[-next,1/7] mm: huge_memory: make __do_huge_pmd_anonymous_page() to take a folio
Commit Message
Let's __do_huge_pmd_anonymous_page() take a folio and convert related
functions to use folios.
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
---
mm/huge_memory.c | 23 ++++++++++++-----------
1 file changed, 12 insertions(+), 11 deletions(-)
Comments
On Thu, Jan 12, 2023 at 04:30:00PM +0800, Kefeng Wang wrote:
> Let's __do_huge_pmd_anonymous_page() take a folio and convert related
> functions to use folios.
No, this is actively wrong! Andrew, please drop this patch.
If we want to support folio sizes larger than PMD size (and I think we
do), we need to be able to specify precisely which page in the folio
is to be stored at this PTE. The *interface* must remain struct page.
We can convert from page to folio within the function, but we *MUST NOT*
go the other way.
> static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf,
> - struct page *page, gfp_t gfp)
> + struct folio *folio, gfp_t gfp)
> {
> struct vm_area_struct *vma = vmf->vma;
> + struct page *page = &folio->page;
... ie this is bad and wrong.
> @@ -834,7 +835,7 @@ vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf)
> count_vm_event(THP_FAULT_FALLBACK);
> return VM_FAULT_FALLBACK;
> }
> - return __do_huge_pmd_anonymous_page(vmf, &folio->page, gfp);
> + return __do_huge_pmd_anonymous_page(vmf, folio, gfp);
> }
>
> static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
A reasonable person might ask "But Matthew, you allocated a folio here,
then you're converting back to a struct page to call
__do_huge_pmd_anonymous_page() so isn't this a sensible patch?"
And I would say "still no". This is a question of interfaces, and
even though __do_huge_pmd_anonymous_page() is static and has precisely
one caller today that always allocates a folio of precisely PMD size,
I suspect it will need to be more visible in the future and the
conversion of the interface from page to folio misleads people.
On 2023/1/13 22:25, Matthew Wilcox wrote:
> On Thu, Jan 12, 2023 at 04:30:00PM +0800, Kefeng Wang wrote:
>> Let's __do_huge_pmd_anonymous_page() take a folio and convert related
>> functions to use folios.
>
> No, this is actively wrong! Andrew, please drop this patch.
>
> If we want to support folio sizes larger than PMD size (and I think we
> do), we need to be able to specify precisely which page in the folio
> is to be stored at this PTE. The *interface* must remain struct page.
> We can convert from page to folio within the function, but we *MUST NOT*
> go the other way.
Got it,
>
>> static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf,
>> - struct page *page, gfp_t gfp)
>> + struct folio *folio, gfp_t gfp)
>> {
>> struct vm_area_struct *vma = vmf->vma;
>> + struct page *page = &folio->page;
>
> ... ie this is bad and wrong.
>
>> @@ -834,7 +835,7 @@ vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf)
>> count_vm_event(THP_FAULT_FALLBACK);
>> return VM_FAULT_FALLBACK;
>> }
>> - return __do_huge_pmd_anonymous_page(vmf, &folio->page, gfp);
>> + return __do_huge_pmd_anonymous_page(vmf, folio, gfp);
>> }
>>
>> static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
>
> A reasonable person might ask "But Matthew, you allocated a folio here,
> then you're converting back to a struct page to call
> __do_huge_pmd_anonymous_page() so isn't this a sensible patch?"
and this is why I change the parameter from page to folio(no need to go
back and forth between page and folio),
>
> And I would say "still no". This is a question of interfaces, and
> even though __do_huge_pmd_anonymous_page() is static and has precisely
> one caller today that always allocates a folio of precisely PMD size,
> I suspect it will need to be more visible in the future and the
> conversion of the interface from page to folio misleads people.
ok, will keep page for __do_huge_pmd_anonymous_page().
>
@@ -650,22 +650,23 @@ unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr,
EXPORT_SYMBOL_GPL(thp_get_unmapped_area);
static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf,
- struct page *page, gfp_t gfp)
+ struct folio *folio, gfp_t gfp)
{
struct vm_area_struct *vma = vmf->vma;
+ struct page *page = &folio->page;
pgtable_t pgtable;
unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
vm_fault_t ret = 0;
- VM_BUG_ON_PAGE(!PageCompound(page), page);
+ VM_BUG_ON_FOLIO(!folio_test_large(folio), folio);
- if (mem_cgroup_charge(page_folio(page), vma->vm_mm, gfp)) {
- put_page(page);
+ if (mem_cgroup_charge(folio, vma->vm_mm, gfp)) {
+ folio_put(folio);
count_vm_event(THP_FAULT_FALLBACK);
count_vm_event(THP_FAULT_FALLBACK_CHARGE);
return VM_FAULT_FALLBACK;
}
- cgroup_throttle_swaprate(page, gfp);
+ folio_throttle_swaprate(folio, gfp);
pgtable = pte_alloc_one(vma->vm_mm);
if (unlikely(!pgtable)) {
@@ -675,11 +676,11 @@ static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf,
clear_huge_page(page, vmf->address, HPAGE_PMD_NR);
/*
- * The memory barrier inside __SetPageUptodate makes sure that
+ * The memory barrier inside __folio_mark_uptodate makes sure that
* clear_huge_page writes become visible before the set_pmd_at()
* write.
*/
- __SetPageUptodate(page);
+ __folio_mark_uptodate(folio);
vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
if (unlikely(!pmd_none(*vmf->pmd))) {
@@ -694,7 +695,7 @@ static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf,
/* Deliver the page fault to userland */
if (userfaultfd_missing(vma)) {
spin_unlock(vmf->ptl);
- put_page(page);
+ folio_put(folio);
pte_free(vma->vm_mm, pgtable);
ret = handle_userfault(vmf, VM_UFFD_MISSING);
VM_BUG_ON(ret & VM_FAULT_FALLBACK);
@@ -704,7 +705,7 @@ static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf,
entry = mk_huge_pmd(page, vma->vm_page_prot);
entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
page_add_new_anon_rmap(page, vma, haddr);
- lru_cache_add_inactive_or_unevictable(page, vma);
+ folio_add_lru_vma(folio, vma);
pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable);
set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
@@ -721,7 +722,7 @@ static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf,
release:
if (pgtable)
pte_free(vma->vm_mm, pgtable);
- put_page(page);
+ folio_put(folio);
return ret;
}
@@ -834,7 +835,7 @@ vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf)
count_vm_event(THP_FAULT_FALLBACK);
return VM_FAULT_FALLBACK;
}
- return __do_huge_pmd_anonymous_page(vmf, &folio->page, gfp);
+ return __do_huge_pmd_anonymous_page(vmf, folio, gfp);
}
static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,