[RFC][PATCH 1/4] Provide a new procfs interface to set next ipc id

[Nadia.Derbey-6ktuUTfB/bM@public.gmane.org]

[-- Attachment #1: proc_set_next_ipcid.patch --]
[-- Type: text/plain, Size: 6037 bytes --]

[PATCH 01/04]

This patch proposes the procfs facilities needed to feed the id for the
next ipc object to be allocated.

if an
echo XX > /proc/self/next_ipcid
is issued, next ipc object to be created will have XX as its id.

Signed-off-by: Nadia Derbey <Nadia.Derbey-6ktuUTfB/bM@public.gmane.org>

---
 fs/proc/base.c         |   66 +++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/sched.h  |    3 ++
 include/linux/sysids.h |   20 ++++++++++++++
 kernel/Makefile        |    2 -
 kernel/set_nextid.c    |   31 +++++++++++++++++++++++
 5 files changed, 121 insertions(+), 1 deletion(-)

Index: linux-2.6.25-rc3-mm1/include/linux/sysids.h
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6.25-rc3-mm1/include/linux/sysids.h	2008-03-10 11:39:10.000000000 +0100
@@ -0,0 +1,20 @@
+/*
+ * include/linux/sysids.h
+ *
+ * Definitions to support object creation with predefined id.
+ *
+ */
+
+#ifndef _LINUX_SYSIDS_H
+#define _LINUX_SYSIDS_H
+
+#define SYS_ID_IPC 1
+
+struct sys_id {
+	int flag;	/* which id should be set */
+	int ipc;
+};
+
+extern int ipc_set_nextid(struct task_struct *, int id);
+
+#endif /* _LINUX_SYSIDS_H */
Index: linux-2.6.25-rc3-mm1/include/linux/sched.h
===================================================================
--- linux-2.6.25-rc3-mm1.orig/include/linux/sched.h	2008-03-10 09:18:46.000000000 +0100
+++ linux-2.6.25-rc3-mm1/include/linux/sched.h	2008-03-10 09:28:30.000000000 +0100
@@ -87,6 +87,7 @@ struct sched_param {
 #include <linux/task_io_accounting.h>
 #include <linux/kobject.h>
 #include <linux/latencytop.h>
+#include <linux/sysids.h>
 
 #include <asm/processor.h>
 
@@ -1261,6 +1262,8 @@ struct task_struct {
 	int latency_record_count;
 	struct latency_record latency_record[LT_SAVECOUNT];
 #endif
+	/* Id to assign to the next resource to be created */
+	struct sys_id *next_id;
 };
 
 /*
Index: linux-2.6.25-rc3-mm1/fs/proc/base.c
===================================================================
--- linux-2.6.25-rc3-mm1.orig/fs/proc/base.c	2008-03-10 09:19:39.000000000 +0100
+++ linux-2.6.25-rc3-mm1/fs/proc/base.c	2008-03-10 11:22:20.000000000 +0100
@@ -76,6 +76,7 @@
 #include <linux/oom.h>
 #include <linux/elf.h>
 #include <linux/pid_namespace.h>
+#include <linux/ctype.h>
 #include "internal.h"
 
