linux-kernel - [PATCH] pids: introduce find_get_task_by

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Message-Id: <1509023278-20604-1-git-send-email-rppt@linux.vnet.ibm.com>
Date:   Thu, 26 Oct 2017 16:07:58 +0300
From:   Mike Rapoport <rppt@...ux.vnet.ibm.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Darren Hart <dvhart@...radead.org>,
        Oleg Nesterov <oleg@...hat.com>,
        Balbir Singh <bsingharora@...il.com>,
        linux-mm <linux-mm@...ck.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>
Subject: [PATCH] pids: introduce find_get_task_by_vpid helper

There are several functions that do find_task_by_vpid() followed by
get_task_struct(). We can use a helper function instead.

Signed-off-by: Mike Rapoport <rppt@...ux.vnet.ibm.com>
---
 include/linux/sched.h  |  5 +++++
 kernel/futex.c         |  7 +------
 kernel/pid.c           | 13 +++++++++++++
 kernel/ptrace.c        |  6 +-----
 kernel/taskstats.c     |  6 +-----
 mm/process_vm_access.c |  6 +-----
 6 files changed, 22 insertions(+), 21 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 26a7df4e558c..4c3af5255fcf 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1484,6 +1484,11 @@ static inline struct thread_info *task_thread_info(struct task_struct *task)
 extern struct task_struct *find_task_by_vpid(pid_t nr);
 extern struct task_struct *find_task_by_pid_ns(pid_t nr, struct pid_namespace *ns);
 
+/*
+ * find a task by its virtual pid and get the task struct
+ */
+extern struct task_struct *find_get_task_by_vpid(pid_t nr);
+
 extern int wake_up_state(struct task_struct *tsk, unsigned int state);
 extern int wake_up_process(struct task_struct *tsk);
 extern void wake_up_new_task(struct task_struct *tsk);
diff --git a/kernel/futex.c b/kernel/futex.c
index 0518a0bfc746..6446aa9f2288 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -870,12 +870,7 @@ static struct task_struct *futex_find_get_task(pid_t pid)
 {
 	struct task_struct *p;
 
-	rcu_read_lock();
-	p = find_task_by_vpid(pid);
-	if (p)
-		get_task_struct(p);
-
-	rcu_read_unlock();
+	p = find_get_task_by_vpid(pid);
 
 	return p;
 }
diff --git a/kernel/pid.c b/kernel/pid.c
index 020dedbdf066..ead086b0ef8e 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -462,6 +462,19 @@ struct task_struct *find_task_by_vpid(pid_t vnr)
 	return find_task_by_pid_ns(vnr, task_active_pid_ns(current));
 }
 
+struct task_struct *find_get_task_by_vpid(pid_t nr)
+{
+	struct task_struct *task;
+
+	rcu_read_lock();
+	task = find_task_by_vpid(nr);
+	if (task)
+		get_task_struct(task);
+	rcu_read_unlock();
+
+	return task;
+}
+
 struct pid *get_task_pid(struct task_struct *task, enum pid_type type)
 {
 	struct pid *pid;
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 84b1367935e4..91efc97674ce 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -1103,11 +1103,7 @@ static struct task_struct *ptrace_get_task_struct(pid_t pid)
 {
 	struct task_struct *child;
 
-	rcu_read_lock();
-	child = find_task_by_vpid(pid);
-	if (child)
-		get_task_struct(child);
-	rcu_read_unlock();
+	child = find_get_task_by_vpid(pid);
 
 	if (!child)
 		return ERR_PTR(-ESRCH);
diff --git a/kernel/taskstats.c b/kernel/taskstats.c
index 4559e914452b..4e62a4a8fa91 100644
--- a/kernel/taskstats.c
+++ b/kernel/taskstats.c
@@ -194,11 +194,7 @@ static int fill_stats_for_pid(pid_t pid, struct taskstats *stats)
 {
 	struct task_struct *tsk;
 
-	rcu_read_lock();
-	tsk = find_task_by_vpid(pid);
-	if (tsk)
-		get_task_struct(tsk);
-	rcu_read_unlock();
+	tsk = find_get_task_by_vpid(pid);
 	if (!tsk)
 		return -ESRCH;
 	fill_stats(current_user_ns(), task_active_pid_ns(current), tsk, stats);
diff --git a/mm/process_vm_access.c b/mm/process_vm_access.c
index 8973cd231ece..16424b9ae424 100644
--- a/mm/process_vm_access.c
+++ b/mm/process_vm_access.c
@@ -197,11 +197,7 @@ static ssize_t process_vm_rw_core(pid_t pid, struct iov_iter *iter,
 	}
 
 	/* Get process information */
-	rcu_read_lock();
-	task = find_task_by_vpid(pid);
-	if (task)
-		get_task_struct(task);
-	rcu_read_unlock();
+	task = find_get_task_by_vpid(pid);
 	if (!task) {
 		rc = -ESRCH;
 		goto free_proc_pages;
-- 
2.7.4