[PATCH] mm, vmalloc: properly track vmalloc users

[Michal Hocko]

__vmalloc_node_flags used to be static inline but this has changed by
"mm: introduce kv[mz]alloc helpers" because kvmalloc_node needs to use
it as well and the code is outside of the vmalloc proper. I haven't
realized that changing this will lead to a subtle bug though. The
function is responsible to track the caller as well. This caller is
then printed by /proc/vmallocinfo. If __vmalloc_node_flags is not inline
then we would get only direct users of __vmalloc_node_flags as callers
(e.g. v[mz]alloc) which reduces usefulness of this debugging feature
considerably. It simply doesn't help to see that the given range belongs
to vmalloc as a caller:
0xffffc90002c79000-0xffffc90002c7d000   16384 vmalloc+0x16/0x18 pages=3 vmalloc N0=3
0xffffc90002c81000-0xffffc90002c85000   16384 vmalloc+0x16/0x18 pages=3 vmalloc N1=3
0xffffc90002c8d000-0xffffc90002c91000   16384 vmalloc+0x16/0x18 pages=3 vmalloc N1=3
0xffffc90002c95000-0xffffc90002c99000   16384 vmalloc+0x16/0x18 pages=3 vmalloc N1=3

We really want to catch the _caller_ of the vmalloc function. Fix this
issue by making __vmalloc_node_flags static inline again and export
__vmalloc_node_flags_caller for kvmalloc_node().

Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
---
 include/linux/vmalloc.h | 16 +++++++++++++++-
 mm/util.c               |  3 ++-
 mm/vmalloc.c            |  8 +++++++-
 3 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
index 46991ad3ddd5..4a0fabeb1e92 100644
--- a/include/linux/vmalloc.h
+++ b/include/linux/vmalloc.h
@@ -80,7 +80,21 @@ extern void *__vmalloc_node_range(unsigned long size, unsigned long align,
 			unsigned long start, unsigned long end, gfp_t gfp_mask,
 			pgprot_t prot, unsigned long vm_flags, int node,
 			const void *caller);
-extern void *__vmalloc_node_flags(unsigned long size, int node, gfp_t flags);
+#ifndef CONFIG_MMU
+extern void *__vmalloc_node_flags_caller(unsigned long size, int node, gfp_t flags);
+static inline void *__vmalloc_node_flags_caller(unsigned long size, int node, gfp_t flags, void* caller)
+{
+	return __vmalloc_node_flags(size, node, flags);
+}
+#else
+/*
+ * We really want to have this inlined due to caller tracking. This
+ * function is used by the highlevel vmalloc apis and so we want to track
+ * their callers and inlining will achieve that.
+ */
+extern void *__vmalloc_node_flags_caller(unsigned long size,
+					int node, gfp_t flags, void* caller);
+#endif
 
 extern void vfree(const void *addr);
 extern void vfree_atomic(const void *addr);
diff --git a/mm/util.c b/mm/util.c
index 3022051da938..c35e5870921d 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -380,7 +380,8 @@ void *kvmalloc_node(size_t size, gfp_t flags, int node)
 	if (ret || size <= PAGE_SIZE)
 		return ret;
 
-	return __vmalloc_node_flags(size, node, flags);
+	return __vmalloc_node_flags_caller(size, node, flags,
+			__builtin_return_address(0));
 }
 EXPORT_SYMBOL(kvmalloc_node);
 
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 65912eb93a2c..1a97d4a31406 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1809,13 +1809,19 @@ void *__vmalloc(unsigned long size, gfp_t gfp_mask, pgprot_t prot)
 }
 EXPORT_SYMBOL(__vmalloc);
 
-void *__vmalloc_node_flags(unsigned long size,
+static inline void *__vmalloc_node_flags(unsigned long size,
 					int node, gfp_t flags)
 {
 	return __vmalloc_node(size, 1, flags, PAGE_KERNEL,
 					node, __builtin_return_address(0));
 }
 
+
+void *__vmalloc_node_flags_caller(unsigned long size, int node, gfp_t flags, void *caller)
+{
+	return __vmalloc_node(size, 1, flags, PAGE_KERNEL, node, caller);
+}
+
 /**
  *	vmalloc  -  allocate virtually contiguous memory
  *	@size:		allocation size
-- 
2.11.0

-- 
Michal Hocko
SUSE Labs