[Devel] [RFC][PATCH 2/2] pipe: checkpoint and restart entity

[Masahiko Takahashi]

[RFC][PATCH 2/2] pipe: checkpoint and restart entity

These functions actually checkpoint and restart a pipe's information
and buffer data.

Masahiko.

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--- linux-2.6.19.2/fs/pipe.c.original	2007-01-10 11:10:37.000000000 -0800
+++ linux-2.6.19.2/fs/pipe.c	2007-01-22 16:14:52.000000000 -0800
@@ -17,6 +17,8 @@
 #include <linux/highmem.h>
 #include <linux/pagemap.h>
 
+#include <linux/cr.h>
+
 #include <asm/uaccess.h>
 #include <asm/ioctls.h>
 
@@ -1029,3 +1031,129 @@ static void __exit exit_pipe_fs(void)
 
 fs_initcall(init_pipe_fs);
 module_exit(exit_pipe_fs);
+
+
+// -- checkpoint (ckpoint, in short)
+int dump_pipe(struct pipe_inode_info *pipe, struct cr_pipe *pipeimg)
+{
+	int err, i, n = pipe->nrbufs;
+	unsigned int buf = pipe->curbuf;
+	char *addr;
+	struct cr_pipe_buffer_info tmpbuf;
+
+	for  (i = 0 ; i < n ; i++) {
+		struct pipe_buffer *b = &pipe->bufs[buf];
+
+		tmpbuf.offset = b->offset;
+		tmpbuf.len = b->len;
+		tmpbuf.flags = b->flags;
+
+		err = b->ops->pin(pipe, b);
+		if (err)
+			return err;
+		addr = b->ops->map(pipe, b, 0);
+		if (copy_to_user(&pipeimg->bufs[i].buf,
+				addr + b->offset, b->len))
+			return -EFAULT;
+		b->ops->unmap(pipe, b, addr);
+
+		if (copy_to_user(&pipeimg->bufs[i].info,
+				&tmpbuf, sizeof(tmpbuf)))
+			return -EFAULT;
+
+		buf = (buf+1) & (PIPE_BUFFERS-1);
+	}
+	if (copy_to_user(&(pipeimg->nrbufs), &n, sizeof(n)))
+		return -EFAULT;
+
+	return n;
+}
+
+int ckpoint_pipe(struct file *filp, struct cr_pipe *img)
+{
+	struct inode *inode = filp->f_dentry->d_inode;
+	int r;
+
+	mutex_lock(&inode->i_mutex);
+	r = dump_pipe(inode->i_pipe, img);
+	mutex_unlock(&inode->i_mutex);
+
+	return r;
+}
+
+// --- restore
+static inline int install_specified_fd(int fd, struct file *file)
+{
+	current->files->next_fd = fd;
+	return (dupfd(file, fd) == fd);
+}
+
+int restore_pipebuf(struct pipe_inode_info *pipe, struct cr_pipe *pipeimg)
+{
+	int n;
+	unsigned int buf = 0;
+	struct page *page;
+	char *addr;
+
+	n = pipe->nrbufs = pipeimg->nrbufs;
+	while (n-- > 0) {
+		struct cr_pipe_buffer *a = &pipeimg->bufs[buf];
+		struct pipe_buffer *b = &pipe->bufs[buf];
+
+		page = alloc_page(GFP_HIGHUSER);
+		if (unlikely(!page)) {
+			return -ENOMEM;
+		}
+		addr = kmap(page);
+		if (copy_from_user(addr+a->info.offset, a->buf, a->info.len))
+			return -EFAULT;
+		kunmap(page);
+
+		b->page = page;
+		b->ops = &anon_pipe_buf_ops;
+		b->offset = a->info.offset;
+		b->len = a->info.len;
+		b->flags = a->info.flags;
+		buf = (buf+1) & (PIPE_BUFFERS-1);
+	}
+	return 0;
+}
+
+int restore_pipe(int *fd, struct cr_pipe *img)
+{
+	struct file *fw, *fr;
+	int r;
+
+	fw = create_write_pipe();
+	if (IS_ERR(fw))
+		return PTR_ERR(fw);
+
+	fr = create_read_pipe(fw);
+	if (IS_ERR(fr)) {
+		r = PTR_ERR(fr);
+		goto end;
+	}
+	r = restore_pipebuf(fr->f_dentry->d_inode->i_pipe, img);
+	if (r)
+		goto err_fr;
+
+	r = -EINVAL;
+	if (!install_specified_fd(fd[0], fr))
+		goto err_fdr;
+
+	if (!install_specified_fd(fd[1], fw))
+		goto err_fdw;
+
+	return fr->f_dentry->d_inode->i_pipe->nrbufs;
+
+
+err_fdw:
+	put_unused_fd(fd[1]);
+err_fdr:
+	put_unused_fd(fd[0]);
+err_fr:
+	put_filp(fr);
+end:
+	free_write_pipe(fw);
+	return r;
+}
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