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>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index e991011..9d40dd8 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);