diff mbox series

[066/146] mm: ptep_clear() page table helper

Message ID 20220114220633.tueCIXFno%akpm@linux-foundation.org (mailing list archive)
State New
Headers show
Series [001/146] kthread: add the helper function kthread_run_on_cpu() | expand

Commit Message

Andrew Morton Jan. 14, 2022, 10:06 p.m. UTC 
From: Pasha Tatashin <pasha.tatashin@soleen.com>
Subject: mm: ptep_clear() page table helper

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.

Link: https://lkml.kernel.org/r/20211221154650.1047963-3-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Frederic Weisbecker <frederic@kernel.org>
Cc: Greg Thelen <gthelen@google.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Slaby <jirislaby@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kees Cook <keescook@chromium.org>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Paul Turner <pjt@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sami Tolvanen <samitolvanen@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Wei Xu <weixugc@google.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 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 mbox series

Patch

--- a/Documentation/vm/arch_pgtable_helpers.rst~mm-ptep_clear-page-table-helper
+++ a/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                          |
 +---------------------------+--------------------------------------------------+
--- a/include/linux/pgtable.h~mm-ptep_clear-page-table-helper
+++ a/include/linux/pgtable.h
@@ -258,6 +258,14 @@  static inline int pmdp_clear_flush_young
 #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,
--- a/mm/debug_vm_pgtable.c~mm-ptep_clear-page-table-helper
+++ a/mm/debug_vm_pgtable.c
@@ -652,7 +652,7 @@  static void __init pte_clear_tests(struc
 	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));
 }
--- a/mm/khugepaged.c~mm-ptep_clear-page-table-helper
+++ a/mm/khugepaged.c
@@ -756,11 +756,7 @@  static void __collapse_huge_page_copy(pt
 				 * 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(pt
 			 * 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);