criu: page-xfer: move code aroud

to remove forward declarations and create better grouping
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

criu/page-xfer.c

@@ -17,6 +17,8 @@
 #include "protobuf.h"
 #include "images/pagemap.pb-c.h"
 
+static int page_server_sk = -1;
+
 struct page_server_iov {
 	u32	cmd;
 	u32	nr_pages;
@@ -36,8 +38,6 @@ static void iovec2psi(struct iovec *iov, struct page_server_iov *ps)
 	ps->nr_pages = iov->iov_len / PAGE_SIZE;
 }
 
-static int open_page_local_xfer(struct page_xfer *xfer, int fd_type, long id);
-
 #define PS_IOV_ADD	1
 #define PS_IOV_HOLE	2
 #define PS_IOV_OPEN	3
@@ -65,723 +65,720 @@ static long decode_pm_id(u64 dst_id)
 	return (long)(dst_id >> PS_TYPE_BITS);
 }
 
-struct page_xfer_job {
-	u64	dst_id;
-	int	p[2];
-	unsigned pipe_size;
-	struct page_xfer loc_xfer;
-};
+/* page-server xfer */
+static int write_pagemap_to_server(struct page_xfer *xfer,
+		struct iovec *iov)
+{
+	struct page_server_iov pi;
 
-static struct page_xfer_job cxfer = {
-	.dst_id = ~0,
-};
+	pi.cmd = PS_IOV_ADD;
+	pi.dst_id = xfer->dst_id;
+	iovec2psi(iov, &pi);
 
-static void page_server_close(void)
-{
-	if (cxfer.dst_id != ~0)
-		cxfer.loc_xfer.close(&cxfer.loc_xfer);
+	if (write(xfer->sk, &pi, sizeof(pi)) != sizeof(pi)) {
+		pr_perror("Can't write pagemap to server");
+		return -1;
+	}
+
+	return 0;
 }
 
-static void close_page_xfer(struct page_xfer *xfer);
-static int page_server_open(int sk, struct page_server_iov *pi)
+static int write_pages_to_server(struct page_xfer *xfer,
+		int p, unsigned long len)
 {
-	int type;
-	long id;
-
-	type = decode_pm_type(pi->dst_id);
-	id = decode_pm_id(pi->dst_id);
-	pr_info("Opening %d/%ld\n", type, id);
-
-	page_server_close();
+	pr_debug("Splicing %lu bytes / %lu pages into socket\n", len, len / PAGE_SIZE);
 
-	if (open_page_local_xfer(&cxfer.loc_xfer, type, id))
+	if (splice(p, NULL, xfer->sk, NULL, len, SPLICE_F_MOVE) != len) {
+		pr_perror("Can't write pages to socket");
 		return -1;
+	}
 
-	cxfer.dst_id = pi->dst_id;
+	return 0;
+}
 
-	if (sk >= 0) {
-		char has_parent = !!cxfer.loc_xfer.parent;
+static int write_hole_to_server(struct page_xfer *xfer, struct iovec *iov)
+{
+	struct page_server_iov pi;
 
-		if (write(sk, &has_parent, 1) != 1) {
-			pr_perror("Unable to send reponse");
-			close_page_xfer(&cxfer.loc_xfer);
-			return -1;
-		}
+	pi.cmd = PS_IOV_HOLE;
+	pi.dst_id = xfer->dst_id;
+	iovec2psi(iov, &pi);
+
+	if (write(xfer->sk, &pi, sizeof(pi)) != sizeof(pi)) {
+		pr_perror("Can't write pagehole to server");
+		return -1;
 	}
 
 	return 0;
 }
 
-static int prep_loc_xfer(struct page_server_iov *pi)
+static void close_server_xfer(struct page_xfer *xfer)
 {
-	if (cxfer.dst_id != pi->dst_id) {
-		pr_warn("Deprecated IO w/o open\n");
-		return page_server_open(-1, pi);
-	} else
-		return 0;
+	xfer->sk = -1;
 }
 
-static int page_server_add(int sk, struct page_server_iov *pi)
+static int open_page_server_xfer(struct page_xfer *xfer, int fd_type, long id)
 {
-	size_t len;
-	struct page_xfer *lxfer = &cxfer.loc_xfer;
-	struct iovec iov;
+	struct page_server_iov pi;
+	char has_parent;
 
-	pr_debug("Adding %"PRIx64"/%u\n", pi->vaddr, pi->nr_pages);
+	xfer->sk = page_server_sk;
+	xfer->write_pagemap = write_pagemap_to_server;
+	xfer->write_pages = write_pages_to_server;
+	xfer->write_hole = write_hole_to_server;
+	xfer->close = close_server_xfer;
+	xfer->dst_id = encode_pm_id(fd_type, id);
+	xfer->parent = NULL;
 
-	if (prep_loc_xfer(pi))
-		return -1;
+	pi.cmd = PS_IOV_OPEN2;
+	pi.dst_id = xfer->dst_id;
+	pi.vaddr = 0;
+	pi.nr_pages = 0;
 
-	psi2iovec(pi, &iov);
-	if (lxfer->write_pagemap(lxfer, &iov))
+	if (write(xfer->sk, &pi, sizeof(pi)) != sizeof(pi)) {
+		pr_perror("Can't write to page server");
 		return -1;
+	}
 
