lkml.org 
[lkml]   [2021]   [Dec]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v2 2/4] mm: ptep_clear() page table helper
Date
We have ptep_get_and_clear() and ptep_get_and_clear_full() helpers to
clear PTE from user page tables, but there is no variant for simple
clear of a present PTE from user page tables without using a low level
pte_clear() which can be either native or para-virtualised.

Add a new ptep_clear() that can be used in common code to clear PTEs
from page table. We will need this call later in order to add a hook
for page table check.

Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
Documentation/vm/arch_pgtable_helpers.rst | 6 ++++--
include/linux/pgtable.h | 8 ++++++++
mm/debug_vm_pgtable.c | 2 +-
mm/khugepaged.c | 12 ++----------
4 files changed, 15 insertions(+), 13 deletions(-)

diff --git a/Documentation/vm/arch_pgtable_helpers.rst b/Documentation/vm/arch_pgtable_helpers.rst
index 552567d863b8..fbe06ec75370 100644
--- a/Documentation/vm/arch_pgtable_helpers.rst
+++ b/Documentation/vm/arch_pgtable_helpers.rst
@@ -66,9 +66,11 @@ PTE Page Table Helpers
+---------------------------+--------------------------------------------------+
| pte_mknotpresent | Invalidates a mapped PTE |
+---------------------------+--------------------------------------------------+
-| ptep_get_and_clear | Clears a PTE |
+| ptep_clear | Clears a PTE |
+---------------------------+--------------------------------------------------+
-| ptep_get_and_clear_full | Clears a PTE |
+| ptep_get_and_clear | Clears and returns PTE |
++---------------------------+--------------------------------------------------+
+| ptep_get_and_clear_full | Clears and returns PTE (batched PTE unmap) |
+---------------------------+--------------------------------------------------+
| ptep_test_and_clear_young | Clears young from a PTE |
+---------------------------+--------------------------------------------------+
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index e24d2c992b11..bc8713a76e03 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -258,6 +258,14 @@ static inline int pmdp_clear_flush_young(struct vm_area_struct *vma,
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
#endif

+#ifndef __HAVE_ARCH_PTEP_CLEAR
+static inline void ptep_clear(struct mm_struct *mm, unsigned long addr,
+ pte_t *ptep)
+{
+ pte_clear(mm, addr, ptep);
+}
+#endif
+
#ifndef __HAVE_ARCH_PTEP_GET_AND_CLEAR
static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
unsigned long address,
diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
index 228e3954b90c..cd48a34c87a4 100644
--- a/mm/debug_vm_pgtable.c
+++ b/mm/debug_vm_pgtable.c
@@ -652,7 +652,7 @@ static void __init pte_clear_tests(struct pgtable_debug_args *args)
set_pte_at(args->mm, args->vaddr, args->ptep, pte);
flush_dcache_page(page);
barrier();
- pte_clear(args->mm, args->vaddr, args->ptep);
+ ptep_clear(args->mm, args->vaddr, args->ptep);
pte = ptep_get(args->ptep);
WARN_ON(!pte_none(pte));
}
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index dd807261ed9f..c78242d15406 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -756,11 +756,7 @@ static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
* ptl mostly unnecessary.
*/
spin_lock(ptl);
- /*
- * paravirt calls inside pte_clear here are
- * superfluous.
- */
- pte_clear(vma->vm_mm, address, _pte);
+ ptep_clear(vma->vm_mm, address, _pte);
spin_unlock(ptl);
}
} else {
@@ -774,11 +770,7 @@ static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
* inside page_remove_rmap().
*/
spin_lock(ptl);
- /*
- * paravirt calls inside pte_clear here are
- * superfluous.
- */
- pte_clear(vma->vm_mm, address, _pte);
+ ptep_clear(vma->vm_mm, address, _pte);
page_remove_rmap(src_page, false);
spin_unlock(ptl);
free_page_and_swap_cache(src_page);
--
2.34.1.400.ga245620fadb-goog
\
 
 \ /
  Last update: 2021-12-04 19:24    [W:0.051 / U:0.672 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site