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From:   Muchun Song <songmuchun@bytedance.com>
To:     glider@google.com, elver@google.com, dvyukov@google.com,
        akpm@linux-foundation.org, jannh@google.com, sjpark@amazon.de,
        muchun.song@linux.dev
Cc:     kasan-dev@googlegroups.com, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org,
        Muchun Song <songmuchun@bytedance.com>
Subject: [PATCH 1/6] mm: kfence: simplify kfence pool initialization
Date:   Tue, 28 Mar 2023 17:58:02 +0800
Message-Id: <20230328095807.7014-2-songmuchun@bytedance.com>
In-Reply-To: <20230328095807.7014-1-songmuchun@bytedance.com>
References: <20230328095807.7014-1-songmuchun@bytedance.com>
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There are three similar loops to initialize kfence pool, we could merge
all of them into one loop to simplify the code and make code more
efficient.

Signed-off-by: Muchun Song <songmuchun@bytedance.com>
---
 mm/kfence/core.c | 47 ++++++-----------------------------------------
 1 file changed, 6 insertions(+), 41 deletions(-)

diff --git a/mm/kfence/core.c b/mm/kfence/core.c
index 7d01a2c76e80..de62a84d4830 100644
--- a/mm/kfence/core.c
+++ b/mm/kfence/core.c
@@ -539,35 +539,10 @@ static void rcu_guarded_free(struct rcu_head *h)
 static unsigned long kfence_init_pool(void)
 {
 	unsigned long addr = (unsigned long)__kfence_pool;
-	struct page *pages;
 	int i;
 
 	if (!arch_kfence_init_pool())
 		return addr;
-
-	pages = virt_to_page(__kfence_pool);
-
-	/*
-	 * Set up object pages: they must have PG_slab set, to avoid freeing
-	 * these as real pages.
-	 *
-	 * We also want to avoid inserting kfence_free() in the kfree()
-	 * fast-path in SLUB, and therefore need to ensure kfree() correctly
-	 * enters __slab_free() slow-path.
-	 */
-	for (i = 0; i < KFENCE_POOL_SIZE / PAGE_SIZE; i++) {
-		struct slab *slab = page_slab(nth_page(pages, i));
-
-		if (!i || (i % 2))
-			continue;
-
-		__folio_set_slab(slab_folio(slab));
-#ifdef CONFIG_MEMCG
-		slab->memcg_data = (unsigned long)&kfence_metadata[i / 2 - 1].objcg |
-				   MEMCG_DATA_OBJCGS;
-#endif
-	}
-
 	/*
 	 * Protect the first 2 pages. The first page is mostly unnecessary, and
 	 * merely serves as an extended guard page. However, adding one
@@ -581,8 +556,9 @@ static unsigned long kfence_init_pool(void)
 		addr += PAGE_SIZE;
 	}
 
-	for (i = 0; i < CONFIG_KFENCE_NUM_OBJECTS; i++) {
+	for (i = 0; i < CONFIG_KFENCE_NUM_OBJECTS; i++, addr += 2 * PAGE_SIZE) {
 		struct kfence_metadata *meta = &kfence_metadata[i];
+		struct slab *slab = page_slab(virt_to_page(addr));
 
 		/* Initialize metadata. */
 		INIT_LIST_HEAD(&meta->list);
@@ -593,26 +569,15 @@ static unsigned long kfence_init_pool(void)
 
 		/* Protect the right redzone. */
 		if (unlikely(!kfence_protect(addr + PAGE_SIZE)))
-			goto reset_slab;
-
-		addr += 2 * PAGE_SIZE;
-	}
-
-	return 0;
-
-reset_slab:
-	for (i = 0; i < KFENCE_POOL_SIZE / PAGE_SIZE; i++) {
-		struct slab *slab = page_slab(nth_page(pages, i));
+			return addr;
 
-		if (!i || (i % 2))
-			continue;
+		__folio_set_slab(slab_folio(slab));
 #ifdef CONFIG_MEMCG
-		slab->memcg_data = 0;
+		slab->memcg_data = (unsigned long)&meta->objcg | MEMCG_DATA_OBJCGS;
 #endif
-		__folio_clear_slab(slab_folio(slab));
 	}
 
-	return addr;
+	return 0;
 }
 
 static bool __init kfence_init_pool_early(void)
-- 
2.11.0