-	len = iov.iov_len;
-	while (len > 0) {
-		ssize_t chunk;
-
-		chunk = len;
-		if (chunk > cxfer.pipe_size)
-			chunk = cxfer.pipe_size;
-
-		chunk = splice(sk, NULL, cxfer.p[1], NULL, chunk, SPLICE_F_MOVE | SPLICE_F_NONBLOCK);
-		if (chunk < 0) {
-			pr_perror("Can't read from socket");
-			return -1;
-		}
-
-		if (lxfer->write_pages(lxfer, cxfer.p[0], chunk))
-			return -1;
+	/* Push the command NOW */
+	tcp_nodelay(xfer->sk, true);
 
-		len -= chunk;
+	if (read(xfer->sk, &has_parent, 1) != 1) {
+		pr_perror("The page server doesn't answer");
+		return -1;
 	}
 
+	if (has_parent)
+		xfer->parent = (void *) 1; /* This is required for generate_iovs() */
+
 	return 0;
 }
 
-static int page_server_hole(int sk, struct page_server_iov *pi)
+/* local xfer */
+static int write_pagemap_loc(struct page_xfer *xfer,
+		struct iovec *iov)
 {
-	struct page_xfer *lxfer = &cxfer.loc_xfer;
-	struct iovec iov;
+	int ret;
+	PagemapEntry pe = PAGEMAP_ENTRY__INIT;
 
-	pr_debug("Adding %"PRIx64"/%u hole\n", pi->vaddr, pi->nr_pages);
+	iovec2pagemap(iov, &pe);
+	if (opts.auto_dedup && xfer->parent != NULL) {
+		ret = dedup_one_iovec(xfer->parent, iov);
+		if (ret == -1) {
+			pr_perror("Auto-deduplication failed");
+			return ret;
+		}
+	}
+	return pb_write_one(xfer->pmi, &pe, PB_PAGEMAP);
+}
 
-	if (prep_loc_xfer(pi))
-		return -1;
+static int write_pages_loc(struct page_xfer *xfer,
+		int p, unsigned long len)
+{
+	ssize_t ret;
 
-	psi2iovec(pi, &iov);
-	if (lxfer->write_hole(lxfer, &iov))
+	ret = splice(p, NULL, img_raw_fd(xfer->pi), NULL, len, SPLICE_F_MOVE);
+	if (ret == -1) {
+		pr_perror("Unable to spice data");
+		return -1;
+	}
+	if (ret != len) {
+		pr_err("Only %zu of %lu bytes have been spliced\n", ret, len);
 		return -1;
+	}
 
 	return 0;
 }
 
-static int page_server_check_parent(int sk, struct page_server_iov *pi);
-
-static int page_server_serve(int sk)
+static int check_pagehole_in_parent(struct page_read *p, struct iovec *iov)
 {
-	int ret = -1;
-	bool flushed = false;
+	int ret;
+	unsigned long off, end;
 
 	/*
-	 * This socket only accepts data except one thing -- it
-	 * writes back the has_parent bit from time to time, so
-	 * make it NODELAY all the time.
+	 * Try to find pagemap entry in parent, from which
+	 * the data will be read on restore.
+	 *
+	 * This is the optimized version of the page-by-page
+	 * read_pagemap_page routine.
 	 */
-	tcp_nodelay(sk, true);
 
-	if (pipe(cxfer.p)) {
-		pr_perror("Can't make pipe for xfer");
-		close(sk);
-		return -1;
-	}
+	pr_debug("Checking %p/%zu hole\n", iov->iov_base, iov->iov_len);
+	off = (unsigned long)iov->iov_base;
+	end = off + iov->iov_len;
+	while (1) {
+		struct iovec piov;
+		unsigned long pend;
 
-	cxfer.pipe_size = fcntl(cxfer.p[0], F_GETPIPE_SZ, 0);
-	pr_debug("Created xfer pipe size %u\n", cxfer.pipe_size);
+		ret = p->seek_page(p, off, true);
+		if (ret <= 0 || !p->pe)
+			return -1;
 
-	while (1) {
-		struct page_server_iov pi;
+		pagemap2iovec(p->pe, &piov);
+		pr_debug("\tFound %p/%zu\n", piov.iov_base, piov.iov_len);
 
-		ret = recv(sk, &pi, sizeof(pi), MSG_WAITALL);
-		if (!ret)
-			break;
+		/*
+		 * The pagemap entry in parent may heppen to be
+		 * shorter, than the hole we write. In this case
+		 * we should go ahead and check the remainder.
+		 */
 
-		if (ret != sizeof(pi)) {
-			pr_perror("Can't read pagemap from socket");
-			ret = -1;
-			break;
-		}
+		pend = (unsigned long)piov.iov_base + piov.iov_len;
+		if (end <= pend)
+			return 0;
 
-		flushed = false;
+		pr_debug("\t\tcontinue on %lx\n", pend);
+		off = pend;
+	}
+}
 
-		switch (pi.cmd) {
-		case PS_IOV_OPEN:
-			ret = page_server_open(-1, &pi);
-			break;
-		case PS_IOV_OPEN2:
-			ret = page_server_open(sk, &pi);
-			break;
-		case PS_IOV_PARENT:
-			ret = page_server_check_parent(sk, &pi);
-			break;
-		case PS_IOV_ADD:
-			ret = page_server_add(sk, &pi);
-			break;
-		case PS_IOV_HOLE:
-			ret = page_server_hole(sk, &pi);
-			break;
-		case PS_IOV_FLUSH:
-		case PS_IOV_FLUSH_N_CLOSE:
-		{
-			int32_t status = 0;
+static int write_pagehole_loc(struct page_xfer *xfer, struct iovec *iov)
+{
+	PagemapEntry pe = PAGEMAP_ENTRY__INIT;
 
