[Devel] [RFC][PATCH 0/2] pipe: checkpoint and restart for pipe; brief description and test interface

[Masahiko Takahashi]

Hi everyone,

I would like to post a small patch that implements pipe checkpoint
and restart functionality.

The patch supports pipe buffers used with splice/vmsplice systemcall.
Usually, spliced buffers' pages are in memory cache because their data
are read from an filesystem. However the patch doesn't treat buffers'
pages as cached memory when restoring. If trying to treat as cached
memory, each buffer's page should be tagged with its filename when
checkpointing. This is not a difficult implementation, but I'm still
wondering this is worth implementing...

   [RFC][PATCH 1/2] pipe: header file and removal of dupfd()'s static
   [RFC][PATCH 2/2] pipe: checkpoint and restart entity

The patch is for kernel 2.6.19.2 and tested with pipe, splice and
vmsplice systemcalls.

Interfaces:
   int ckpoint_pipe(struct file *filp, struct cr_pipe *img)
        A pipe (specified by "filp") and its information/buffers are
        checkpointed to image buffer "img". (img must has enough memory)

   int restore_pipe(int *fd, struct cr_pipe *img)
        The checkpointed pipe information/buffers "img" is restored
        to kernel and installed to the current process's file
        descriptors "fd". fd[0] is pipe for read and fd[1] for write.

TODO:
        - Non-blocking (signal delivery) and waiting process list.
        - Parameter checks (image buffer size, etc).
        - Error checks.
        - Support file descriptor sharing.
        - More tests.


The attached source is a test/debug interface for pipe checkpoint and
restart on Linux 2.6.19.2. I borrowed this from OpenVZ patch with some
naming and other changes.


Masahiko.

-------------- next part --------------
--- /dev/null	2006-05-22 07:25:23.000000000 -0700
+++ linux-2.6.19.2/fs/pipe-cr-debug.c	2007-01-22 15:39:05.000000000 -0800
@@ -0,0 +1,115 @@
+#include <linux/mm.h>
+#include <linux/file.h>
+#include <linux/poll.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/fs.h>
+#include <linux/mount.h>
+#include <linux/pipe_fs_i.h>
+#include <linux/uio.h>
+
+#include <linux/device.h>
+
+#include <asm/uaccess.h>
+#include <asm/ioctls.h>
+
+#include <linux/cr.h>
+
+static struct class *crctl_class;
+
+#define	CRCTL_MAJOR	200
+#define	CRCTL_NAME	"crctl"
+
+extern int ckpoint_pipe(struct file *filp, struct cr_pipe *img);
+extern int restore_pipe(int *fd, struct cr_pipe *img);
+
+
+static int cr_open(struct inode *inode, struct file *filp)
+{
+	return 0;
+}
+
+static int cr_release(struct inode *inode, struct file *filp)
+{
+	return 0;
+}
+
+static int crctl_ioctl(struct inode *pino, struct file *filp,
+	   unsigned int cmd, unsigned long arg)
+{
+	int fd[2];
+	struct mig_arg {
+		void    *arg1;
+		void    *arg2;
+	} i;
+
+	switch(cmd) {
+		case 246:
+		{
+			struct file *pipefp;
+			int r, fput;
+
+			if (copy_from_user (&i, (void __user *) arg,
+				sizeof(i))) return -EFAULT;
+			pipefp = fget_light((int) i.arg1, &fput);
+			r = ckpoint_pipe(pipefp, (struct cr_pipe *) i.arg2);
+			fput_light(pipefp, fput);
+			return r;
+		}
+		case 245:
+			if (copy_from_user(&i, (void __user *) arg,
+				sizeof(i))) return -EFAULT;
+			if (copy_from_user(fd, (void __user *) i.arg1,
+				sizeof(int) * 2)) return -EFAULT;
+			return restore_pipe(fd, (struct cr_pipe *) i.arg2);
+	}
+	return 0;
+}
+
+static struct file_operations crctl_fops = {
+	.open		= cr_open,
+	.release	= cr_release,
+	.ioctl		= crctl_ioctl,
+};
+
+static void __exit crctl_exit(void)
+{
+	class_device_destroy(crctl_class, MKDEV(CRCTL_MAJOR, 0));
+	class_destroy(crctl_class);
+	unregister_chrdev(CRCTL_MAJOR, CRCTL_NAME);
+}
+
+static int __init crctl_init(void)
+{
+	int ret;
+	struct class_device *class_err;
+
+	ret = register_chrdev(CRCTL_MAJOR, CRCTL_NAME, &crctl_fops);
+	if (ret < 0)
+		goto out;
+
+	crctl_class = class_create(THIS_MODULE, "crctl");
+	if (IS_ERR(crctl_class)) {
+		ret = PTR_ERR(crctl_class);
+		goto out_cleandev;
+	}
+
+	class_err = class_device_create(crctl_class, NULL,
+		MKDEV(CRCTL_MAJOR, 0), NULL, CRCTL_NAME);
+	if (IS_ERR(class_err)) {
+		ret = PTR_ERR(class_err);
+		goto out_rmclass;
+	}
+	goto out;
+
+out_rmclass:
+	class_destroy(crctl_class);
+out_cleandev:
+	unregister_chrdev(CRCTL_MAJOR, CRCTL_NAME);
+out:
+	return ret;
+}
+
+fs_initcall(crctl_init);
+module_exit(crctl_exit);
--- linux-2.6.19.2/fs/Makefile.original	2007-01-10 11:10:37.000000000 -0800
+++ linux-2.6.19.2/fs/Makefile	2007-01-22 15:13:59.000000000 -0800
@@ -10,7 +10,7 @@ obj-y :=	open.o read_write.o file_table.
 		ioctl.o readdir.o select.o fifo.o locks.o dcache.o inode.o \
 		attr.o bad_inode.o file.o filesystems.o namespace.o aio.o \
 		seq_file.o xattr.o libfs.o fs-writeback.o \
-		pnode.o drop_caches.o splice.o sync.o utimes.o
+		pnode.o drop_caches.o splice.o sync.o utimes.o pipe-cr-debug.o
 
 ifeq ($(CONFIG_BLOCK),y)
 obj-y +=	buffer.o bio.o block_dev.o direct-io.o mpage.o ioprio.o
-------------- next part --------------
_______________________________________________
Containers mailing list
Containers at lists.osdl.org
https://lists.osdl.org/mailman/listinfo/containers