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Date: Wed, 08 Jul 2009 10:42:21 +0100
From: Catalin Marinas <catalin.marinas@....com>
To: Pekka Enberg <penberg@...helsinki.fi>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
Ingo Molnar <mingo@...e.hu>, akpm@...ux-foundation.org
Subject: Re: [RFC PATCH 1/3] kmemleak: Allow partial freeing of memory
blocks
On Wed, 2009-07-08 at 09:40 +0300, Pekka Enberg wrote:
> Looks good to me. I think it would be better to have
> delete_object_full() and delete_object_part(), and extract the common
> code to __delete_object() or something instead of passing the magic zero
> from kmemleak_free().
Yes, it make sense:
kmemleak: Allow partial freeing of memory blocks
From: Catalin Marinas <catalin.marinas@....com>
Functions like free_bootmem() are allowed to free only part of a memory
block. This patch adds support for this via the kmemleak_free_part()
callback which removes the original object and creates one or two
additional objects as a result of the memory block split.
Signed-off-by: Catalin Marinas <catalin.marinas@....com>
Cc: Ingo Molnar <mingo@...e.hu>
Cc: Pekka Enberg <penberg@...helsinki.fi>
---
include/linux/kmemleak.h | 4 ++
mm/kmemleak.c | 95 +++++++++++++++++++++++++++++++++++++++-------
2 files changed, 85 insertions(+), 14 deletions(-)
diff --git a/include/linux/kmemleak.h b/include/linux/kmemleak.h
index 7796aed..6a63807 100644
--- a/include/linux/kmemleak.h
+++ b/include/linux/kmemleak.h
@@ -27,6 +27,7 @@ extern void kmemleak_init(void);
extern void kmemleak_alloc(const void *ptr, size_t size, int min_count,
gfp_t gfp);
extern void kmemleak_free(const void *ptr);
+extern void kmemleak_free_part(const void *ptr, size_t size);
extern void kmemleak_padding(const void *ptr, unsigned long offset,
size_t size);
extern void kmemleak_not_leak(const void *ptr);
@@ -71,6 +72,9 @@ static inline void kmemleak_alloc_recursive(const void *ptr, size_t size,
static inline void kmemleak_free(const void *ptr)
{
}
+static inline void kmemleak_free_part(const void *ptr, size_t size)
+{
+}
static inline void kmemleak_free_recursive(const void *ptr, unsigned long flags)
{
}
diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index 5f7d8ae..7b4647d 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -210,6 +210,7 @@ static DEFINE_MUTEX(scan_mutex);
enum {
KMEMLEAK_ALLOC,
KMEMLEAK_FREE,
+ KMEMLEAK_FREE_PART,
KMEMLEAK_NOT_LEAK,
KMEMLEAK_IGNORE,
KMEMLEAK_SCAN_AREA,
@@ -524,27 +525,17 @@ out:
* Remove the metadata (struct kmemleak_object) for a memory block from the
* object_list and object_tree_root and decrement its use_count.
*/
-static void delete_object(unsigned long ptr)
+static void __delete_object(struct kmemleak_object *object)
{
unsigned long flags;
- struct kmemleak_object *object;
write_lock_irqsave(&kmemleak_lock, flags);
- object = lookup_object(ptr, 0);
- if (!object) {
-#ifdef DEBUG
- kmemleak_warn("Freeing unknown object at 0x%08lx\n",
- ptr);
-#endif
- write_unlock_irqrestore(&kmemleak_lock, flags);
- return;
- }
prio_tree_remove(&object_tree_root, &object->tree_node);
list_del_rcu(&object->object_list);
write_unlock_irqrestore(&kmemleak_lock, flags);
WARN_ON(!(object->flags & OBJECT_ALLOCATED));
- WARN_ON(atomic_read(&object->use_count) < 1);
+ WARN_ON(atomic_read(&object->use_count) < 2);
/*
* Locking here also ensures that the corresponding memory block
@@ -557,6 +548,64 @@ static void delete_object(unsigned long ptr)
}
/*
+ * Look up the metadata (struct kmemleak_object) corresponding to ptr and
+ * delete it.