-			ret = 0;
+	if (xfer->parent != NULL) {
+		int ret;
 
-			/*
-			 * An answer must be sent back to inform another side,
-			 * that all data were received
-			 */
-			if (write(sk, &status, sizeof(status)) != sizeof(status)) {
-				pr_perror("Can't send the final package");
-				ret = -1;
-			}
+		ret = check_pagehole_in_parent(xfer->parent, iov);
+		if (ret) {
+			pr_err("Hole %p/%zu not found in parent\n",
+					iov->iov_base, iov->iov_len);
+			return -1;
+		}
+	}
 
-			flushed = true;
-			break;
-		}
-		default:
-			pr_err("Unknown command %u\n", pi.cmd);
-			ret = -1;
-			break;
-		}
+	iovec2pagemap(iov, &pe);
+	pe.has_in_parent = true;
+	pe.in_parent = true;
 
-		if (ret || (pi.cmd == PS_IOV_FLUSH_N_CLOSE))
-			break;
+	if (pb_write_one(xfer->pmi, &pe, PB_PAGEMAP) < 0)
+		return -1;
+
+	return 0;
+}
+
+static void close_page_xfer(struct page_xfer *xfer)
+{
+	if (xfer->parent != NULL) {
+		xfer->parent->close(xfer->parent);
+		xfree(xfer->parent);
+		xfer->parent = NULL;
 	}
+	close_image(xfer->pi);
+	close_image(xfer->pmi);
+}
 
-	if (!ret && !flushed) {
-		pr_err("The data were not flushed\n");
-		ret = -1;
+static int open_page_local_xfer(struct page_xfer *xfer, int fd_type, long id)
+{
+	xfer->pmi = open_image(fd_type, O_DUMP, id);
+	if (!xfer->pmi)
+		return -1;
+
+	xfer->pi = open_pages_image(O_DUMP, xfer->pmi);
+	if (!xfer->pi) {
+		close_image(xfer->pmi);
+		return -1;
 	}
 
-	if (ret == 0 && opts.ps_socket == -1) {
-		char c;
+	/*
+	 * Open page-read for parent images (if it exists). It will
+	 * be used for two things:
+	 * 1) when writing a page, those from parent will be dedup-ed
+	 * 2) when writing a hole, the respective place would be checked
+	 *    to exist in parent (either pagemap or hole)
+	 */
+	xfer->parent = NULL;
+	if (fd_type == CR_FD_PAGEMAP) {
+		int ret;
+		int pfd;
 
-		/*
-		 * Wait when a remote side closes the connection
-		 * to avoid TIME_WAIT bucket
-		 */
+		pfd = openat(get_service_fd(IMG_FD_OFF), CR_PARENT_LINK, O_RDONLY);
+		if (pfd < 0 && errno == ENOENT)
+			goto out;
 
-		if (read(sk, &c, sizeof(c)) != 0) {
-			pr_perror("Unexpected data");
-			ret = -1;
+		xfer->parent = xmalloc(sizeof(*xfer->parent));
+		if (!xfer->parent) {
+			close(pfd);
+			return -1;
+		}
+
+		ret = open_page_read_at(pfd, id, xfer->parent, PR_TASK);
+		if (ret <= 0) {
+			pr_perror("No parent image found, though parent directory is set");
+			xfree(xfer->parent);
+			xfer->parent = NULL;
+			close(pfd);
+			goto out;
 		}
+		close(pfd);
 	}
 
-	page_server_close();
-	pr_info("Session over\n");
+out:
+	xfer->write_pagemap = write_pagemap_loc;
+	xfer->write_pages = write_pages_loc;
+	xfer->write_hole = write_pagehole_loc;
+	xfer->close = close_page_xfer;
+	return 0;
+}
 
-	close(sk);
-	return ret;
+int open_page_xfer(struct page_xfer *xfer, int fd_type, long id)
+{
+	if (opts.use_page_server)
+		return open_page_server_xfer(xfer, fd_type, id);
+	else
+		return open_page_local_xfer(xfer, fd_type, id);
 }
 
-int cr_page_server(bool daemon_mode, int cfd)
+int page_xfer_dump_pages(struct page_xfer *xfer, struct page_pipe *pp,
+		unsigned long off)
 {
-	int ask = -1;
-	int sk = -1;
-	int ret;
+	struct page_pipe_buf *ppb;
+	struct iovec *hole = NULL;
 
-	up_page_ids_base();
+	pr_debug("Transfering pages:\n");
 
-	if (opts.ps_socket != -1) {
-		ret = 0;
-		ask = opts.ps_socket;
-		pr_info("Re-using ps socket %d\n", ask);
-		goto no_server;
-	}
+	if (pp->free_hole)
+		hole = &pp->holes[0];
 
-	sk = setup_tcp_server("page");
-	if (sk == -1)
-		return -1;
-no_server:
-	ret = run_tcp_server(daemon_mode, &ask, cfd, sk);
-	if (ret != 0)
-		return ret;
+	list_for_each_entry(ppb, &pp->bufs, l) {
+		int i;
 
