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Date: Thu, 24 Oct 2019 21:06:55 +0800
From: Zong Li <zongbox@...il.com>
To: Steven Price <steven.price@....com>
Cc: linux-mm@...ck.org, Andy Lutomirski <luto@...nel.org>,
Ard Biesheuvel <ard.biesheuvel@...aro.org>,
Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>,
Catalin Marinas <catalin.marinas@....com>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Ingo Molnar <mingo@...hat.com>,
James Morse <james.morse@....com>,
Jérôme Glisse <jglisse@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
Thomas Gleixner <tglx@...utronix.de>,
Will Deacon <will@...nel.org>, x86@...nel.org,
"H. Peter Anvin" <hpa@...or.com>,
linux-arm-kernel@...ts.infradead.org,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Mark Rutland <Mark.Rutland@....com>,
"Liang, Kan" <kan.liang@...ux.intel.com>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v12 11/22] mm: pagewalk: Add p4d_entry() and pgd_entry()
Steven Price <steven.price@....com> 於 2019年10月19日 週六 下午4:14寫道：
>
> pgd_entry() and pud_entry() were removed by commit 0b1fbfe50006c410
> ("mm/pagewalk: remove pgd_entry() and pud_entry()") because there were
> no users. We're about to add users so reintroduce them, along with
> p4d_entry() as we now have 5 levels of tables.
>
> Note that commit a00cc7d9dd93d66a ("mm, x86: add support for
> PUD-sized transparent hugepages") already re-added pud_entry() but with
> different semantics to the other callbacks. Since there have never
> been upstream users of this, revert the semantics back to match the
> other callbacks. This means pud_entry() is called for all entries, not
> just transparent huge pages.
>
> Signed-off-by: Steven Price <steven.price@....com>
> ---
> include/linux/pagewalk.h | 19 +++++++++++++------
> mm/pagewalk.c | 27 ++++++++++++++++-----------
> 2 files changed, 29 insertions(+), 17 deletions(-)
>
> diff --git a/include/linux/pagewalk.h b/include/linux/pagewalk.h
> index bddd9759bab9..12004b097eae 100644
> --- a/include/linux/pagewalk.h
> +++ b/include/linux/pagewalk.h
> @@ -8,15 +8,15 @@ struct mm_walk;
>
> /**
> * mm_walk_ops - callbacks for walk_page_range
> - * @pud_entry: if set, called for each non-empty PUD (2nd-level) entry
> - * this handler should only handle pud_trans_huge() puds.
> - * the pmd_entry or pte_entry callbacks will be used for
> - * regular PUDs.
> - * @pmd_entry: if set, called for each non-empty PMD (3rd-level) entry
> + * @pgd_entry: if set, called for each non-empty PGD (top-level) entry
> + * @p4d_entry: if set, called for each non-empty P4D entry
> + * @pud_entry: if set, called for each non-empty PUD entry
> + * @pmd_entry: if set, called for each non-empty PMD entry
> * this handler is required to be able to handle
> * pmd_trans_huge() pmds. They may simply choose to
> * split_huge_page() instead of handling it explicitly.
> - * @pte_entry: if set, called for each non-empty PTE (4th-level) entry
> + * @pte_entry: if set, called for each non-empty PTE (lowest-level)
> + * entry
> * @pte_hole: if set, called for each hole at all levels
> * @hugetlb_entry: if set, called for each hugetlb entry
> * @test_walk: caller specific callback function to determine whether
> @@ -24,8 +24,15 @@ struct mm_walk;
> * "do page table walk over the current vma", returning
> * a negative value means "abort current page table walk
> * right now" and returning 1 means "skip the current vma"
> + *
> + * p?d_entry callbacks are called even if those levels are folded on a
> + * particular architecture/configuration.
> */
> struct mm_walk_ops {
> + int (*pgd_entry)(pgd_t *pgd, unsigned long addr,
> + unsigned long next, struct mm_walk *walk);
> + int (*p4d_entry)(p4d_t *p4d, unsigned long addr,
> + unsigned long next, struct mm_walk *walk);
> int (*pud_entry)(pud_t *pud, unsigned long addr,
> unsigned long next, struct mm_walk *walk);
> int (*pmd_entry)(pmd_t *pmd, unsigned long addr,
> diff --git a/mm/pagewalk.c b/mm/pagewalk.c
> index d48c2a986ea3..fc4d98a3a5a0 100644
> --- a/mm/pagewalk.c
> +++ b/mm/pagewalk.c
> @@ -93,15 +93,9 @@ static int walk_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end,
> }
>
> if (ops->pud_entry) {
> - spinlock_t *ptl = pud_trans_huge_lock(pud, walk->vma);
> -
> - if (ptl) {
> - err = ops->pud_entry(pud, addr, next, walk);
> - spin_unlock(ptl);
> - if (err)
> - break;
> - continue;
> - }
> + err = ops->pud_entry(pud, addr, next, walk);
> + if (err)
> + break;
> }
>
> split_huge_pud(walk->vma, pud, addr);
> @@ -135,7 +129,12 @@ static int walk_p4d_range(pgd_t *pgd, unsigned long addr, unsigned long end,
> break;
> continue;
> }
> - if (ops->pmd_entry || ops->pte_entry)
> + if (ops->p4d_entry) {
> + err = ops->p4d_entry(p4d, addr, next, walk);
> + if (err)
> + break;
> + }
> + if (ops->pud_entry || ops->pmd_entry || ops->pte_entry)
> err = walk_pud_range(p4d, addr, next, walk);
> if (err)
> break;
> @@ -162,7 +161,13 @@ static int walk_pgd_range(unsigned long addr, unsigned long end,
> break;
> continue;
> }
> - if (ops->pmd_entry || ops->pte_entry)
> + if (ops->pgd_entry) {
> + err = ops->pgd_entry(pgd, addr, next, walk);
> + if (err)
> + break;
> + }
> + if (ops->p4d_entry || ops->pud_entry || ops->pmd_entry ||
> + ops->pte_entry)
> err = walk_p4d_range(pgd, addr, next, walk);
> if (err)
> break;
> --
> 2.20.1
>
It's good to me.
Tested-by: Zong Li <zong.li@...ive.com>
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