The patch titled
Subject: powerpc: add pte_free_defer() for pgtables sharing page
has been added to the -mm mm-unstable branch. Its filename is
powerpc-add-pte_free_defer-for-pgtables-sharing-page.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/powerpc-add-pte_free_defer-for-pgtables-sharing-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: powerpc: add pte_free_defer() for pgtables sharing page
Date: Tue, 11 Jul 2023 21:35:59 -0700 (PDT)
Add powerpc-specific pte_free_defer(), to free table page 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 precedes
the generic version to avoid build breakage from incompatible pgtable_t.
This is awkward because the struct page contains only one rcu_head, but
that page may be shared between PTE_FRAG_NR pagetables, each wanting to
use the rcu_head at the same time. But powerpc never reuses a fragment
once it has been freed: so mark the page Active in pte_free_defer(),
before calling pte_fragment_free() directly; and there call_rcu() to
pte_free_now() when last fragment is freed and the page is PageActive.
Link: https://lkml.kernel.org/r/6e3ca5f1-334d-4b14-b92d-fc8e99914fcb@xxxxxxxxxx
Suggested-by: Jason Gunthorpe <jgg@xxxxxxxx>
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: 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>
---
arch/powerpc/include/asm/pgalloc.h | 4 +++
arch/powerpc/mm/pgtable-frag.c | 29 ++++++++++++++++++++++++---
2 files changed, 30 insertions(+), 3 deletions(-)
--- a/arch/powerpc/include/asm/pgalloc.h~powerpc-add-pte_free_defer-for-pgtables-sharing-page
+++ a/arch/powerpc/include/asm/pgalloc.h
@@ -45,6 +45,10 @@ static inline void pte_free(struct mm_st
pte_fragment_free((unsigned long *)ptepage, 0);
}
+/* arch use pte_free_defer() implementation in arch/powerpc/mm/pgtable-frag.c */
+#define pte_free_defer pte_free_defer
+void pte_free_defer(struct mm_struct *mm, pgtable_t pgtable);
+
/*
* Functions that deal with pagetables that could be at any level of
* the table need to be passed an "index_size" so they know how to
--- a/arch/powerpc/mm/pgtable-frag.c~powerpc-add-pte_free_defer-for-pgtables-sharing-page
+++ a/arch/powerpc/mm/pgtable-frag.c
@@ -106,6 +106,15 @@ pte_t *pte_fragment_alloc(struct mm_stru
return __alloc_for_ptecache(mm, kernel);
}
+static void pte_free_now(struct rcu_head *head)
+{
+ struct page *page;
+
+ page = container_of(head, struct page, rcu_head);
+ pgtable_pte_page_dtor(page);
+ __free_page(page);
+}
+
void pte_fragment_free(unsigned long *table, int kernel)
{
struct page *page = virt_to_page(table);
@@ -115,8 +124,22 @@ void pte_fragment_free(unsigned long *ta
BUG_ON(atomic_read(&page->pt_frag_refcount) <= 0);
if (atomic_dec_and_test(&page->pt_frag_refcount)) {
- if (!kernel)
- pgtable_pte_page_dtor(page);
- __free_page(page);
+ if (kernel)
+ __free_page(page);
+ else if (TestClearPageActive(page))
+ call_rcu(&page->rcu_head, pte_free_now);
+ else
+ pte_free_now(&page->rcu_head);
}
}
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+void pte_free_defer(struct mm_struct *mm, pgtable_t pgtable)
+{
+ struct page *page;
+
+ page = virt_to_page(pgtable);
+ SetPageActive(page);
+ pte_fragment_free((unsigned long *)pgtable, 0);
+}
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
_
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
