- rel 3; v2 version of the patchauto/th/kernel-4.20.3-3

1 files changed, 70 insertions, 110 deletions

diff --git a/kernel-small_fixes.patch b/kernel-small_fixes.patch
index 1961027..c210e45 100644
--- a/kernel-small_fixes.patch
+++ b/kernel-small_fixes.patch
@@ -162,113 +162,73 @@ index 76c92e31afc0..abb5d382f64d 100644
 -- 
 cgit 1.2-0.3.lf.el7
 
-From 48744b6339cf649a69b55997e138c17df1ecc897 Mon Sep 17 00:00:00 2001

-From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>

-Date: Sat, 26 Jan 2019 20:00:51 +0900

-Subject: [PATCH] oom, oom_reaper: do not enqueue same task twice

-

-Arkadiusz reported that enabling memcg's group oom killing causes

-strange memcg statistics where there is no task in a memcg despite

-the number of tasks in that memcg is not 0. It turned out that there

-is a bug in wake_oom_reaper() which allows enqueuing same task twice

-which makes impossible to decrease the number of tasks in that memcg

-due to a refcount leak.

-

-This bug existed since the OOM reaper became invokable from

-task_will_free_mem(current) path in out_of_memory() in Linux 4.7,

-but memcg's group oom killing made it easier to trigger this bug by

-calling wake_oom_reaper() on the same task from one out_of_memory()

-request.

-

-Fix this bug using an approach used by commit 855b018325737f76

-("oom, oom_reaper: disable oom_reaper for oom_kill_allocating_task").

-Since task_will_free_mem(p) == false if p->mm == NULL, we can assume that

-p->mm != NULL when wake_oom_reaper() is called from task_will_free_mem()

-paths. As a side effect of this patch, this patch also avoids enqueuing

-multiple threads sharing memory via task_will_free_mem(current) path.

-

-Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>

-Reported-by: Arkadiusz Miśkiewicz <a.miskiewicz@gmail.com>

-Fixes: af8e15cc85a25315 ("oom, oom_reaper: do not enqueue task if it is on the oom_reaper_list head")

----

- mm/oom_kill.c | 28 +++++++++++++---------------

- 1 file changed, 13 insertions(+), 15 deletions(-)

-

-diff --git a/mm/oom_kill.c b/mm/oom_kill.c

-index f0e8cd9..457f240 100644

---- a/mm/oom_kill.c

-+++ b/mm/oom_kill.c

-@@ -505,14 +505,6 @@ bool __oom_reap_task_mm(struct mm_struct *mm)

- 	struct vm_area_struct *vma;

- 	bool ret = true;

- 

--	/*

--	 * Tell all users of get_user/copy_from_user etc... that the content

--	 * is no longer stable. No barriers really needed because unmapping

--	 * should imply barriers already and the reader would hit a page fault

--	 * if it stumbled over a reaped memory.

--	 */

--	set_bit(MMF_UNSTABLE, &mm->flags);

--

- 	for (vma = mm->mmap ; vma; vma = vma->vm_next) {

- 		if (!can_madv_dontneed_vma(vma))

- 			continue;

-@@ -645,10 +637,15 @@ static int oom_reaper(void *unused)

- 	return 0;

- }

- 

--static void wake_oom_reaper(struct task_struct *tsk)

-+static void wake_oom_reaper(struct task_struct *tsk, struct mm_struct *mm)

- {

--	/* tsk is already queued? */

--	if (tsk == oom_reaper_list || tsk->oom_reaper_list)

-+	/*

-+	 * Tell all users of get_user/copy_from_user etc... that the content

-+	 * is no longer stable. No barriers really needed because unmapping

-+	 * should imply barriers already and the reader would hit a page fault

-+	 * if it stumbled over a reaped memory.

