From: Prakash Gupta <guptap@codeaurora.org>
Date: Wed, 13 Sep 2017 16:28:35 -0700
Subject: mm, page_owner: skip unnecessary stack_trace entries
Git-commit: 5f48f0bd4e368425db4424b9afd1bd251d32367a
Patch-mainline: v4.14-rc1
References: VM Functionality, bsc#1063512

The page_owner stacktrace always begin as follows:

  [<ffffff987bfd48f4>] save_stack+0x40/0xc8
  [<ffffff987bfd4da8>] __set_page_owner+0x3c/0x6c

These two entries do not provide any useful information and limits the
available stacktrace depth.  The page_owner stacktrace was skipping
caller function from stack entries but this was missed with commit
f2ca0b557107 ("mm/page_owner: use stackdepot to store stacktrace")

Example page_owner entry after the patch:

  Page allocated via order 0, mask 0x8(ffffff80085fb714)
  PFN 654411 type Movable Block 639 type CMA Flags 0x0(ffffffbe5c7f12c0)
  [<ffffff9b64989c14>] post_alloc_hook+0x70/0x80
  ...
  [<ffffff9b651216e8>] msm_comm_try_state+0x5f8/0x14f4
  [<ffffff9b6512486c>] msm_vidc_open+0x5e4/0x7d0
  [<ffffff9b65113674>] msm_v4l2_open+0xa8/0x224

Link: http://lkml.kernel.org/r/1504078343-28754-2-git-send-email-guptap@codeaurora.org
Fixes: f2ca0b557107 ("mm/page_owner: use stackdepot to store stacktrace")
Signed-off-by: Prakash Gupta <guptap@codeaurora.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 mm/page_owner.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -139,7 +139,7 @@ static noinline depot_stack_handle_t sav
 		.nr_entries = 0,
 		.entries = entries,
 		.max_entries = PAGE_OWNER_STACK_DEPTH,
-		.skip = 0
+		.skip = 2
 	};
 	depot_stack_handle_t handle;