[RFC PATCH 02/14] mm/slub: add is_slab_addr/is_slab_page helpers

[Matteo Rizzo]

From: Jann Horn <jannh@xxxxxxxxxx>

This is refactoring in preparation for adding two different
implementations (for SLAB_VIRTUAL enabled and disabled).

virt_to_folio(x) expands to _compound_head(virt_to_page(x)) and
virt_to_head_page(x) also expands to _compound_head(virt_to_page(x))

so PageSlab(virt_to_head_page(res)) should be equivalent to
is_slab_addr(res).

Signed-off-by: Jann Horn <jannh@xxxxxxxxxx>
Co-developed-by: Matteo Rizzo <matteorizzo@xxxxxxxxxx>
Signed-off-by: Matteo Rizzo <matteorizzo@xxxxxxxxxx>
---
 include/linux/slab.h | 1 +
 kernel/resource.c    | 2 +-
 mm/slab.h            | 9 +++++++++
 mm/slab_common.c     | 5 ++---
 mm/slub.c            | 6 +++---
 5 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/include/linux/slab.h b/include/linux/slab.h
index 8228d1276a2f..a2d82010d269 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -793,4 +793,5 @@ int slab_dead_cpu(unsigned int cpu);
 #define slab_dead_cpu		NULL
 #endif
 
+#define is_slab_addr(addr) folio_test_slab(virt_to_folio(addr))
 #endif	/* _LINUX_SLAB_H */
diff --git a/kernel/resource.c b/kernel/resource.c
index b1763b2fd7ef..c829e5f97292 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -158,7 +158,7 @@ static void free_resource(struct resource *res)
 	 * buddy and trying to be smart and reusing them eventually in
 	 * alloc_resource() overcomplicates resource handling.
 	 */
-	if (res && PageSlab(virt_to_head_page(res)))
+	if (res && is_slab_addr(res))
 		kfree(res);
 }
 
diff --git a/mm/slab.h b/mm/slab.h
index 799a315695c6..25e41dd6087e 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -169,6 +169,15 @@ static_assert(IS_ALIGNED(offsetof(struct slab, freelist), sizeof(freelist_aba_t)
  */
 #define slab_page(s) folio_page(slab_folio(s), 0)
 
+/**
+ * is_slab_page - Checks if a page is really a slab page
+ * @s: The slab
+ *
+ * Checks if s points to a slab page.
+ *
+ * Return: true if s points to a slab and false otherwise.
+ */
+#define is_slab_page(s) folio_test_slab(slab_folio(s))
 /*
  * If network-based swap is enabled, sl*b must keep track of whether pages
  * were allocated from pfmemalloc reserves.
diff --git a/mm/slab_common.c b/mm/slab_common.c
index e99e821065c3..79102d24f099 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -1063,7 +1063,7 @@ void kfree(const void *object)
 		return;
 
 	folio = virt_to_folio(object);
-	if (unlikely(!folio_test_slab(folio))) {
+	if (unlikely(!is_slab_addr(object))) {
 		free_large_kmalloc(folio, (void *)object);
 		return;
 	}
@@ -1094,8 +1094,7 @@ size_t __ksize(const void *object)
 		return 0;
 
 	folio = virt_to_folio(object);
-
-	if (unlikely(!folio_test_slab(folio))) {
+	if (unlikely(!is_slab_addr(object))) {
 		if (WARN_ON(folio_size(folio) <= KMALLOC_MAX_CACHE_SIZE))
 			return 0;
 		if (WARN_ON(object != folio_address(folio)))
diff --git a/mm/slub.c b/mm/slub.c
index a7dae207c2d2..b69916ab7aa8 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1259,7 +1259,7 @@ static int check_slab(struct kmem_cache *s, struct slab *slab)
 {
 	int maxobj;
 
-	if (!folio_test_slab(slab_folio(slab))) {
+	if (!is_slab_page(slab)) {
 		slab_err(s, slab, "Not a valid slab page");
 		return 0;
 	}
@@ -1454,7 +1454,7 @@ static noinline bool alloc_debug_processing(struct kmem_cache *s,
 	return true;
 
 bad:
-	if (folio_test_slab(slab_folio(slab))) {
+	if (is_slab_page(slab)) {
 		/*
 		 * If this is a slab page then lets do the best we can
 		 * to avoid issues in the future. Marking all objects
@@ -1484,7 +1484,7 @@ static inline int free_consistency_checks(struct kmem_cache *s,
 		return 0;
 
 	if (unlikely(s != slab->slab_cache)) {
-		if (!folio_test_slab(slab_folio(slab))) {
+		if (!is_slab_page(slab)) {
 			slab_err(s, slab, "Attempt to free object(0x%p) outside of slab",
 				 object);
 		} else if (!slab->slab_cache) {
-- 
2.42.0.459.ge4e396fd5e-goog