-+	 */

-+	if (test_and_set_bit(MMF_UNSTABLE, &mm->flags))

- 		return;

- 

- 	get_task_struct(tsk);

-@@ -668,7 +665,8 @@ static int __init oom_init(void)

- }

- subsys_initcall(oom_init)

- #else

--static inline void wake_oom_reaper(struct task_struct *tsk)

-+static inline void wake_oom_reaper(struct task_struct *tsk,

-+				   struct mm_struct *mm)

- {

- }

- #endif /* CONFIG_MMU */

-@@ -915,7 +913,7 @@ static void __oom_kill_process(struct task_struct *victim)

- 	rcu_read_unlock();

- 

- 	if (can_oom_reap)

--		wake_oom_reaper(victim);

-+		wake_oom_reaper(victim, mm);

- 

- 	mmdrop(mm);

- 	put_task_struct(victim);

-@@ -955,7 +953,7 @@ static void oom_kill_process(struct oom_control *oc, const char *message)

- 	task_lock(p);

- 	if (task_will_free_mem(p)) {

- 		mark_oom_victim(p);

--		wake_oom_reaper(p);

-+		wake_oom_reaper(p, p->mm);

- 		task_unlock(p);

- 		put_task_struct(p);

- 		return;

-@@ -1085,7 +1083,7 @@ bool out_of_memory(struct oom_control *oc)

- 	 */

- 	if (task_will_free_mem(current)) {

- 		mark_oom_victim(current);

--		wake_oom_reaper(current);

-+		wake_oom_reaper(current, current->mm);

- 		return true;

- 	}

- 

--- 

-1.8.3.1

-

+
+From 9c9e935fc038342c48461aabca666f1b544e32b1 Mon Sep 17 00:00:00 2001
+From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
+Date: Sat, 26 Jan 2019 21:57:25 +0900
+Subject: [PATCH v2] oom, oom_reaper: do not enqueue same task twice
+
+Arkadiusz reported that enabling memcg's group oom killing causes
+strange memcg statistics where there is no task in a memcg despite
+the number of tasks in that memcg is not 0. It turned out that there
+is a bug in wake_oom_reaper() which allows enqueuing same task twice
+which makes impossible to decrease the number of tasks in that memcg
+due to a refcount leak.
+
+This bug existed since the OOM reaper became invokable from
+task_will_free_mem(current) path in out_of_memory() in Linux 4.7,
+but memcg's group oom killing made it easier to trigger this bug by
+calling wake_oom_reaper() on the same task from one out_of_memory()
+request.
+
+Fix this bug using an approach used by commit 855b018325737f76
+("oom, oom_reaper: disable oom_reaper for oom_kill_allocating_task").
+As a side effect of this patch, this patch also avoids enqueuing
+multiple threads sharing memory via task_will_free_mem(current) path.
+
+Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
+Reported-by: Arkadiusz Miśkiewicz <arekm@maven.pl>
+Tested-by: Arkadiusz Miśkiewicz <arekm@maven.pl>
+Fixes: af8e15cc85a25315 ("oom, oom_reaper: do not enqueue task if it is on the oom_reaper_list head")
+---
+ mm/oom_kill.c | 17 +++++++----------
+ 1 file changed, 7 insertions(+), 10 deletions(-)
+
+diff --git a/mm/oom_kill.c b/mm/oom_kill.c
+index f0e8cd9..057bfee 100644
+--- a/mm/oom_kill.c
++++ b/mm/oom_kill.c
+@@ -505,14 +505,6 @@ bool __oom_reap_task_mm(struct mm_struct *mm)
+ 	struct vm_area_struct *vma;
+ 	bool ret = true;
+ 
+-	/*
+-	 * Tell all users of get_user/copy_from_user etc... that the content
+-	 * is no longer stable. No barriers really needed because unmapping
+-	 * should imply barriers already and the reader would hit a page fault
+-	 * if it stumbled over a reaped memory.
+-	 */
+-	set_bit(MMF_UNSTABLE, &mm->flags);
+-
+ 	for (vma = mm->mmap ; vma; vma = vma->vm_next) {
+ 		if (!can_madv_dontneed_vma(vma))
+ 			continue;
+@@ -647,8 +639,13 @@ static int oom_reaper(void *unused)
+ 
+ static void wake_oom_reaper(struct task_struct *tsk)
+ {
+-	/* tsk is already queued? */
+-	if (tsk == oom_reaper_list || tsk->oom_reaper_list)
++	/*
++	 * Tell all users of get_user/copy_from_user etc... that the content
++	 * is no longer stable. No barriers really needed because unmapping
++	 * should imply barriers already and the reader would hit a page fault
++	 * if it stumbled over a reaped memory.
++	 */
++	if (test_and_set_bit(MMF_UNSTABLE, &tsk->signal->oom_mm->flags))
+ 		return;
+ 
+ 	get_task_struct(tsk);
+-- 
+1.8.3.1
+