[v4,1/2] mm: Remove kmem_valid_obj()

Commit Message

Leizhen (ThunderTown) Aug. 2, 2023, 1:09 p.m. UTC

From: Zhen Lei <[e-mail]>

Function kmem_dump_obj() will splat if passed a pointer to a non-slab
object. So no one will call it directly. It is always necessary to call
kmem_valid_obj() first to determine whether the passed pointer to a
valid slab object. Then merging kmem_valid_obj() into kmem_dump_obj()
will make the code more concise. So convert kmem_dump_obj() to work the
same way as vmalloc_dump_obj(). After this, no one calls kmem_valid_obj()
anymore, and it can be safely removed.

Suggested-by: Matthew Wilcox <[e-mail]>
Signed-off-by: Zhen Lei <[e-mail]>
---
 include/linux/slab.h |  5 +++--
 mm/slab_common.c     | 41 +++++++++++------------------------------
 mm/util.c            |  4 +---
 3 files changed, 15 insertions(+), 35 deletions(-)

Comments

Matthew Wilcox (Oracle) Aug. 2, 2023, 1:46 p.m. UTC | #1

On Wed, Aug 02, 2023 at 09:09:17PM +0800, [e-mail] wrote:
> From: Zhen Lei <[e-mail]>
> 
> Function kmem_dump_obj() will splat if passed a pointer to a non-slab
> object. So no one will call it directly. It is always necessary to call
> kmem_valid_obj() first to determine whether the passed pointer to a
> valid slab object. Then merging kmem_valid_obj() into kmem_dump_obj()
> will make the code more concise. So convert kmem_dump_obj() to work the
> same way as vmalloc_dump_obj(). After this, no one calls kmem_valid_obj()
> anymore, and it can be safely removed.
> 
> Suggested-by: Matthew Wilcox <[e-mail]>
> Signed-off-by: Zhen Lei <[e-mail]>

Reviewed-by: Matthew Wilcox (Oracle) <[e-mail]>

Vlastimil Babka Aug. 3, 2023, 9:36 a.m. UTC | #2

On 8/2/23 15:09, [e-mail] wrote:
> From: Zhen Lei <[e-mail]>
> 
> Function kmem_dump_obj() will splat if passed a pointer to a non-slab
> object. So no one will call it directly. It is always necessary to call
> kmem_valid_obj() first to determine whether the passed pointer to a
> valid slab object. Then merging kmem_valid_obj() into kmem_dump_obj()
> will make the code more concise. So convert kmem_dump_obj() to work the
> same way as vmalloc_dump_obj(). After this, no one calls kmem_valid_obj()
> anymore, and it can be safely removed.
> 
> Suggested-by: Matthew Wilcox <[e-mail]>
> Signed-off-by: Zhen Lei <[e-mail]>

Acked-by: Vlastimil Babka <[e-mail]>

No problem if this goes through rcu tree due to patch 2/2.

Patch

diff --git a/include/linux/slab.h b/include/linux/slab.h
index 848c7c82ad5ad0b..d8ed2e810ec4448 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -244,8 +244,9 @@  DEFINE_FREE(kfree, void *, if (_T) kfree(_T))
 size_t ksize(const void *objp);
 
 #ifdef CONFIG_PRINTK
-bool kmem_valid_obj(void *object);
-void kmem_dump_obj(void *object);
+bool kmem_dump_obj(void *object);
+#else
+static inline bool kmem_dump_obj(void *object) { return false; }
 #endif
 
 /*
diff --git a/mm/slab_common.c b/mm/slab_common.c
index d1555ea2981ac51..ee6ed6dd7ba9fa5 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -528,26 +528,6 @@  bool slab_is_available(void)
 }
 
 #ifdef CONFIG_PRINTK
-/**
- * kmem_valid_obj - does the pointer reference a valid slab object?
- * @object: pointer to query.
- *
- * Return: %true if the pointer is to a not-yet-freed object from
- * kmalloc() or kmem_cache_alloc(), either %true or %false if the pointer
- * is to an already-freed object, and %false otherwise.
- */
-bool kmem_valid_obj(void *object)
-{
-	struct folio *folio;
-
-	/* Some arches consider ZERO_SIZE_PTR to be a valid address. */
-	if (object < (void *)PAGE_SIZE || !virt_addr_valid(object))
-		return false;
-	folio = virt_to_folio(object);
-	return folio_test_slab(folio);
-}
-EXPORT_SYMBOL_GPL(kmem_valid_obj);
-
 static void kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct slab *slab)
 {
 	if (__kfence_obj_info(kpp, object, slab))
@@ -566,11 +546,11 @@  static void kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct slab *
  * and, if available, the slab name, return address, and stack trace from
  * the allocation and last free path of that object.
  *
- * This function will splat if passed a pointer to a non-slab object.
- * If you are not sure what type of object you have, you should instead
- * use mem_dump_obj().
+ * Return: %true if the pointer is to a not-yet-freed object from
+ * kmalloc() or kmem_cache_alloc(), either %true or %false if the pointer
+ * is to an already-freed object, and %false otherwise.
  */
-void kmem_dump_obj(void *object)
+bool kmem_dump_obj(void *object)
 {
 	char *cp = IS_ENABLED(CONFIG_MMU) ? "" : "/vmalloc";
 	int i;
@@ -578,13 +558,13 @@  void kmem_dump_obj(void *object)
 	unsigned long ptroffset;
 	struct kmem_obj_info kp = { };
 
-	if (WARN_ON_ONCE(!virt_addr_valid(object)))
-		return;
+	/* Some arches consider ZERO_SIZE_PTR to be a valid address. */
+	if (object < (void *)PAGE_SIZE || !virt_addr_valid(object))
+		return false;
 	slab = virt_to_slab(object);
-	if (WARN_ON_ONCE(!slab)) {
-		pr_cont(" non-slab memory.\n");
-		return;
-	}
+	if (!slab)
+		return false;
+
 	kmem_obj_info(&kp, object, slab);
 	if (kp.kp_slab_cache)
 		pr_cont(" slab%s %s", cp, kp.kp_slab_cache->name);
@@ -621,6 +601,7 @@  void kmem_dump_obj(void *object)
 		pr_info("    %pS\n", kp.kp_free_stack[i]);
 	}
 
+	return true;
 }
 EXPORT_SYMBOL_GPL(kmem_dump_obj);
 #endif
diff --git a/mm/util.c b/mm/util.c
index dd12b9531ac4cad..ddfbb22dc1876d3 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -1063,10 +1063,8 @@  void mem_dump_obj(void *object)
 {
 	const char *type;
 
-	if (kmem_valid_obj(object)) {
-		kmem_dump_obj(object);
+	if (kmem_dump_obj(object))
 		return;
-	}
 
 	if (vmalloc_dump_obj(object))
 		return;