linux-kernel - [PATCH 10/31] kasan, page_alloc: combine tag_clear_highpage calls in post_alloc

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Message-Id: <48a7a39ddb6fbee4bab6750121d7349eb0364be7.1638308023.git.andreyknvl@google.com>
Date:   Tue, 30 Nov 2021 22:52:40 +0100
From:   andrey.konovalov@...ux.dev
To:     Marco Elver <elver@...gle.com>,
        Alexander Potapenko <glider@...gle.com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Peter Collingbourne <pcc@...gle.com>
Cc:     Andrey Konovalov <andreyknvl@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        kasan-dev@...glegroups.com,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        Will Deacon <will@...nel.org>,
        linux-arm-kernel@...ts.infradead.org,
        Evgenii Stepanov <eugenis@...gle.com>,
        linux-kernel@...r.kernel.org,
        Andrey Konovalov <andreyknvl@...gle.com>
Subject: [PATCH 10/31] kasan, page_alloc: combine tag_clear_highpage calls in post_alloc_hook

From: Andrey Konovalov <andreyknvl@...gle.com>

The patch moves tag_clear_highpage() loops out of the
kasan_has_integrated_init() clause as a code simplification.

This patch does no functional changes.

Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
---
 mm/page_alloc.c | 32 ++++++++++++++++----------------
 1 file changed, 16 insertions(+), 16 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 2a85aeb45ec1..e3e9fefbce43 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2405,30 +2405,30 @@ inline void post_alloc_hook(struct page *page, unsigned int order,
 	 * KASAN unpoisoning and memory initializion code must be
 	 * kept together to avoid discrepancies in behavior.
 	 */
+
+	/*
+	 * If memory tags should be zeroed (which happens only when memory
+	 * should be initialized as well).
+	 */
+	if (init_tags) {
+		int i;
+
+		/* Initialize both memory and tags. */
+		for (i = 0; i != 1 << order; ++i)
+			tag_clear_highpage(page + i);
+
+		/* Note that memory is already initialized by the loop above. */
+		init = false;
+	}
 	if (kasan_has_integrated_init()) {
 		if (gfp_flags & __GFP_SKIP_KASAN_POISON)
 			SetPageSkipKASanPoison(page);
 
-		if (init_tags) {
-			int i;
-
-			for (i = 0; i != 1 << order; ++i)
-				tag_clear_highpage(page + i);
-		} else {
+		if (!init_tags)
 			kasan_unpoison_pages(page, order, init);
-		}
 	} else {
 		kasan_unpoison_pages(page, order, init);
 
-		if (init_tags) {
-			int i;
-
-			for (i = 0; i < 1 << order; i++)
-				tag_clear_highpage(page + i);
-
-			init = false;
-		}
-
 		if (init)
 			kernel_init_free_pages(page, 1 << order);
 	}
-- 
2.25.1