Commit ae075629 authored by Baolin Wang's avatar Baolin Wang Committed by Andrew Morton
Browse files

mm: change huge_ptep_clear_flush() to return the original pte 

Patch series "Fix CONT-PTE/PMD size hugetlb issue when unmapping or migrating", v4.

presently, migrating a hugetlb page or unmapping a poisoned hugetlb page,
we'll use ptep_clear_flush() and set_pte_at() to nuke the page table entry
and remap it, and this is incorrect for CONT-PTE or CONT-PMD size hugetlb
page, which will cause potential data consistent issue.  This patch set
will change to use hugetlb related APIs to fix this issue.

Note: Mike pointed out the huge_ptep_get() will only return the one
specific value, and it would not take into account the dirty or young bits
of CONT-PTE/PMDs like the huge_ptep_get_and_clear() [1].  This
inconsistent issue is not introduced by this patch set, and this issue
will be addressed in another thread [2].  Meanwhile the uffd for hugetlb
case [3] pointed out by Gerald also needs another patch to address.

[1] https://lore.kernel.org/linux-mm/85bd80b4-b4fd-0d3f-a2e5-149559f2f387@oracle.com/
[2] https://lore.kernel.org/all/cover.1651998586.git.baolin.wang@linux.alibaba.com/
[3] https://lore.kernel.org/linux-mm/20220503120343.6264e126@thinkpad/


This patch (of 3):

It is incorrect to use ptep_clear_flush() to nuke a hugetlb page table
when unmapping or migrating a hugetlb page, and will change to use
huge_ptep_clear_flush() instead in the following patches.

So this is a preparation patch, which changes the huge_ptep_clear_flush()
to return the original pte to help to nuke a hugetlb page table.

[baolin.wang@linux.alibaba.com: fix build in several more architectures]
  Link: https://lkml.kernel.org/r/0009a4cd-2826-e8be-e671-f050d4f18d5d@linux.alibaba.com
[sfr@canb.auug.org.au: fixup]
  Link: https://lkml.kernel.org/r/20220511181531.7f27a5c1@canb.auug.org.au
Link: https://lkml.kernel.org/r/cover.1652270205.git.baolin.wang@linux.alibaba.com
Link: https://lkml.kernel.org/r/20f77ddab90baa249bd24504c413189b82acde69.1652270205.git.baolin.wang@linux.alibaba.com
Link: https://lkml.kernel.org/r/cover.1652147571.git.baolin.wang@linux.alibaba.com
Link: https://lkml.kernel.org/r/dcf065868cce35bceaf138613ad27f17bb7c0c19.1652147571.git.baolin.wang@linux.alibaba.com


Signed-off-by: default avatarBaolin Wang <baolin.wang@linux.alibaba.com>
Signed-off-by: default avatarStephen Rothwell <sfr@canb.auug.org.au>
Acked-by: default avatarMike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: default avatarMuchun Song <songmuchun@bytedance.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Yoshinori Sato <ysato@users.osdn.me>
Cc: Rich Felker <dalias@libc.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 110bf7a5

arch/arm64/include/asm/hugetlb.h

+2 −2
Original line number Diff line number Diff line
@@ -39,7 +39,7 @@ extern pte_t huge_ptep_get_and_clear(struct mm_struct *mm, 
extern void huge_ptep_set_wrprotect(struct mm_struct *mm,

				    unsigned long addr, pte_t *ptep);

#define __HAVE_ARCH_HUGE_PTEP_CLEAR_FLUSH

extern void huge_ptep_clear_flush(struct vm_area_struct *vma,

extern pte_t huge_ptep_clear_flush(struct vm_area_struct *vma,

				   unsigned long addr, pte_t *ptep);

#define __HAVE_ARCH_HUGE_PTE_CLEAR

extern void huge_pte_clear(struct mm_struct *mm, unsigned long addr,

arch/arm64/mm/hugetlbpage.c

+5 −7
Original line number Diff line number Diff line
@@ -486,19 +486,17 @@ void huge_ptep_set_wrprotect(struct mm_struct *mm, 
		set_pte_at(mm, addr, ptep, pfn_pte(pfn, hugeprot));

}



void huge_ptep_clear_flush(struct vm_area_struct *vma,

pte_t huge_ptep_clear_flush(struct vm_area_struct *vma,

			    unsigned long addr, pte_t *ptep)

{

	size_t pgsize;

	int ncontig;



	if (!pte_cont(READ_ONCE(*ptep))) {

		ptep_clear_flush(vma, addr, ptep);

		return;

	}

	if (!pte_cont(READ_ONCE(*ptep)))

		return ptep_clear_flush(vma, addr, ptep);



	ncontig = find_num_contig(vma->vm_mm, addr, ptep, &pgsize);

	clear_flush(vma->vm_mm, addr, ptep, pgsize, ncontig);

	return get_clear_flush(vma->vm_mm, addr, ptep, pgsize, ncontig);

}



static int __init hugetlbpage_init(void)

arch/ia64/include/asm/hugetlb.h

+3 −2
Original line number Diff line number Diff line
@@ -23,9 +23,10 @@ static inline int is_hugepage_only_range(struct mm_struct *mm, 
#define is_hugepage_only_range is_hugepage_only_range



#define __HAVE_ARCH_HUGE_PTEP_CLEAR_FLUSH

static inline void huge_ptep_clear_flush(struct vm_area_struct *vma,

static inline pte_t huge_ptep_clear_flush(struct vm_area_struct *vma,

					  unsigned long addr, pte_t *ptep)

{

	return *ptep;

}



#include <asm-generic/hugetlb.h>

arch/mips/include/asm/hugetlb.h

+6 −3
Original line number Diff line number Diff line
@@ -43,16 +43,19 @@ static inline pte_t huge_ptep_get_and_clear(struct mm_struct *mm, 
}



#define __HAVE_ARCH_HUGE_PTEP_CLEAR_FLUSH

static inline void huge_ptep_clear_flush(struct vm_area_struct *vma,

static inline pte_t huge_ptep_clear_flush(struct vm_area_struct *vma,

					  unsigned long addr, pte_t *ptep)

{

	pte_t pte;



	/*

	 * clear the huge pte entry firstly, so that the other smp threads will

	 * not get old pte entry after finishing flush_tlb_page and before

	 * setting new huge pte entry

	 */

	huge_ptep_get_and_clear(vma->vm_mm, addr, ptep);

	pte = huge_ptep_get_and_clear(vma->vm_mm, addr, ptep);

	flush_tlb_page(vma, addr);

	return pte;

}



#define __HAVE_ARCH_HUGE_PTE_NONE

arch/parisc/include/asm/hugetlb.h

+3 −2
Original line number Diff line number Diff line
@@ -28,9 +28,10 @@ static inline int prepare_hugepage_range(struct file *file, 
}



#define __HAVE_ARCH_HUGE_PTEP_CLEAR_FLUSH

static inline void huge_ptep_clear_flush(struct vm_area_struct *vma,

static inline pte_t huge_ptep_clear_flush(struct vm_area_struct *vma,

					  unsigned long addr, pte_t *ptep)

{

	return *ptep;

}



#define __HAVE_ARCH_HUGE_PTEP_SET_WRPROTECT