-	if (ask >= 0)
-		ret = page_server_serve(ask);
+		pr_debug("\tbuf %d/%d\n", ppb->pages_in, ppb->nr_segs);
 
-	if (daemon_mode)
-		exit(ret);
+		for (i = 0; i < ppb->nr_segs; i++) {
+			struct iovec *iov = &ppb->iov[i];
 
-	return ret;
+			while (hole && (hole->iov_base < iov->iov_base)) {
+				BUG_ON(hole->iov_base < (void *)off);
+				hole->iov_base -= off;
+				pr_debug("\th %p [%u]\n", hole->iov_base,
+						(unsigned int)(hole->iov_len / PAGE_SIZE));
+				if (xfer->write_hole(xfer, hole))
+					return -1;
 
-}
+				hole++;
+				if (hole >= &pp->holes[pp->free_hole])
+					hole = NULL;
+			}
 
-static int page_server_sk = -1;
+			BUG_ON(iov->iov_base < (void *)off);
+			iov->iov_base -= off;
+			pr_debug("\tp %p [%u]\n", iov->iov_base,
+					(unsigned int)(iov->iov_len / PAGE_SIZE));
 
-int connect_to_page_server(void)
-{
-	if (!opts.use_page_server)
-		return 0;
+			if (xfer->write_pagemap(xfer, iov))
+				return -1;
+			if (xfer->write_pages(xfer, ppb->p[0], iov->iov_len))
+				return -1;
+		}
+	}
 
-	if (opts.ps_socket != -1) {
-		page_server_sk = opts.ps_socket;
-		pr_info("Re-using ps socket %d\n", page_server_sk);
-		goto out;
+	while (hole) {
+		BUG_ON(hole->iov_base < (void *)off);
+		hole->iov_base -= off;
+		pr_debug("\th* %p [%u]\n", hole->iov_base,
+				(unsigned int)(hole->iov_len / PAGE_SIZE));
+		if (xfer->write_hole(xfer, hole))
+			return -1;
+
+		hole++;
+		if (hole >= &pp->holes[pp->free_hole])
+			hole = NULL;
 	}
 
-	page_server_sk = setup_tcp_client(opts.addr);
-	if (page_server_sk == -1)
-		return -1;
-out:
-	/*
-	 * CORK the socket at the very beginning. As per ANK
-	 * the corked by default socket with sporadic NODELAY-s
-	 * on urgent data is the smartest mode ever.
-	 */
-	tcp_cork(page_server_sk, true);
 	return 0;
 }
 
-int disconnect_from_page_server(void)
+/*
+ * Return:
+ *	 1 - if a parent image exists
+ *	 0 - if a parent image doesn't exist
+ *	-1 - in error cases
+ */
+int check_parent_local_xfer(int fd_type, int id)
 {
-	struct page_server_iov pi = { };
-	int32_t status = -1;
-	int ret = -1;
-
-	if (!opts.use_page_server)
-		return 0;
+	char path[PATH_MAX];
+	struct stat st;
+	int ret, pfd;
 
-	if (page_server_sk == -1)
+	pfd = openat(get_service_fd(IMG_FD_OFF), CR_PARENT_LINK, O_RDONLY);
+	if (pfd < 0 && errno == ENOENT)
 		return 0;
 
-	pr_info("Disconnect from the page server %s:%u\n",
-			opts.addr, (int)ntohs(opts.port));
-
-	if (opts.ps_socket != -1)
-		/*
-		 * The socket might not get closed (held by
-		 * the parent process) so we must order the
-		 * page-server to terminate itself.
-		 */
-		pi.cmd = PS_IOV_FLUSH_N_CLOSE;
-	else
-		pi.cmd = PS_IOV_FLUSH;
-
-	if (write(page_server_sk, &pi, sizeof(pi)) != sizeof(pi)) {
-		pr_perror("Can't write the fini command to server");
-		goto out;
-	}
-
-	if (read(page_server_sk, &status, sizeof(status)) != sizeof(status)) {
-		pr_perror("The page server doesn't answer");
-		goto out;
+	snprintf(path, sizeof(path), imgset_template[fd_type].fmt, id);
+	ret = fstatat(pfd, path, &st, 0);
+	if (ret == -1 && errno != ENOENT) {
+		pr_perror("Unable to stat %s", path);
+		close(pfd);
+		return -1;
 	}
 
-	ret = 0;
-out:
-	close_safe(&page_server_sk);
-	return ret ? : status;
+	close(pfd);
+	return (ret == 0);
 }
 
-static int write_pagemap_to_server(struct page_xfer *xfer,
-		struct iovec *iov)
+/* page server */
+static int page_server_check_parent(int sk, struct page_server_iov *pi)
 {
-	struct page_server_iov pi;
+	int type, ret;
+	long id;
 
-	pi.cmd = PS_IOV_ADD;
-	pi.dst_id = xfer->dst_id;
-	iovec2psi(iov, &pi);
+	type = decode_pm_type(pi->dst_id);
+	id = decode_pm_id(pi->dst_id);
 
