Patch "mm: kmemleak_alloc_percpu() should follow the gfp from per_alloc()" has been added to the 4.1-stable tree

This is a note to let you know that I've just added the patch titled

mm: kmemleak_alloc_percpu() should follow the gfp from per_alloc()

to the 4.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
mm-kmemleak_alloc_percpu-should-follow-the-gfp-from-per_alloc.patch
and it can be found in the queue-4.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Larry Finger <[email protected]>
Date: Wed, 24 Jun 2015 16:58:51 -0700
Subject: mm: kmemleak_alloc_percpu() should follow the gfp from per_alloc()

From: Larry Finger <[email protected]>

commit 8a8c35fadfaf55629a37ef1a8ead1b8fb32581d2 upstream.

Beginning at commit d52d3997f843 ("ipv6: Create percpu rt6_info"), the following INFO splat is logged:

===============================
[ INFO: suspicious RCU usage. ]
4.1.0-rc7-next-20150612 #1 Not tainted
-------------------------------
kernel/sched/core.c:7318 Illegal context switch in RCU-bh read-side critical section! other info that might help us debug this:
rcu_scheduler_active = 1, debug_locks = 0
3 locks held by systemd/1:

   #0:  (rtnl_mutex){+.+.+.}, at: [<ffffffff815f0c8f>] rtnetlink_rcv+0x1f/0x40
   #1:  (rcu_read_lock_bh){......}, at: [<ffffffff816a34e2>] ipv6_add_addr+0x62/0x540
   #2:  (addrconf_hash_lock){+...+.}, at: [<ffffffff816a3604>] ipv6_add_addr+0x184/0x540
  stack backtrace:
  CPU: 0 PID: 1 Comm: systemd Not tainted 4.1.0-rc7-next-20150612 #1
  Hardware name: TOSHIBA TECRA A50-A/TECRA A50-A, BIOS Version 4.20   04/17/2014
  Call Trace:
    dump_stack+0x4c/0x6e
    lockdep_rcu_suspicious+0xe7/0x120
    ___might_sleep+0x1d5/0x1f0
    __might_sleep+0x4d/0x90
    kmem_cache_alloc+0x47/0x250
    create_object+0x39/0x2e0
    kmemleak_alloc_percpu+0x61/0xe0
    pcpu_alloc+0x370/0x630

Additional backtrace lines are truncated. In addition, the above splat is followed by several "BUG: sleeping function called from invalid context at mm/slub.c:1268" outputs. As suggested by Martin KaFai Lau, these are the clue to the fix. Routine kmemleak_alloc_percpu() always uses GFP_KERNEL for its allocations, whereas it should follow the gfp from its callers.

---
 include/linux/kmemleak.h |    6 ++++--
 mm/kmemleak.c            |    9 +++++----
 mm/percpu.c              |    2 +-
 3 files changed, 10 insertions(+), 7 deletions(-)

@@ -28,7 +28,8 @@
 extern void kmemleak_init(void) __ref;
 extern void kmemleak_alloc(const void *ptr, size_t size, int min_count,
 			   gfp_t gfp) __ref;
-extern void kmemleak_alloc_percpu(const void __percpu *ptr, size_t size) __ref;
+extern void kmemleak_alloc_percpu(const void __percpu *ptr, size_t size,
+				  gfp_t gfp) __ref;
 extern void kmemleak_free(const void *ptr) __ref;
 extern void kmemleak_free_part(const void *ptr, size_t size) __ref;
 extern void kmemleak_free_percpu(const void __percpu *ptr) __ref;

@@ -71,7 +72,8 @@ static inline void kmemleak_alloc_recurs
 					    gfp_t gfp)
 {
 }
-static inline void kmemleak_alloc_percpu(const void __percpu *ptr, size_t size)
+static inline void kmemleak_alloc_percpu(const void __percpu *ptr, size_t size,
+					 gfp_t gfp)
 {
 }
 static inline void kmemleak_free(const void *ptr)

@@ -909,12 +909,13 @@ EXPORT_SYMBOL_GPL(kmemleak_alloc);
  * kmemleak_alloc_percpu - register a newly allocated __percpu object
  * @ptr:	__percpu pointer to beginning of the object
  * @size:	size of the object
+ * @gfp:	flags used for kmemleak internal memory allocations
  *
  * This function is called from the kernel percpu allocator when a new object
- * (memory block) is allocated (alloc_percpu). It assumes GFP_KERNEL
- * allocation.
+ * (memory block) is allocated (alloc_percpu).
  */
-void __ref kmemleak_alloc_percpu(const void __percpu *ptr, size_t size)
+void __ref kmemleak_alloc_percpu(const void __percpu *ptr, size_t size,
+				 gfp_t gfp)
 {
 	unsigned int cpu;
 

@@ -927,7 +928,7 @@ void __ref kmemleak_alloc_percpu(const v
 	if (kmemleak_enabled && ptr && !IS_ERR(ptr))
 		for_each_possible_cpu(cpu)
 			create_object((unsigned long)per_cpu_ptr(ptr, cpu),
-				      size, 0, GFP_KERNEL);
+				      size, 0, gfp);
 	else if (kmemleak_early_log)
 		log_early(KMEMLEAK_ALLOC_PERCPU, ptr, size, 0);
 }

@@ -1030,7 +1030,7 @@ area_found:
 		memset((void *)pcpu_chunk_addr(chunk, cpu, 0) + off, 0, size);
 
 	ptr = __addr_to_pcpu_ptr(chunk->base_addr + off);
-	kmemleak_alloc_percpu(ptr, size);
+	kmemleak_alloc_percpu(ptr, size, gfp);
 	return ptr;
 
 fail_unlock:

Patches currently in stable-queue which might be from [email protected] are

queue-4.1/mm-kmemleak_alloc_percpu-should-follow-the-gfp-from-per_alloc.patch