mm, oom: reorganize the oom report in dump_header

OOM report contains several sections.  The first one is the allocation
context that has triggered the OOM.  Then we have cpuset context followed
by the stack trace of the OOM path.  The tird one is the OOM memory
information.  Followed by the current memory state of all system tasks.
At last, we will show oom eligible tasks and the information about the
chosen oom victim.

One thing that makes parsing more awkward than necessary is that we do not
have a single and easily parsable line about the oom context.  This patch
is reorganizing the oom report to

1) who invoked oom and what was the allocation request

[  515.902945] tuned invoked oom-killer: gfp_mask=0x6200ca(GFP_HIGHUSER_MOVABLE), order=0, oom_score_adj=0

2) OOM stack trace

[  515.904273] CPU: 24 PID: 1809 Comm: tuned Not tainted 4.20.0-rc3+ #3
[  515.905518] Hardware name: Inspur SA5212M4/YZMB-00370-107, BIOS 4.1.10 11/14/2016
[  515.906821] Call Trace:
[  515.908062]  dump_stack+0x5a/0x73
[  515.909311]  dump_header+0x55/0x28c
[  515.914260]  oom_kill_process+0x2d8/0x300
[  515.916708]  out_of_memory+0x145/0x4a0
[  515.917932]  __alloc_pages_slowpath+0x7d2/0xa16
[  515.919157]  __alloc_pages_nodemask+0x277/0x290
[  515.920367]  filemap_fault+0x3d0/0x6c0
[  515.921529]  ? filemap_map_pages+0x2b8/0x420
[  515.922709]  ext4_filemap_fault+0x2c/0x40 [ext4]
[  515.923884]  __do_fault+0x20/0x80
[  515.925032]  __handle_mm_fault+0xbc0/0xe80
[  515.926195]  handle_mm_fault+0xfa/0x210
[  515.927357]  __do_page_fault+0x233/0x4c0
[  515.928506]  do_page_fault+0x32/0x140
[  515.929646]  ? page_fault+0x8/0x30
[  515.930770]  page_fault+0x1e/0x30

3) OOM memory information

[  515.958093] Mem-Info:
[  515.959647] active_anon:26501758 inactive_anon:1179809 isolated_anon:0
 active_file:4402672 inactive_file:483963 isolated_file:1344
 unevictable:0 dirty:4886753 writeback:0 unstable:0
 slab_reclaimable:148442 slab_unreclaimable:18741
 mapped:1347 shmem:1347 pagetables:58669 bounce:0
 free:88663 free_pcp:0 free_cma:0
...

4) current memory state of all system tasks

[  516.079544] [    744]     0   744     9211     1345   114688       82             0 systemd-journal
[  516.082034] [    787]     0   787    31764        0   143360       92             0 lvmetad
[  516.084465] [    792]     0   792    10930        1   110592      208         -1000 systemd-udevd
[  516.086865] [   1199]     0  1199    13866        0   131072      112         -1000 auditd
[  516.089190] [   1222]     0  1222    31990        1   110592      157             0 smartd
[  516.091477] [   1225]     0  1225     4864       85    81920       43             0 irqbalance
[  516.093712] [   1226]     0  1226    52612        0   258048      426             0 abrtd
[  516.112128] [   1280]     0  1280   109774       55   299008      400             0 NetworkManager
[  516.113998] [   1295]     0  1295    28817       37    69632       24             0 ksmtuned
[  516.144596] [  10718]     0 10718  2622484  1721372 15998976   267219             0 panic
[  516.145792] [  10719]     0 10719  2622484  1164767  9818112    53576             0 panic
[  516.146977] [  10720]     0 10720  2622484  1174361  9904128    53709             0 panic
[  516.148163] [  10721]     0 10721  2622484  1209070 10194944    54824             0 panic
[  516.149329] [  10722]     0 10722  2622484  1745799 14774272    91138             0 panic

5) oom context (contrains and the chosen victim).

oom-kill:constraint=CONSTRAINT_NONE,nodemask=(null),cpuset=/,mems_allowed=0-1,task=panic,pid=10737,uid=0

An admin can easily get the full oom context at a single line which
makes parsing much easier.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: yuzhoujian <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: "Kirill A . Shutemov" <[email protected]>
Cc: Roman Gushchin <[email protected]>
Cc: Tetsuo Handa <[email protected]>
Cc: Yang Shi <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: yuzhoujian

include/linux/oom.h

@@ -15,6 +15,13 @@ struct notifier_block;
 struct mem_cgroup;
 struct task_struct;
 