-	if (write(xfer->sk, &pi, sizeof(pi)) != sizeof(pi)) {
-		pr_perror("Can't write pagemap to server");
+	ret = check_parent_local_xfer(type, id);
+	if (ret < 0)
+		return -1;
+
+	if (write(sk, &ret, sizeof(ret)) != sizeof(ret)) {
+		pr_perror("Unable to send reponse");
 		return -1;
 	}
 
 	return 0;
 }
 
-static int write_pages_to_server(struct page_xfer *xfer,
-		int p, unsigned long len)
+static int check_parent_server_xfer(int fd_type, long id)
 {
-	pr_debug("Splicing %lu bytes / %lu pages into socket\n", len, len / PAGE_SIZE);
+	struct page_server_iov pi = {};
+	int has_parent;
 
-	if (splice(p, NULL, xfer->sk, NULL, len, SPLICE_F_MOVE) != len) {
-		pr_perror("Can't write pages to socket");
+	pi.cmd = PS_IOV_PARENT;
+	pi.dst_id = encode_pm_id(fd_type, id);
+
+	if (write(page_server_sk, &pi, sizeof(pi)) != sizeof(pi)) {
+		pr_perror("Can't write to page server");
 		return -1;
 	}
 
-	return 0;
-}
-
-static int write_hole_to_server(struct page_xfer *xfer, struct iovec *iov)
-{
-	struct page_server_iov pi;
-
-	pi.cmd = PS_IOV_HOLE;
-	pi.dst_id = xfer->dst_id;
-	iovec2psi(iov, &pi);
+	tcp_nodelay(page_server_sk, true);
 
-	if (write(xfer->sk, &pi, sizeof(pi)) != sizeof(pi)) {
-		pr_perror("Can't write pagehole to server");
+	if (read(page_server_sk, &has_parent, sizeof(int)) != sizeof(int)) {
+		pr_perror("The page server doesn't answer");
 		return -1;
 	}
 
-	return 0;
+	return has_parent;
 }
 
-static void close_server_xfer(struct page_xfer *xfer)
+int check_parent_page_xfer(int fd_type, long id)
 {
-	xfer->sk = -1;
+	if (opts.use_page_server)
+		return check_parent_server_xfer(fd_type, id);
+	else
+		return check_parent_local_xfer(fd_type, id);
 }
 
-static int open_page_server_xfer(struct page_xfer *xfer, int fd_type, long id)
+struct page_xfer_job {
+	u64	dst_id;
+	int	p[2];
+	unsigned pipe_size;
+	struct page_xfer loc_xfer;
+};
+
+static struct page_xfer_job cxfer = {
+	.dst_id = ~0,
+};
+
+static void page_server_close(void)
 {
-	struct page_server_iov pi;
-	char has_parent;
+	if (cxfer.dst_id != ~0)
+		cxfer.loc_xfer.close(&cxfer.loc_xfer);
+}
 
-	xfer->sk = page_server_sk;
-	xfer->write_pagemap = write_pagemap_to_server;
-	xfer->write_pages = write_pages_to_server;
-	xfer->write_hole = write_hole_to_server;
-	xfer->close = close_server_xfer;
-	xfer->dst_id = encode_pm_id(fd_type, id);
-	xfer->parent = NULL;
+static int page_server_open(int sk, struct page_server_iov *pi)
+{
+	int type;
+	long id;
 
-	pi.cmd = PS_IOV_OPEN2;
-	pi.dst_id = xfer->dst_id;
-	pi.vaddr = 0;
-	pi.nr_pages = 0;
+	type = decode_pm_type(pi->dst_id);
+	id = decode_pm_id(pi->dst_id);
+	pr_info("Opening %d/%ld\n", type, id);
 
-	if (write(xfer->sk, &pi, sizeof(pi)) != sizeof(pi)) {
-		pr_perror("Can't write to page server");
+	page_server_close();
+
+	if (open_page_local_xfer(&cxfer.loc_xfer, type, id))
 		return -1;
-	}
 
-	/* Push the command NOW */
-	tcp_nodelay(xfer->sk, true);
+	cxfer.dst_id = pi->dst_id;
 
-	if (read(xfer->sk, &has_parent, 1) != 1) {
-		pr_perror("The page server doesn't answer");
-		return -1;
-	}
+	if (sk >= 0) {
+		char has_parent = !!cxfer.loc_xfer.parent;
 
-	if (has_parent)
-		xfer->parent = (void *) 1; /* This is required for generate_iovs() */
+		if (write(sk, &has_parent, 1) != 1) {
+			pr_perror("Unable to send reponse");
+			close_page_xfer(&cxfer.loc_xfer);
+			return -1;
+		}
+	}
 
 	return 0;
 }
 
-static int write_pagemap_loc(struct page_xfer *xfer,
-		struct iovec *iov)
+static int prep_loc_xfer(struct page_server_iov *pi)
 {
-	int ret;
-	PagemapEntry pe = PAGEMAP_ENTRY__INIT;
-
-	iovec2pagemap(iov, &pe);
-	if (opts.auto_dedup && xfer->parent != NULL) {
-		ret = dedup_one_iovec(xfer->parent, iov);
-		if (ret == -1) {
-			pr_perror("Auto-deduplication failed");
-			return ret;
-		}
-	}
-	return pb_write_one(xfer->pmi, &pe, PB_PAGEMAP);
+	if (cxfer.dst_id != pi->dst_id) {
+		pr_warn("Deprecated IO w/o open\n");
+		return page_server_open(-1, pi);
+	} else
+		return 0;
 }
 
