The patch titled
Subject: mm: pgtable: remove unnecessary split ptlock for kernel PMD page
has been added to the -mm mm-unstable branch. Its filename is
mm-pgtable-remove-unnecessary-split-ptlock-for-kernel-pmd-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-remove-unnecessary-split-ptlock-for-kernel-pmd-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: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
Subject: mm: pgtable: remove unnecessary split ptlock for kernel PMD page
Date: Thu, 1 Feb 2024 16:05:41 +0800
For kernel PMD entry, we use init_mm.page_table_lock to protect it, so
there is no need to allocate and initialize the split ptlock for kernel
PMD page.
Link: https://lkml.kernel.org/r/63f0b3d2f9124ae5076963fb5505bd36daba0393.1706774109.git.zhengqi.arch@xxxxxxxxxxxxx
Signed-off-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
Reviewed-by: Muchun Song <muchun.song@xxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/asm-generic/pgalloc.h | 10 ++++++++--
include/linux/mm.h | 21 ++++++++++++++++-----
2 files changed, 24 insertions(+), 7 deletions(-)
--- a/include/asm-generic/pgalloc.h~mm-pgtable-remove-unnecessary-split-ptlock-for-kernel-pmd-page
+++ a/include/asm-generic/pgalloc.h
@@ -139,7 +139,10 @@ static inline pmd_t *pmd_alloc_one(struc
ptdesc = pagetable_alloc(gfp, 0);
if (!ptdesc)
return NULL;
- if (!pagetable_pmd_ctor(ptdesc)) {
+
+ if (mm == &init_mm) {
+ __pagetable_pmd_ctor(ptdesc);
+ } else if (!pagetable_pmd_ctor(ptdesc)) {
pagetable_free(ptdesc);
return NULL;
}
@@ -153,7 +156,10 @@ static inline void pmd_free(struct mm_st
struct ptdesc *ptdesc = virt_to_ptdesc(pmd);
BUG_ON((unsigned long)pmd & (PAGE_SIZE-1));
- pagetable_pmd_dtor(ptdesc);
+ if (mm == &init_mm)
+ __pagetable_pmd_dtor(ptdesc);
+ else
+ pagetable_pmd_dtor(ptdesc);
pagetable_free(ptdesc);
}
#endif
--- a/include/linux/mm.h~mm-pgtable-remove-unnecessary-split-ptlock-for-kernel-pmd-page
+++ a/include/linux/mm.h
@@ -3048,26 +3048,37 @@ static inline spinlock_t *pmd_lock(struc
return ptl;
}
-static inline bool pagetable_pmd_ctor(struct ptdesc *ptdesc)
+static inline void __pagetable_pmd_ctor(struct ptdesc *ptdesc)
{
struct folio *folio = ptdesc_folio(ptdesc);
- if (!pmd_ptlock_init(ptdesc))
- return false;
__folio_set_pgtable(folio);
lruvec_stat_add_folio(folio, NR_PAGETABLE);
+}
+
+static inline bool pagetable_pmd_ctor(struct ptdesc *ptdesc)
+{
+ if (!pmd_ptlock_init(ptdesc))
+ return false;
+
+ __pagetable_pmd_ctor(ptdesc);
return true;
}
-static inline void pagetable_pmd_dtor(struct ptdesc *ptdesc)
+static inline void __pagetable_pmd_dtor(struct ptdesc *ptdesc)
{
struct folio *folio = ptdesc_folio(ptdesc);
- pmd_ptlock_free(ptdesc);
__folio_clear_pgtable(folio);
lruvec_stat_sub_folio(folio, NR_PAGETABLE);
}
+static inline void pagetable_pmd_dtor(struct ptdesc *ptdesc)
+{
+ pmd_ptlock_free(ptdesc);
+ __pagetable_pmd_dtor(ptdesc);
+}
+
/*
* No scalability reason to split PUD locks yet, but follow the same pattern
* as the PMD locks to make it easier if we decide to. The VM should not be
_
Patches currently in -mm which might be from zhengqi.arch@xxxxxxxxxxxxx are
mm-pgtable-add-missing-flag-and-statistics-for-kernel-pte-page.patch
mm-pgtable-remove-unnecessary-split-ptlock-for-kernel-pmd-page.patch
