[Vserver] [RFC][PATCH 6/9] proc interface to tsk->child_container_id

From: Dave Hansen <haveblue_at_us.ibm.com>
Date: Mon 24 Oct 2005 - 17:21:30 BST
Message-Id: <20051024162130.300E11F8@localhost>

You might have more than one process which is restored which wants the
same pid. A container is a group of processes which share namespace.
In this case, pid namespace. The idea for now is that everything is
in "container 0" unless otherwise specified.

This /proc file allows a task to set the container id of any of its
children.

This is mostly a hack for now, to demonstrate what can be done.

---
 linux-2.6.14-rc5-dave/fs/proc/base.c        |   58 ++++++++++++++++++++++++++++
 linux-2.6.14-rc5-dave/include/linux/sched.h |    2 
 2 files changed, 60 insertions(+)
diff -puN fs/proc/base.c~C1-proc-interface-to-child_container_id fs/proc/base.c
--- linux-2.6.14-rc5/fs/proc/base.c~C1-proc-interface-to-child_container_id	2005-10-24 17:55:40.000000000 +0200
+++ linux-2.6.14-rc5-dave/fs/proc/base.c	2005-10-24 17:55:40.000000000 +0200
@@ -164,6 +164,8 @@ enum pid_directory_inos {
 #endif
 	PROC_TID_OOM_SCORE,
 	PROC_TID_OOM_ADJUST,
+	PROC_TID_CHILD_CONTAINER_ID,
+	PROC_TGID_CHILD_CONTAINER_ID,
 
 	/* Add new entries before this */
 	PROC_TID_FD_DIR = 0x8000,	/* 0x8000-0xffff */
@@ -216,6 +218,7 @@ static struct pid_entry tgid_base_stuff[
 #endif
 	E(PROC_TGID_OOM_SCORE, "oom_score",S_IFREG|S_IRUGO),
 	E(PROC_TGID_OOM_ADJUST,"oom_adj", S_IFREG|S_IRUGO|S_IWUSR),
+	E(PROC_TGID_CHILD_CONTAINER_ID, "child_container_id", S_IFREG|S_IRUGO|S_IWUSR),
 #ifdef CONFIG_AUDITSYSCALL
 	E(PROC_TGID_LOGINUID, "loginuid", S_IFREG|S_IWUSR|S_IRUGO),
 #endif
@@ -258,6 +261,7 @@ static struct pid_entry tid_base_stuff[]
 #endif
 	E(PROC_TID_OOM_SCORE,  "oom_score",S_IFREG|S_IRUGO),
 	E(PROC_TID_OOM_ADJUST, "oom_adj", S_IFREG|S_IRUGO|S_IWUSR),
+	E(PROC_TID_CHILD_CONTAINER_ID, "child_container_id", S_IFREG|S_IRUGO|S_IWUSR),
 #ifdef CONFIG_AUDITSYSCALL
 	E(PROC_TID_LOGINUID, "loginuid", S_IFREG|S_IWUSR|S_IRUGO),
 #endif
@@ -910,6 +914,56 @@ static struct file_operations proc_oom_a
 	.write		= oom_adjust_write,
 };
 
+static ssize_t proc_child_container_id_read(struct file *file, char __user *buf,
+				size_t count, loff_t *ppos)
+{
+	struct task_struct *task = proc_task(file->f_dentry->d_inode);
+	char buffer[8];
+	size_t len;
+	int child_container_id = task->child_container_id;
+	loff_t __ppos = *ppos;
+
+	len = sprintf(buffer, "%i\n", child_container_id);
+	if (__ppos >= len)
+		return 0;
+	if (count > len-__ppos)
+		count = len-__ppos;
+	if (copy_to_user(buf, buffer + __ppos, count))
+		return -EFAULT;
+	*ppos = __ppos + count;
+	return count;
+}
+
+static ssize_t proc_child_container_id_write(struct file *file, const char __user *buf,
+				size_t count, loff_t *ppos)
+{
+	struct task_struct *task = proc_task(file->f_dentry->d_inode);
+	char buffer[8], *end;
+	int child_container_id;
+
+	if (!capable(CAP_SYS_RESOURCE))
+		return -EPERM;
+	memset(buffer, 0, 8);
+	if (count > 6)
+		count = 6;
+	if (copy_from_user(buffer, buf, count))
+		return -EFAULT;
+	child_container_id = simple_strtol(buffer, &end, 0);
+	if (child_container_id < 0 || child_container_id > MAX_CONTAINER_ID)
+		return -EINVAL;
+	if (*end == '\n')
+		end++;
+	task->child_container_id = child_container_id;
+	if (end - buffer == 0)
+		return -EIO;
+	return end - buffer;
+}
+
+static struct file_operations proc_child_container_id_operations = {
+	.read		= proc_child_container_id_read,
+	.write		= proc_child_container_id_write,
+};
+
 static struct inode_operations proc_mem_inode_operations = {
 	.permission	= proc_permission,
 };
@@ -1748,6 +1802,10 @@ static struct dentry *proc_pident_lookup
 		case PROC_TGID_OOM_ADJUST:
 			inode->i_fop = &proc_oom_adjust_operations;
 			break;
+		case PROC_TID_CHILD_CONTAINER_ID:
+		case PROC_TGID_CHILD_CONTAINER_ID:
+			inode->i_fop = &proc_child_container_id_operations;
+			break;
 #ifdef CONFIG_AUDITSYSCALL
 		case PROC_TID_LOGINUID:
 		case PROC_TGID_LOGINUID:
diff -puN include/linux/sched.h~C1-proc-interface-to-child_container_id include/linux/sched.h
--- linux-2.6.14-rc5/include/linux/sched.h~C1-proc-interface-to-child_container_id	2005-10-24 17:55:40.000000000 +0200
+++ linux-2.6.14-rc5-dave/include/linux/sched.h	2005-10-24 17:55:40.000000000 +0200
@@ -726,6 +726,8 @@ struct task_struct {
 /* process credentials */
 	uid_t uid,euid,suid,fsuid;
 	gid_t gid,egid,sgid,fsgid;
+#define MAX_CONTAINER_ID 1024
+	int child_container_id;
 	struct group_info *group_info;
 	kernel_cap_t   cap_effective, cap_inheritable, cap_permitted;
 	unsigned keep_capabilities:1;
_
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Received on Mon Oct 24 17:29:07 2005
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