-static int write_pages_loc(struct page_xfer *xfer,
-		int p, unsigned long len)
+static int page_server_add(int sk, struct page_server_iov *pi)
 {
-	ssize_t ret;
+	size_t len;
+	struct page_xfer *lxfer = &cxfer.loc_xfer;
+	struct iovec iov;
 
-	ret = splice(p, NULL, img_raw_fd(xfer->pi), NULL, len, SPLICE_F_MOVE);
-	if (ret == -1) {
-		pr_perror("Unable to spice data");
-		return -1;
-	}
-	if (ret != len) {
-		pr_err("Only %zu of %lu bytes have been spliced\n", ret, len);
-		return -1;
-	}
+	pr_debug("Adding %"PRIx64"/%u\n", pi->vaddr, pi->nr_pages);
 
-	return 0;
-}
+	if (prep_loc_xfer(pi))
+		return -1;
 
-static int check_pagehole_in_parent(struct page_read *p, struct iovec *iov)
-{
-	int ret;
-	unsigned long off, end;
+	psi2iovec(pi, &iov);
+	if (lxfer->write_pagemap(lxfer, &iov))
+		return -1;
 
-	/*
-	 * Try to find pagemap entry in parent, from which
-	 * the data will be read on restore.
-	 *
-	 * This is the optimized version of the page-by-page
-	 * read_pagemap_page routine.
-	 */
+	len = iov.iov_len;
+	while (len > 0) {
+		ssize_t chunk;
 
-	pr_debug("Checking %p/%zu hole\n", iov->iov_base, iov->iov_len);
-	off = (unsigned long)iov->iov_base;
-	end = off + iov->iov_len;
-	while (1) {
-		struct iovec piov;
-		unsigned long pend;
+		chunk = len;
+		if (chunk > cxfer.pipe_size)
+			chunk = cxfer.pipe_size;
 
-		ret = p->seek_page(p, off, true);
-		if (ret <= 0 || !p->pe)
+		chunk = splice(sk, NULL, cxfer.p[1], NULL, chunk, SPLICE_F_MOVE | SPLICE_F_NONBLOCK);
+		if (chunk < 0) {
+			pr_perror("Can't read from socket");
 			return -1;
+		}
 
-		pagemap2iovec(p->pe, &piov);
-		pr_debug("\tFound %p/%zu\n", piov.iov_base, piov.iov_len);
-
-		/*
-		 * The pagemap entry in parent may heppen to be
-		 * shorter, than the hole we write. In this case
-		 * we should go ahead and check the remainder.
-		 */
-
-		pend = (unsigned long)piov.iov_base + piov.iov_len;
-		if (end <= pend)
-			return 0;
+		if (lxfer->write_pages(lxfer, cxfer.p[0], chunk))
+			return -1;
 
-		pr_debug("\t\tcontinue on %lx\n", pend);
-		off = pend;
+		len -= chunk;
 	}
+
+	return 0;
 }
 
-static int write_pagehole_loc(struct page_xfer *xfer, struct iovec *iov)
+static int page_server_hole(int sk, struct page_server_iov *pi)
 {
-	PagemapEntry pe = PAGEMAP_ENTRY__INIT;
-
-	if (xfer->parent != NULL) {
-		int ret;
+	struct page_xfer *lxfer = &cxfer.loc_xfer;
+	struct iovec iov;
 
-		ret = check_pagehole_in_parent(xfer->parent, iov);
-		if (ret) {
-			pr_err("Hole %p/%zu not found in parent\n",
-					iov->iov_base, iov->iov_len);
-			return -1;
-		}
-	}
+	pr_debug("Adding %"PRIx64"/%u hole\n", pi->vaddr, pi->nr_pages);
 
-	iovec2pagemap(iov, &pe);
-	pe.has_in_parent = true;
-	pe.in_parent = true;
+	if (prep_loc_xfer(pi))
+		return -1;
 
-	if (pb_write_one(xfer->pmi, &pe, PB_PAGEMAP) < 0)
+	psi2iovec(pi, &iov);
+	if (lxfer->write_hole(lxfer, &iov))
 		return -1;
 
 	return 0;
 }
 
-static void close_page_xfer(struct page_xfer *xfer)
-{
-	if (xfer->parent != NULL) {
-		xfer->parent->close(xfer->parent);
-		xfree(xfer->parent);
-		xfer->parent = NULL;
-	}
-	close_image(xfer->pi);
-	close_image(xfer->pmi);
-}
-
-int page_xfer_dump_pages(struct page_xfer *xfer, struct page_pipe *pp,
-		unsigned long off)
+static int page_server_serve(int sk)
 {
-	struct page_pipe_buf *ppb;
-	struct iovec *hole = NULL;
+	int ret = -1;
+	bool flushed = false;
 
-	pr_debug("Transfering pages:\n");
+	/*
+	 * This socket only accepts data except one thing -- it
+	 * writes back the has_parent bit from time to time, so
+	 * make it NODELAY all the time.
+	 */
+	tcp_nodelay(sk, true);
 
-	if (pp->free_hole)
-		hole = &pp->holes[0];
+	if (pipe(cxfer.p)) {
+		pr_perror("Can't make pipe for xfer");
+		close(sk);
+		return -1;
+	}
 
