Re: [PATCH v2 2/3] hugetlb: Convert hugetlb_no_page() to use struct vm_fault

Vishal Moola
2024-04-08T17:45:35Z

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On Sun, Apr 07, 2024 at 04:59:13PM +0800, Muchun Song wrote:
>
>
> > On Apr 5, 2024, at 03:58, Vishal Moola <vishal.moola@gmail.com> wrote:
> >
> > On Thu, Apr 4, 2024 at 5:49 AM Oscar Salvador <osalvador@suse.de> wrote:
> >>
> >> On Mon, Apr 01, 2024 at 01:26:50PM -0700, Vishal Moola (Oracle) wrote:
> >>> hugetlb_no_page() can use the struct vm_fault passed in from
> >>> hugetlb_fault(). This alleviates the stack by consolidating 7
> >>> variables into a single struct.
> >>>
> >>> Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
> >>> ---
> >>> mm/hugetlb.c | 59 ++++++++++++++++++++++++++--------------------------
> >>> 1 file changed, 29 insertions(+), 30 deletions(-)
> >>>
> >>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> >>> index 360b82374a89..aca2f11b4138 100644
> >>> --- a/mm/hugetlb.c
> >>> +++ b/mm/hugetlb.c
> >>> @@ -6189,9 +6189,7 @@ static bool hugetlb_pte_stable(struct hstate *h, struct mm_struct *mm,
> >>>
> >>> static vm_fault_t hugetlb_no_page(struct mm_struct *mm,
> >>> struct vm_area_struct *vma,
> >>> - struct address_space *mapping, pgoff_t idx,
> >>> - unsigned long address, pte_t *ptep,
> >>> - pte_t old_pte, unsigned int flags,
> >>> + struct address_space *mapping,
> >>
> >> AFAICS all this can be self-contained in vm_fault struct.
> >> vmf->vma->mm and vmf->vma.
> >> I mean, if we want to convert this interface, why not going all the way?
> >>
> >> Looks a bit odd some fields yes while some others remain.
> >>
> >> Or am I missing something?
> >
> > Mainly just minimizing code churn, we would either unnecessarily
> > change multiple lines using vma or have to declare the variables
> > again anyways (or have extra churn I didn't like).
>
> I don't think adding some variables is a problem. I suppose the compiler
> could do some optimization for us. So I think it is better to pass
> only one argument vmf to hugetlb_no_page(). Otherwise, LGTM.

Alright we can get rid of the vm_area_struct and mm_struct arguments as
well.

Andrew, could you please fold the attached patch into this one?

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From 891e085115a06f638e238bea267d520bb2432fba Mon Sep 17 00:00:00 2001
From: "Vishal Moola (Oracle)" <vishal.moola@gmail.com>
Date: Mon, 8 Apr 2024 10:17:54 -0700
Subject: [PATCH 1/2] hugetlb: Simplify hugetlb_no_page() arguments

To simplify the function arguments, as suggested by Oscar and Muchun.

Suggested-by: Muchun Song <muchun.song@linux.dev>
Suggested-by: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
---
mm/hugetlb.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 456c81fbf8f5..05fe610f4699 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -6186,11 +6186,11 @@ static bool hugetlb_pte_stable(struct hstate *h, struct mm_struct *mm,
return same;
}

-static vm_fault_t hugetlb_no_page(struct mm_struct *mm,
- struct vm_area_struct *vma,
- struct address_space *mapping,
+static vm_fault_t hugetlb_no_page(struct address_space *mapping,
struct vm_fault *vmf)
{
+ struct vm_area_struct *vma = vmf->vma;
+ struct mm_struct *mm = vma->vm_mm;
struct hstate *h = hstate_vma(vma);
vm_fault_t ret = VM_FAULT_SIGBUS;
int anon_rmap = 0;
@@ -6483,7 +6483,7 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
* hugetlb_no_page will drop vma lock and hugetlb fault
* mutex internally, which make us return immediately.
*/
- return hugetlb_no_page(mm, vma, mapping, &vmf);
+ return hugetlb_no_page(mapping, &vmf);
}

ret = 0;
--
2.43.0