The patch titled
Subject: mm/pgtable: add pte_free_defer() for pgtable as page
has been added to the -mm mm-unstable branch. Its filename is
mm-pgtable-add-pte_free_defer-for-pgtable-as-page.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-pgtable-add-pte_free_defer-for-pgtable-as-page.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Hugh Dickins <hughd@xxxxxxxxxx>
Subject: mm/pgtable: add pte_free_defer() for pgtable as page
Date: Tue, 11 Jul 2023 21:39:48 -0700 (PDT)
Add the generic pte_free_defer(), to call pte_free() via call_rcu().
pte_free_defer() will be called inside khugepaged's retract_page_tables()
loop, where allocating extra memory cannot be relied upon. This version
suits all those architectures which use an unfragmented page for one page
table (none of whose pte_free()s use the mm arg which was passed to it).
Link: https://lkml.kernel.org/r/78e921b0-b681-a1b0-dc20-44c9efa4ef3c@xxxxxxxxxx
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Alexander Gordeev <agordeev@xxxxxxxxxxxxx>
Cc: Alistair Popple <apopple@xxxxxxxxxx>
Cc: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
Cc: Anshuman Khandual <anshuman.khandual@xxxxxxx>
Cc: Axel Rasmussen <axelrasmussen@xxxxxxxxxx>
Cc: Christian Borntraeger <borntraeger@xxxxxxxxxxxxx>
Cc: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: Gerald Schaefer <gerald.schaefer@xxxxxxxxxxxxx>
Cc: Heiko Carstens <hca@xxxxxxxxxxxxx>
Cc: Huang, Ying <ying.huang@xxxxxxxxx>
Cc: Ira Weiny <ira.weiny@xxxxxxxxx>
Cc: Jann Horn <jannh@xxxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Lorenzo Stoakes <lstoakes@xxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Mike Rapoport (IBM) <rppt@xxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
Cc: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
Cc: Ralph Campbell <rcampbell@xxxxxxxxxx>
Cc: Russell King <linux@xxxxxxxxxxxxxxx>
Cc: SeongJae Park <sj@xxxxxxxxxx>
Cc: Song Liu <song@xxxxxxxxxx>
Cc: Steven Price <steven.price@xxxxxxx>
Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Cc: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx>
Cc: Vishal Moola (Oracle) <vishal.moola@xxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Yang Shi <shy828301@xxxxxxxxx>
Cc: Yu Zhao <yuzhao@xxxxxxxxxx>
Cc: Zack Rusin <zackr@xxxxxxxxxx>
Cc: Zi Yan <ziy@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/mm_types.h | 4 ++++
include/linux/pgtable.h | 2 ++
mm/pgtable-generic.c | 20 ++++++++++++++++++++
3 files changed, 26 insertions(+)
--- a/include/linux/mm_types.h~mm-pgtable-add-pte_free_defer-for-pgtable-as-page
+++ a/include/linux/mm_types.h
@@ -144,6 +144,10 @@ struct page {
struct { /* Page table pages */
unsigned long _pt_pad_1; /* compound_head */
pgtable_t pmd_huge_pte; /* protected by page->ptl */
+ /*
+ * A PTE page table page might be freed by use of
+ * rcu_head: which overlays those two fields above.
+ */
unsigned long _pt_pad_2; /* mapping */
union {
struct mm_struct *pt_mm; /* x86 pgds only */
--- a/include/linux/pgtable.h~mm-pgtable-add-pte_free_defer-for-pgtable-as-page
+++ a/include/linux/pgtable.h
@@ -112,6 +112,8 @@ static inline void pte_unmap(pte_t *pte)
}
#endif
+void pte_free_defer(struct mm_struct *mm, pgtable_t pgtable);
+
/* Find an entry in the second-level page table.. */
#ifndef pmd_offset
static inline pmd_t *pmd_offset(pud_t *pud, unsigned long address)
--- a/mm/pgtable-generic.c~mm-pgtable-add-pte_free_defer-for-pgtable-as-page
+++ a/mm/pgtable-generic.c
@@ -13,6 +13,7 @@
#include <linux/swap.h>
#include <linux/swapops.h>
#include <linux/mm_inline.h>
+#include <asm/pgalloc.h>
#include <asm/tlb.h>
/*
@@ -230,6 +231,25 @@ pmd_t pmdp_collapse_flush(struct vm_area
return pmd;
}
#endif
+
+/* arch define pte_free_defer in asm/pgalloc.h for its own implementation */
+#ifndef pte_free_defer
+static void pte_free_now(struct rcu_head *head)
+{
+ struct page *page;
+
+ page = container_of(head, struct page, rcu_head);
+ pte_free(NULL /* mm not passed and not used */, (pgtable_t)page);
+}
+
+void pte_free_defer(struct mm_struct *mm, pgtable_t pgtable)
+{
+ struct page *page;
+
+ page = pgtable;
+ call_rcu(&page->rcu_head, pte_free_now);
+}
+#endif /* pte_free_defer */
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
#if defined(CONFIG_GUP_GET_PXX_LOW_HIGH) && \
_
Patches currently in -mm which might be from hughd@xxxxxxxxxx are
mm-userfaultfd-add-new-uffdio_poison-ioctl-fix.patch
mm-pgtable-add-rcu_read_lock-and-rcu_read_unlocks.patch
mm-pgtable-add-pae-safety-to-__pte_offset_map.patch
arm-adjust_pte-use-pte_offset_map_nolock.patch
powerpc-assert_pte_locked-use-pte_offset_map_nolock.patch
powerpc-add-pte_free_defer-for-pgtables-sharing-page.patch
sparc-add-pte_free_defer-for-pte_t-pgtable_t.patch
s390-add-pte_free_defer-for-pgtables-sharing-page.patch
mm-pgtable-add-pte_free_defer-for-pgtable-as-page.patch
mm-khugepaged-retract_page_tables-without-mmap-or-vma-lock.patch
mm-khugepaged-collapse_pte_mapped_thp-with-mmap_read_lock.patch
mm-khugepaged-delete-khugepaged_collapse_pte_mapped_thps.patch
mm-delete-mmap_write_trylock-and-vma_try_start_write.patch
mm-pgtable-notes-on-pte_offset_map.patch