-	list_for_each_entry(ppb, &pp->bufs, l) {
-		int i;
+	cxfer.pipe_size = fcntl(cxfer.p[0], F_GETPIPE_SZ, 0);
+	pr_debug("Created xfer pipe size %u\n", cxfer.pipe_size);
 
-		pr_debug("\tbuf %d/%d\n", ppb->pages_in, ppb->nr_segs);
+	while (1) {
+		struct page_server_iov pi;
 
-		for (i = 0; i < ppb->nr_segs; i++) {
-			struct iovec *iov = &ppb->iov[i];
+		ret = recv(sk, &pi, sizeof(pi), MSG_WAITALL);
+		if (!ret)
+			break;
 
-			while (hole && (hole->iov_base < iov->iov_base)) {
-				BUG_ON(hole->iov_base < (void *)off);
-				hole->iov_base -= off;
-				pr_debug("\th %p [%u]\n", hole->iov_base,
-						(unsigned int)(hole->iov_len / PAGE_SIZE));
-				if (xfer->write_hole(xfer, hole))
-					return -1;
-
-				hole++;
-				if (hole >= &pp->holes[pp->free_hole])
-					hole = NULL;
-			}
-
-			BUG_ON(iov->iov_base < (void *)off);
-			iov->iov_base -= off;
-			pr_debug("\tp %p [%u]\n", iov->iov_base,
-					(unsigned int)(iov->iov_len / PAGE_SIZE));
-
-			if (xfer->write_pagemap(xfer, iov))
-				return -1;
-			if (xfer->write_pages(xfer, ppb->p[0], iov->iov_len))
-				return -1;
+		if (ret != sizeof(pi)) {
+			pr_perror("Can't read pagemap from socket");
+			ret = -1;
+			break;
 		}
-	}
 
-	while (hole) {
-		BUG_ON(hole->iov_base < (void *)off);
-		hole->iov_base -= off;
-		pr_debug("\th* %p [%u]\n", hole->iov_base,
-				(unsigned int)(hole->iov_len / PAGE_SIZE));
-		if (xfer->write_hole(xfer, hole))
-			return -1;
+		flushed = false;
 
-		hole++;
-		if (hole >= &pp->holes[pp->free_hole])
-			hole = NULL;
-	}
+		switch (pi.cmd) {
+		case PS_IOV_OPEN:
+			ret = page_server_open(-1, &pi);
+			break;
+		case PS_IOV_OPEN2:
+			ret = page_server_open(sk, &pi);
+			break;
+		case PS_IOV_PARENT:
+			ret = page_server_check_parent(sk, &pi);
+			break;
+		case PS_IOV_ADD:
+			ret = page_server_add(sk, &pi);
+			break;
+		case PS_IOV_HOLE:
+			ret = page_server_hole(sk, &pi);
+			break;
+		case PS_IOV_FLUSH:
+		case PS_IOV_FLUSH_N_CLOSE:
+		{
+			int32_t status = 0;
 
-	return 0;
-}
+			ret = 0;
 
-static int open_page_local_xfer(struct page_xfer *xfer, int fd_type, long id)
-{
-	xfer->pmi = open_image(fd_type, O_DUMP, id);
-	if (!xfer->pmi)
-		return -1;
+			/*
+			 * An answer must be sent back to inform another side,
+			 * that all data were received
+			 */
+			if (write(sk, &status, sizeof(status)) != sizeof(status)) {
+				pr_perror("Can't send the final package");
+				ret = -1;
+			}
 
-	xfer->pi = open_pages_image(O_DUMP, xfer->pmi);
-	if (!xfer->pi) {
-		close_image(xfer->pmi);
-		return -1;
+			flushed = true;
+			break;
+		}
+		default:
+			pr_err("Unknown command %u\n", pi.cmd);
+			ret = -1;
+			break;
+		}
+
+		if (ret || (pi.cmd == PS_IOV_FLUSH_N_CLOSE))
+			break;
 	}
 
-	/*
-	 * Open page-read for parent images (if it exists). It will
-	 * be used for two things:
-	 * 1) when writing a page, those from parent will be dedup-ed
-	 * 2) when writing a hole, the respective place would be checked
-	 *    to exist in parent (either pagemap or hole)
-	 */
-	xfer->parent = NULL;
-	if (fd_type == CR_FD_PAGEMAP) {
-		int ret;
-		int pfd;
+	if (!ret && !flushed) {
+		pr_err("The data were not flushed\n");
+		ret = -1;
+	}
 
-		pfd = openat(get_service_fd(IMG_FD_OFF), CR_PARENT_LINK, O_RDONLY);
-		if (pfd < 0 && errno == ENOENT)
-			goto out;
+	if (ret == 0 && opts.ps_socket == -1) {
+		char c;
 
-		xfer->parent = xmalloc(sizeof(*xfer->parent));
-		if (!xfer->parent) {
-			close(pfd);
-			return -1;
-		}
+		/*
+		 * Wait when a remote side closes the connection
+		 * to avoid TIME_WAIT bucket
+		 */
 
-		ret = open_page_read_at(pfd, id, xfer->parent, PR_TASK);
-		if (ret <= 0) {
-			pr_perror("No parent image found, though parent directory is set");
-			xfree(xfer->parent);
-			xfer->parent = NULL;
-			close(pfd);
-			goto out;
+		if (read(sk, &c, sizeof(c)) != 0) {
+			pr_perror("Unexpected data");
+			ret = -1;
 		}
-		close(pfd);
 	}
 
