linux-kernel - [PATCH RFC 05/13] fs: Refactoring in get_children

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Date:	Mon, 25 May 2015 20:45:05 +0300
From:	Kirill Tkhai <ktkhai@...n.com>
To:	<linux-kernel@...r.kernel.org>
CC:	Oleg Nesterov <oleg@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...hat.com>,
	"Peter Zijlstra" <peterz@...radead.org>,
	Michal Hocko <mhocko@...e.cz>,
	"Rik van Riel" <riel@...hat.com>,
	Ionut Alexa <ionut.m.alexa@...il.com>,
	Peter Hurley <peter@...leysoftware.com>,
	Kirill Tkhai <tkhai@...dex.ru>
Subject: [PATCH RFC 05/13] fs: Refactoring in get_children_pid()

This will be used in next patches. No functionality change.

Signed-off-by: Kirill Tkhai <ktkhai@...n.com>
---
 fs/proc/array.c |   28 ++++++++++++++++------------
 1 file changed, 16 insertions(+), 12 deletions(-)

diff --git a/fs/proc/array.c b/fs/proc/array.c
index fd02a9e..e2f21c0 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -576,9 +576,7 @@ get_children_pid(struct inode *inode, struct pid *pid_prev, loff_t pos)
 	struct task_struct *start, *task;
 	struct pid *pid = NULL;
 
-	read_lock(&tasklist_lock);
-
-	start = pid_task(proc_pid(inode), PIDTYPE_PID);
+	start = get_pid_task(proc_pid(inode), PIDTYPE_PID);
 	if (!start)
 		goto out;
 
@@ -586,18 +584,21 @@ get_children_pid(struct inode *inode, struct pid *pid_prev, loff_t pos)
 	 * Lets try to continue searching first, this gives
 	 * us significant speedup on children-rich processes.
 	 */
-	if (pid_prev) {
-		task = pid_task(pid_prev, PIDTYPE_PID);
-		if (task && task->real_parent == start &&
-		    !(list_empty(&task->sibling))) {
-			if (list_is_last(&task->sibling, &start->children))
-				goto out;
+	task = get_pid_task(pid_prev, PIDTYPE_PID);
+	if (!task)
+		goto put_start;
+
+	read_lock(&tasklist_lock);
+	if (task->real_parent == start && !(list_empty(&task->sibling))) {
+		put_task_struct(task);
+		if (!list_is_last(&task->sibling, &start->children)) {
 			task = list_first_entry(&task->sibling,
-						struct task_struct, sibling);
+					struct task_struct, sibling);
 			pid = get_pid(task_pid(task));
-			goto out;
 		}
+		goto unlock;
 	}
+	put_task_struct(task);
 
 	/*
 	 * Slow search case.
@@ -621,8 +622,11 @@ get_children_pid(struct inode *inode, struct pid *pid_prev, loff_t pos)
 		}
 	}
 
-out:
+unlock:
 	read_unlock(&tasklist_lock);
+put_start:
+	put_task_struct(start);
+out:
 	return pid;
 }
 



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