry(orig_pmd));
> if (is_pmd_migration_entry(orig_pmd))
> - pmd_migration_entry_wait(mm, vmf.pmd);
> + pmd_migration_entry_wait(mm, vmf->pmd);
> return 0;
> }
> if (pmd_trans_huge(orig_pmd) || pmd_devmap(orig_pmd)) {
> - if (pmd_protnone(orig_pmd) && vma_is_accessible(vma))
> - return do_huge_pmd_numa_page(&vmf, orig_pmd);
> + if (pmd_protnone(orig_pmd) &&
> + vma_is_accessible(vmf->vma))
> + return do_huge_pmd_numa_page(vmf, orig_pmd);
>
> if (dirty && !pmd_access_permitted(orig_pmd, WRITE)) {
> - ret = wp_huge_pmd(&vmf, orig_pmd);
> + ret = wp_huge_pmd(vmf, orig_pmd);
> if (!(ret & VM_FAULT_FALLBACK))
> return ret;
> } else {
> - huge_pmd_set_accessed(&vmf, orig_pmd);
> + huge_pmd_set_accessed(vmf, orig_pmd);
> return 0;
> }
> }
> }
>
> - return handle_pte_fault(&vmf);
> + return handle_pte_fault(vmf);
> }
>
> /*
> @@ -4066,9 +4059,10 @@ static int __handle_mm_fault(struct vm_area_struct *vma, unsigned long address,
> * The mmap_sem may have been released depending on flags and our
> * return value. See filemap_fault() and __lock_page_or_retry().
> */
> -int handle_mm_fault(struct vm_area_struct *vma, unsigned long address,
> - unsigned int flags)
> +int vm_handle_fault(struct vm_fault *vmf)
> {
> + unsigned int flags = vmf->flags;
> + struct vm_area_struct *vma = vmf->vma;
> int ret;
>
> __set_current_state(TASK_RUNNING);
> @@ -4092,9 +4086,9 @@ int handle_mm_fault(struct vm_area_struct *vma, unsigned long address,
> mem_cgroup_oom_enable();
>
> if (unlikely(is_vm_hugetlb_page(vma)))
> - ret = hugetlb_fault(vma->vm_mm, vma, address, flags);
> + ret = hugetlb_fault(vma->vm_mm, vma, vmf->address, flags);
> else
> - ret = __handle_mm_fault(vma, address, flags);
> + ret = __handle_mm_fault(vmf);
>
> if (flags & FAULT_FLAG_USER) {
> mem_cgroup_oom_disable();
> @@ -4110,6 +4104,26 @@ int handle_mm_fault(struct vm_area_struct *vma, unsigned long address,
>
> return ret;
> }
> +
> +/*
> + * By the time we get here, we already hold the mm semaphore
> + *
> + * The mmap_sem may have been released depending on flags and our
> + * return value. See filemap_fault() and __lock_page_or_retry().
> + */
> +int handle_mm_fault(struct vm_area_struct *vma, unsigned long address,
> + unsigned int flags)
> +{
> + struct vm_fault vmf = {
> + .vma = vma,
> + .address = address & PAGE_MASK,
> + .flags = flags,
> + .pgoff = linear_page_index(vma, address),
> + .gfp_mask = __get_fault_gfp_mask(vma),
> + };
> +
> + return vm_handle_fault(&vmf);
> +}
> EXPORT_SYMBOL_GPL(handle_mm_fault);
>
> #ifndef __PAGETABLE_P4D_FOLDED
>

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