-out:
-	xfer->write_pagemap = write_pagemap_loc;
-	xfer->write_pages = write_pages_loc;
-	xfer->write_hole = write_pagehole_loc;
-	xfer->close = close_page_xfer;
-	return 0;
-}
+	page_server_close();
+	pr_info("Session over\n");
 
-int open_page_xfer(struct page_xfer *xfer, int fd_type, long id)
-{
-	if (opts.use_page_server)
-		return open_page_server_xfer(xfer, fd_type, id);
-	else
-		return open_page_local_xfer(xfer, fd_type, id);
+	close(sk);
+	return ret;
 }
 
-/*
- * Return:
- *	 1 - if a parent image exists
- *	 0 - if a parent image doesn't exist
- *	-1 - in error cases
- */
-int check_parent_local_xfer(int fd_type, int id)
+int cr_page_server(bool daemon_mode, int cfd)
 {
-	char path[PATH_MAX];
-	struct stat st;
-	int ret, pfd;
+	int ask = -1;
+	int sk = -1;
+	int ret;
 
-	pfd = openat(get_service_fd(IMG_FD_OFF), CR_PARENT_LINK, O_RDONLY);
-	if (pfd < 0 && errno == ENOENT)
-		return 0;
+	up_page_ids_base();
 
-	snprintf(path, sizeof(path), imgset_template[fd_type].fmt, id);
-	ret = fstatat(pfd, path, &st, 0);
-	if (ret == -1 && errno != ENOENT) {
-		pr_perror("Unable to stat %s", path);
-		close(pfd);
-		return -1;
+	if (opts.ps_socket != -1) {
+		ret = 0;
+		ask = opts.ps_socket;
+		pr_info("Re-using ps socket %d\n", ask);
+		goto no_server;
 	}
 
-	close(pfd);
-	return (ret == 0);
-}
+	sk = setup_tcp_server("page");
+	if (sk == -1)
+		return -1;
+no_server:
+	ret = run_tcp_server(daemon_mode, &ask, cfd, sk);
+	if (ret != 0)
+		return ret;
 
-static int page_server_check_parent(int sk, struct page_server_iov *pi)
-{
-	int type, ret;
-	long id;
+	if (ask >= 0)
+		ret = page_server_serve(ask);
 
-	type = decode_pm_type(pi->dst_id);
-	id = decode_pm_id(pi->dst_id);
+	if (daemon_mode)
+		exit(ret);
 
-	ret = check_parent_local_xfer(type, id);
-	if (ret < 0)
-		return -1;
+	return ret;
+}
 
-	if (write(sk, &ret, sizeof(ret)) != sizeof(ret)) {
-		pr_perror("Unable to send reponse");
-		return -1;
+int connect_to_page_server(void)
+{
+	if (!opts.use_page_server)
+		return 0;
+
+	if (opts.ps_socket != -1) {
+		page_server_sk = opts.ps_socket;
+		pr_info("Re-using ps socket %d\n", page_server_sk);
+		goto out;
 	}
 
+	page_server_sk = setup_tcp_client(opts.addr);
+	if (page_server_sk == -1)
+		return -1;
+out:
+	/*
+	 * CORK the socket at the very beginning. As per ANK
+	 * the corked by default socket with sporadic NODELAY-s
+	 * on urgent data is the smartest mode ever.
+	 */
+	tcp_cork(page_server_sk, true);
 	return 0;
 }
 
-static int check_parent_server_xfer(int fd_type, long id)
+int disconnect_from_page_server(void)
 {
-	struct page_server_iov pi = {};
-	int has_parent;
+	struct page_server_iov pi = { };
+	int32_t status = -1;
+	int ret = -1;
 
-	pi.cmd = PS_IOV_PARENT;
-	pi.dst_id = encode_pm_id(fd_type, id);
+	if (!opts.use_page_server)
+		return 0;
+
+	if (page_server_sk == -1)
+		return 0;
+
+	pr_info("Disconnect from the page server %s:%u\n",
+			opts.addr, (int)ntohs(opts.port));
+
+	if (opts.ps_socket != -1)
+		/*
+		 * The socket might not get closed (held by
+		 * the parent process) so we must order the
+		 * page-server to terminate itself.
+		 */
+		pi.cmd = PS_IOV_FLUSH_N_CLOSE;
+	else
+		pi.cmd = PS_IOV_FLUSH;
 
 	if (write(page_server_sk, &pi, sizeof(pi)) != sizeof(pi)) {
-		pr_perror("Can't write to page server");
-		return -1;
+		pr_perror("Can't write the fini command to server");
+		goto out;
 	}
 
-	tcp_nodelay(page_server_sk, true);
-
-	if (read(page_server_sk, &has_parent, sizeof(int)) != sizeof(int)) {
+	if (read(page_server_sk, &status, sizeof(status)) != sizeof(status)) {
 		pr_perror("The page server doesn't answer");
-		return -1;
+		goto out;
 	}
 
-	return has_parent;
-}
-
-int check_parent_page_xfer(int fd_type, long id)
-{
-	if (opts.use_page_server)
-		return check_parent_server_xfer(fd_type, id);
-	else
-		return check_parent_local_xfer(fd_type, id);
+	ret = 0;
+out:
+	close_safe(&page_server_sk);
+	return ret ? : status;
 }