2024-04-22 18:12:38

by Jianfeng Wang

Subject: [PATCH] mm: huge_memory: convert __do_huge_pmd_anonymous_page() to use folios

Change __do_huge_pmd_anonymous_page() to take folio as input, as its
caller has used folio. Save one unnecessary call to compound_head().

Signed-off-by: Jianfeng Wang <[email protected]>
---
mm/huge_memory.c | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 89f58c7603b2..83566ee738e0 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -866,10 +866,9 @@ 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 folio *folio = page_folio(page);
pgtable_t pgtable;
unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
vm_fault_t ret = 0;
@@ -890,7 +889,7 @@ static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf,
goto release;
}

- clear_huge_page(page, vmf->address, HPAGE_PMD_NR);
+ clear_huge_page(&folio->page, vmf->address, HPAGE_PMD_NR);
/*
* The memory barrier inside __folio_mark_uptodate makes sure that
* clear_huge_page writes become visible before the set_pmd_at()
@@ -918,7 +917,7 @@ static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf,
return ret;
}

- entry = mk_huge_pmd(page, vma->vm_page_prot);
+ entry = mk_huge_pmd(&folio->page, vma->vm_page_prot);
entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
folio_add_new_anon_rmap(folio, vma, haddr);
folio_add_lru_vma(folio, vma);
@@ -1051,7 +1050,7 @@ 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,
--
2.42.1

2024-04-23 00:16:47

by Matthew Wilcox

Subject: Re: [PATCH] mm: huge_memory: convert __do_huge_pmd_anonymous_page() to use folios

On Mon, Apr 22, 2024 at 11:12:16AM -0700, Jianfeng Wang wrote:
> Change __do_huge_pmd_anonymous_page() to take folio as input, as its
> caller has used folio. Save one unnecessary call to compound_head().

I don't like this patch. It makes the assumption that folios will never
be larger than PMD size, and I don't think that's an assumption that's
going to last another five years. Look where you had to
do &folio->page:

> + clear_huge_page(&folio->page, vmf->address, HPAGE_PMD_NR);

> + entry = mk_huge_pmd(&folio->page, vma->vm_page_prot);

For mk_huge_pmd() in particular, you need to know the precise page, and
not just use the first page of the folio.