linux-kernel - [PATCH v7 10/16] mm: define clear_pages(), clear_user

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Message-Id: <20250917152418.4077386-11-ankur.a.arora@oracle.com>
Date: Wed, 17 Sep 2025 08:24:12 -0700
From: Ankur Arora <ankur.a.arora@...cle.com>
To: linux-kernel@...r.kernel.org, linux-mm@...ck.org, x86@...nel.org
Cc: akpm@...ux-foundation.org, david@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, hpa@...or.com, mingo@...hat.com,
        mjguzik@...il.com, luto@...nel.org, peterz@...radead.org,
        acme@...nel.org, namhyung@...nel.org, tglx@...utronix.de,
        willy@...radead.org, raghavendra.kt@....com,
        boris.ostrovsky@...cle.com, konrad.wilk@...cle.com,
        ankur.a.arora@...cle.com
Subject: [PATCH v7 10/16] mm: define clear_pages(), clear_user_pages()

Define fallback versions of clear_pages(), clear_user_pages().

In absence of architectural primitives, we just clear pages
sequentially.

Signed-off-by: Ankur Arora <ankur.a.arora@...cle.com>
---
 include/linux/mm.h | 38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 1ae97a0b8ec7..0cde9b01da5e 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -3768,6 +3768,44 @@ static inline void clear_page_guard(struct zone *zone, struct page *page,
 				unsigned int order) {}
 #endif	/* CONFIG_DEBUG_PAGEALLOC */
 
+#ifndef clear_pages
+/**
+ * clear_pages() - clear a page range using a kernel virtual address.
+ * @addr: start address
+ * @npages: number of pages
+ *
+ * Assumes that (@addr, +@...ges) references a kernel region.
+ * Does absolutely no exception handling.
+ */
+static inline void clear_pages(void *addr, unsigned int npages)
+{
+	do {
+		clear_page(addr);
+		addr += PAGE_SIZE;
+	} while (--npages);
+}
+#endif
+
+#ifndef clear_user_pages
+/**
+ * clear_user_pages() - clear a page range mapped by the user.
+ * @addr: kernel mapped address
+ * @vaddr: user mapped address
+ * @pg: start page
+ * @npages: number of pages
+ *
+ * Assumes that the region (@addr, +@...ges) has been validated
+ * already so this does no exception handling.
+ */
+#define clear_user_pages(addr, vaddr, pg, npages)	\
+do {							\
+	clear_user_page(addr, vaddr, pg);		\
+	addr += PAGE_SIZE;				\
+	vaddr += PAGE_SIZE;				\
+	pg++;						\
+} while (--npages)
+#endif
+
 #ifdef __HAVE_ARCH_GATE_AREA
 extern struct vm_area_struct *get_gate_vma(struct mm_struct *mm);
 extern int in_gate_area_no_mm(unsigned long addr);
-- 
2.43.5