linux-hardening - [RFC PATCH 05/14] mm/slub: create folio_set/clear

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Date:   Fri, 15 Sep 2023 10:59:24 +0000
From:   Matteo Rizzo <matteorizzo@...gle.com>
To:     cl@...ux.com, penberg@...nel.org, rientjes@...gle.com,
        iamjoonsoo.kim@....com, akpm@...ux-foundation.org, vbabka@...e.cz,
        roman.gushchin@...ux.dev, 42.hyeyoo@...il.com,
        keescook@...omium.org, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-mm@...ck.org,
        linux-hardening@...r.kernel.org, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
        x86@...nel.org, hpa@...or.com, corbet@....net, luto@...nel.org,
        peterz@...radead.org
Cc:     jannh@...gle.com, matteorizzo@...gle.com, evn@...gle.com,
        poprdi@...gle.com, jordyzomer@...gle.com
Subject: [RFC PATCH 05/14] mm/slub: create folio_set/clear_slab helpers

From: Jann Horn <jannh@...gle.com>

This is refactoring in preparation for SLAB_VIRTUAL. Extract this code
to separate functions so that it's not duplicated in the code that
allocates and frees page with SLAB_VIRTUAL enabled.

Signed-off-by: Jann Horn <jannh@...gle.com>
Co-developed-by: Matteo Rizzo <matteorizzo@...gle.com>
Signed-off-by: Matteo Rizzo <matteorizzo@...gle.com>
---
 mm/slub.c | 32 ++++++++++++++++++++++----------
 1 file changed, 22 insertions(+), 10 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index ad33d9e1601d..9b87afade125 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1849,6 +1849,26 @@ static void *setup_object(struct kmem_cache *s, void *object)
 /*
  * Slab allocation and freeing
  */
+
+static void folio_set_slab(struct folio *folio, struct slab *slab)
+{
+	__folio_set_slab(folio);
+	/* Make the flag visible before any changes to folio->mapping */
+	smp_wmb();
+
+	if (folio_is_pfmemalloc(folio))
+		slab_set_pfmemalloc(slab);
+}
+
+static void folio_clear_slab(struct folio *folio, struct slab *slab)
+{
+	__slab_clear_pfmemalloc(slab);
+	folio->mapping = NULL;
+	/* Make the mapping reset visible before clearing the flag */
+	smp_wmb();
+	__folio_clear_slab(folio);
+}
+
 static inline struct slab *alloc_slab_page(gfp_t flags, int node,
 		struct kmem_cache_order_objects oo)
 {
@@ -1865,11 +1885,7 @@ static inline struct slab *alloc_slab_page(gfp_t flags, int node,
 		return NULL;
 
 	slab = folio_slab(folio);
-	__folio_set_slab(folio);
-	/* Make the flag visible before any changes to folio->mapping */
-	smp_wmb();
-	if (folio_is_pfmemalloc(folio))
-		slab_set_pfmemalloc(slab);
+	folio_set_slab(folio, slab);
 
 	return slab;
 }
@@ -2067,11 +2083,7 @@ static void __free_slab(struct kmem_cache *s, struct slab *slab)
 	int order = folio_order(folio);
 	int pages = 1 << order;
 
-	__slab_clear_pfmemalloc(slab);
-	folio->mapping = NULL;
-	/* Make the mapping reset visible before clearing the flag */
-	smp_wmb();
-	__folio_clear_slab(folio);
+	folio_clear_slab(folio, slab);
 	mm_account_reclaimed_pages(pages);
 	unaccount_slab(slab, order, s);
 	__free_pages(&folio->page, order);
-- 
2.42.0.459.ge4e396fd5e-goog