+enum oom_constraint {
+	CONSTRAINT_NONE,
+	CONSTRAINT_CPUSET,
+	CONSTRAINT_MEMORY_POLICY,
+	CONSTRAINT_MEMCG,
+};
+
 /*
  * Details of the page allocation that triggered the oom killer that are used to
  * determine what should be killed.
@@ -42,6 +49,9 @@ struct oom_control {
 	unsigned long totalpages;
 	struct task_struct *chosen;
 	unsigned long chosen_points;
+
+	/* Used to print the constraint info. */
+	enum oom_constraint constraint;
 };
 
 extern struct mutex oom_lock;

kernel/cgroup/cpuset.c

@@ -2666,9 +2666,9 @@ void cpuset_print_current_mems_allowed(void)
 	rcu_read_lock();
 
 	cgrp = task_cs(current)->css.cgroup;
-	pr_info("%s cpuset=", current->comm);
+	pr_cont(",cpuset=");
 	pr_cont_cgroup_name(cgrp);
-	pr_cont(" mems_allowed=%*pbl\n",
+	pr_cont(",mems_allowed=%*pbl",
 		nodemask_pr_args(&current->mems_allowed));
 
 	rcu_read_unlock();

mm/oom_kill.c

@@ -245,11 +245,11 @@ unsigned long oom_badness(struct task_struct *p, struct mem_cgroup *memcg,
 	return points > 0 ? points : 1;
 }
 
-enum oom_constraint {
-	CONSTRAINT_NONE,
-	CONSTRAINT_CPUSET,
-	CONSTRAINT_MEMORY_POLICY,
-	CONSTRAINT_MEMCG,
+static const char * const oom_constraint_text[] = {
+	[CONSTRAINT_NONE] = "CONSTRAINT_NONE",
+	[CONSTRAINT_CPUSET] = "CONSTRAINT_CPUSET",
+	[CONSTRAINT_MEMORY_POLICY] = "CONSTRAINT_MEMORY_POLICY",
+	[CONSTRAINT_MEMCG] = "CONSTRAINT_MEMCG",
 };
 
 /*
@@ -428,16 +428,25 @@ static void dump_tasks(struct mem_cgroup *memcg, const nodemask_t *nodemask)
 	rcu_read_unlock();
 }
 
+static void dump_oom_summary(struct oom_control *oc, struct task_struct *victim)
+{
+	/* one line summary of the oom killer context. */
+	pr_info("oom-kill:constraint=%s,nodemask=%*pbl",
+			oom_constraint_text[oc->constraint],
+			nodemask_pr_args(oc->nodemask));
+	cpuset_print_current_mems_allowed();
+	pr_cont(",task=%s,pid=%d,uid=%d\n", victim->comm, victim->pid,
+		from_kuid(&init_user_ns, task_uid(victim)));
+}
+
 static void dump_header(struct oom_control *oc, struct task_struct *p)
 {
-	pr_warn("%s invoked oom-killer: gfp_mask=%#x(%pGg), nodemask=%*pbl, order=%d, oom_score_adj=%hd\n",
-		current->comm, oc->gfp_mask, &oc->gfp_mask,
-		nodemask_pr_args(oc->nodemask), oc->order,
+	pr_warn("%s invoked oom-killer: gfp_mask=%#x(%pGg), order=%d, oom_score_adj=%hd\n",
+		current->comm, oc->gfp_mask, &oc->gfp_mask, oc->order,
 			current->signal->oom_score_adj);
 	if (!IS_ENABLED(CONFIG_COMPACTION) && oc->order)
 		pr_warn("COMPACTION is disabled!!!\n");
 
-	cpuset_print_current_mems_allowed();
 	dump_stack();
 	if (is_memcg_oom(oc))
 		mem_cgroup_print_oom_info(oc->memcg, p);
@@ -448,6 +457,8 @@ static void dump_header(struct oom_control *oc, struct task_struct *p)
 	}
 	if (sysctl_oom_dump_tasks)
 		dump_tasks(oc->memcg, oc->nodemask);
+	if (p)
+		dump_oom_summary(oc, p);
 }
 
 /*

mm/page_alloc.c

@@ -3517,13 +3517,13 @@ void warn_alloc(gfp_t gfp_mask, nodemask_t *nodemask, const char *fmt, ...)
 	va_start(args, fmt);
 	vaf.fmt = fmt;
 	vaf.va = &args;
-	pr_warn("%s: %pV, mode:%#x(%pGg), nodemask=%*pbl\n",
+	pr_warn("%s: %pV, mode:%#x(%pGg), nodemask=%*pbl",
 			current->comm, &vaf, gfp_mask, &gfp_mask,
 			nodemask_pr_args(nodemask));
 	va_end(args);
 
 	cpuset_print_current_mems_allowed();
-
+	pr_cont("\n");
 	dump_stack();
 	warn_alloc_show_mem(gfp_mask, nodemask);
 }