| Message ID | 20230112083006.163393-2-wangkefeng.wang@huawei.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm: remove cgroup_throttle_swaprate() completely | expand |
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(). >
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index c13b1f67d14e..cb23b24e2eb8 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -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,
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(-)