Commit 08d5b29e authored by Pasha Tatashin's avatar Pasha Tatashin Committed by Linus Torvalds
Browse files

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: default avatarPasha 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 1eba86c0

Documentation/vm/arch_pgtable_helpers.rst

+4 −2
Original line number Diff line number Diff line
@@ -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                          |

+---------------------------+--------------------------------------------------+

include/linux/pgtable.h

+8 −0
Original line number Diff line number Diff line
@@ -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,

mm/debug_vm_pgtable.c

+1 −1
Original line number Diff line number Diff line
@@ -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));

}

mm/khugepaged.c

+2 −10
Original line number Diff line number Diff line
@@ -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);