+ */
+static void delete_object_full(unsigned long ptr)
+{
+ struct kmemleak_object *object;
+
+ object = find_and_get_object(ptr, 0);
+ if (!object) {
+#ifdef DEBUG
+ kmemleak_warn("Freeing unknown object at 0x%08lx\n",
+ ptr);
+#endif
+ return;
+ }
+ __delete_object(object);
+ put_object(object);
+}
+
+/*
+ * Look up the metadata (struct kmemleak_object) corresponding to ptr and
+ * delete it. If the memory block is partially freed, the function may create
+ * additional metadata for the remaining parts of the block.
+ */
+static void delete_object_part(unsigned long ptr, size_t size)
+{
+ struct kmemleak_object *object;
+ unsigned long start, end;
+
+ object = find_and_get_object(ptr, 1);
+ if (!object) {
+#ifdef DEBUG
+ kmemleak_warn("Partially freeing unknown object at 0x%08lx "
+ "(size %zu)\n", ptr, size);
+#endif
+ return;
+ }
+ __delete_object(object);
+
+ /*
+ * Create one or two objects that may result from the memory block
+ * split. Note that partial freeing is only done by free_bootmem() and
+ * this happens before kmemleak_init() is called. The path below is
+ * only executed during early log recording in kmemleak_init(), so
+ * GFP_KERNEL is enough.
+ */
+ start = object->pointer;
+ end = object->pointer + object->size;
+ if (ptr > start)
+ create_object(start, ptr - start, object->min_count,
+ GFP_KERNEL);
+ if (ptr + size < end)
+ create_object(ptr + size, end - ptr - size, object->min_count,
+ GFP_KERNEL);
+
+ put_object(object);
+}
+/*
* Make a object permanently as gray-colored so that it can no longer be
* reported as a leak. This is used in general to mark a false positive.
*/
@@ -720,13 +769,28 @@ void kmemleak_free(const void *ptr)
pr_debug("%s(0x%p)\n", __func__, ptr);
if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
- delete_object((unsigned long)ptr);
+ delete_object_full((unsigned long)ptr);
else if (atomic_read(&kmemleak_early_log))
log_early(KMEMLEAK_FREE, ptr, 0, 0, 0, 0);
}
EXPORT_SYMBOL_GPL(kmemleak_free);
/*
+ * Partial memory freeing function callback. This function is usually called
+ * from bootmem allocator when (part of) a memory block is freed.
+ */
+void kmemleak_free_part(const void *ptr, size_t size)
+{
+ pr_debug("%s(0x%p)\n", __func__, ptr);
+
+ if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
+ delete_object_part((unsigned long)ptr, size);
+ else if (atomic_read(&kmemleak_early_log))
+ log_early(KMEMLEAK_FREE_PART, ptr, size, 0, 0, 0);
+}
+EXPORT_SYMBOL_GPL(kmemleak_free_part);
+
+/*
* Mark an already allocated memory block as a false positive. This will cause
* the block to no longer be reported as leak and always be scanned.
*/
@@ -1345,7 +1409,7 @@ static int kmemleak_cleanup_thread(void *arg)
rcu_read_lock();
list_for_each_entry_rcu(object, &object_list, object_list)
- delete_object(object->pointer);
+ delete_object_full(object->pointer);
rcu_read_unlock();
mutex_unlock(&scan_mutex);
@@ -1440,6 +1504,9 @@ void __init kmemleak_init(void)
case KMEMLEAK_FREE:
kmemleak_free(log->ptr);
break;
+ case KMEMLEAK_FREE_PART:
+ kmemleak_free_part(log->ptr, log->size);
+ break;
case KMEMLEAK_NOT_LEAK:
kmemleak_not_leak(log->ptr);
break;
--
Catalin
--
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