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Subject[PATCH 01/15] proc: pick out a function to iterate task children
Date
This function will be used in task_diag.

Signed-off-by: Andrey Vagin <avagin@openvz.org>
---
fs/proc/array.c | 53 +++++++++++++++++++++++++++++++++--------------------
fs/proc/internal.h | 3 +++
2 files changed, 36 insertions(+), 20 deletions(-)

diff --git a/fs/proc/array.c b/fs/proc/array.c
index b6c00ce..3eceab1 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -593,31 +593,25 @@ int proc_pid_statm(struct seq_file *m, struct pid_namespace *ns,
}

#ifdef CONFIG_PROC_CHILDREN
-static struct pid *
-get_children_pid(struct inode *inode, struct pid *pid_prev, loff_t pos)
+struct task_struct *
+task_next_child(struct task_struct *parent, struct task_struct *prev, unsigned int pos)
{
- struct task_struct *start, *task;
- struct pid *pid = NULL;
-
- read_lock(&tasklist_lock);
-
- start = pid_task(proc_pid(inode), PIDTYPE_PID);
- if (!start)
- goto out;
+ struct task_struct *task;

/*
* 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 &&
+ if (prev) {
+ task = prev;
+ if (task && task->real_parent == parent &&
!(list_empty(&task->sibling))) {
- if (list_is_last(&task->sibling, &start->children))
+ if (list_is_last(&task->sibling, &parent->children)) {
+ task = NULL;
goto out;
+ }
task = list_first_entry(&task->sibling,
struct task_struct, sibling);
- pid = get_pid(task_pid(task));
goto out;
}
}
@@ -637,12 +631,31 @@ get_children_pid(struct inode *inode, struct pid *pid_prev, loff_t pos)
* So one need to stop or freeze the leader and all
* its children to get a precise result.
*/
- list_for_each_entry(task, &start->children, sibling) {
- if (pos-- == 0) {
- pid = get_pid(task_pid(task));
- break;
- }
+ list_for_each_entry(task, &parent->children, sibling) {
+ if (pos-- == 0)
+ goto out;
}
+ task = NULL;
+out:
+ return task;
+}
+
+static struct pid *
+get_children_pid(struct inode *inode, struct pid *prev_pid, loff_t pos)
+{
+ struct task_struct *start, *task, *prev;
+ struct pid *pid = NULL;
+
+ read_lock(&tasklist_lock);
+ start = pid_task(proc_pid(inode), PIDTYPE_PID);
+ if (!start)
+ goto out;
+
+ prev = prev_pid ? pid_task(prev_pid, PIDTYPE_PID) : NULL;
+
+ task = task_next_child(start, prev, pos);
+ if (task)
+ pid = get_pid(task_pid(task));

out:
read_unlock(&tasklist_lock);
diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index aa27810..969e05b 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -303,3 +303,6 @@ extern unsigned long task_statm(struct mm_struct *,
unsigned long *, unsigned long *,
unsigned long *, unsigned long *);
extern void task_mem(struct seq_file *, struct mm_struct *);
+
+struct task_struct *
+task_next_child(struct task_struct *parent, struct task_struct *prev, unsigned int pos);
--
2.5.5
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