 /* NOTE:
@@ -1080,6 +1081,69 @@ static const struct file_operations proc
 #endif
 
 
+static ssize_t next_ipcid_read(struct file *file, char __user *buf,
+				size_t count, loff_t *ppos)
+{
+	struct task_struct *task;
+	char buffer[PROC_NUMBUF];
+	size_t len;
+	struct sys_id *sid;
+	int next_ipcid;
+
+	task = get_proc_task(file->f_path.dentry->d_inode);
+	if (!task)
+		return -ESRCH;
+
+	sid = task->next_id;
+	next_ipcid = (sid) ? ((sid->flag & SYS_ID_IPC) ? sid->ipc : -1)
+			: -1;
+
+	put_task_struct(task);
+
+	len = snprintf(buffer, sizeof(buffer), "%i\n", next_ipcid);
+
+	return simple_read_from_buffer(buf, count, ppos, buffer, len);
+}
+
+static ssize_t next_ipcid_write(struct file *file, const char __user *buf,
+				size_t count, loff_t *ppos)
+{
+	struct inode *inode = file->f_path.dentry->d_inode;
+	char buffer[PROC_NUMBUF], *end;
+	int next_ipcid;
+	int rc;
+
+	if (pid_task(proc_pid(inode), PIDTYPE_PID) != current)
+		return -EPERM;
+
+	memset(buffer, 0, sizeof(buffer));
+	if (count > sizeof(buffer) - 1)
+		count = sizeof(buffer) - 1;
+	if (copy_from_user(buffer, buf, count))
+		return -EFAULT;
+
+	next_ipcid = simple_strtol(buffer, &end, 0);
+	if (next_ipcid < 0 || end == buffer)
+		return -EINVAL;
+
+	while (isspace(*end))
+		end++;
+
+	rc = ipc_set_nextid(current, next_ipcid);
+	if (rc)
+		return rc;
+
+	if (end - buffer == 0)
+		return -EIO;
+	return end - buffer;
+}
+
+static const struct file_operations proc_next_ipcid_operations = {
+	.read		= next_ipcid_read,
+	.write		= next_ipcid_write,
+};
+
+
 #ifdef CONFIG_SCHED_DEBUG
 /*
  * Print out various scheduling related per-task fields:
@@ -2391,6 +2455,7 @@ static const struct pid_entry tgid_base_
 #ifdef CONFIG_TASK_IO_ACCOUNTING
 	INF("io",	S_IRUGO, pid_io_accounting),
 #endif
+	REG("next_ipcid", S_IRUGO|S_IWUSR, next_ipcid),
 };
 
 static int proc_tgid_base_readdir(struct file * filp,
@@ -2716,6 +2781,7 @@ static const struct pid_entry tid_base_s
 #ifdef CONFIG_FAULT_INJECTION
 	REG("make-it-fail", S_IRUGO|S_IWUSR, fault_inject),
 #endif
+	REG("next_ipcid", S_IRUGO|S_IWUSR, next_ipcid),
 };
 
 static int proc_tid_base_readdir(struct file * filp,
Index: linux-2.6.25-rc3-mm1/kernel/Makefile
===================================================================
--- linux-2.6.25-rc3-mm1.orig/kernel/Makefile	2008-03-10 09:19:01.000000000 +0100
+++ linux-2.6.25-rc3-mm1/kernel/Makefile	2008-03-10 09:41:27.000000000 +0100
@@ -9,7 +9,7 @@ obj-y     = sched.o fork.o exec_domain.o
 	    rcupdate.o extable.o params.o posix-timers.o \
 	    kthread.o wait.o kfifo.o sys_ni.o posix-cpu-timers.o mutex.o \
 	    hrtimer.o rwsem.o nsproxy.o srcu.o semaphore.o \
-	    notifier.o ksysfs.o pm_qos_params.o
+	    notifier.o ksysfs.o pm_qos_params.o set_nextid.o
 
 obj-$(CONFIG_SYSCTL_SYSCALL_CHECK) += sysctl_check.o
 obj-$(CONFIG_STACKTRACE) += stacktrace.o
Index: linux-2.6.25-rc3-mm1/kernel/set_nextid.c
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6.25-rc3-mm1/kernel/set_nextid.c	2008-03-10 10:09:47.000000000 +0100
@@ -0,0 +1,31 @@
+/*
+ * linux/kernel/set_nextid.c
+ *
+ *
+ * Provide the XXX_set_nextid() routines (called from fs/proc/base.c).
+ * They allow to specify the id for the next resource to be allocated,
+ * instead of letting the allocator set it for us.
+ */
+
+#include <linux/sched.h>
+
+
+
+int ipc_set_nextid(struct task_struct *task, int id)
+{
+	struct sys_id *sid;
+
+	sid = task->next_id;
+	if (!sid) {
+		sid = kzalloc(sizeof(*sid), GFP_KERNEL);
+		if (!sid)
+			return -ENOMEM;
+		task->next_id = sid;
+	}
+
+	sid->ipc = id;
+	sid->flag |= SYS_ID_IPC;
+
+	return 0;
+}
+

--