mem: Abstraction layer for putting pages into image

We'll send them over network soon, so prepare abstraction layer for
this. Shmem is not on this scheme yet.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

Makefile.crtools

@@ -41,6 +41,7 @@ obj-y	+= tty.o
 obj-y	+= cr-exec.o
 obj-y	+= file-lock.o
 obj-y	+= page-pipe.o
+obj-y	+= page-xfer.o
 
 ifneq ($(MAKECMDGOALS),clean)
 incdeps := y

include/page-xfer.h

+#ifndef __CR_PAGE_XFER__H__
+#define __CR_PAGE_XFER__H__
+struct page_xfer {
+	int (*write_pagemap)(struct page_xfer *self, struct iovec *iov, int pipe);
+	void (*close)(struct page_xfer *self);
+	int fd;
+	union {
+		int fd_pg;
+	};
+};
+
+int open_page_xfer(struct page_xfer *xfer, int fd_type, long id);
+#endif

page-xfer.c

+#include <unistd.h>
+
+#include "crtools.h"
+#include "page-xfer.h"
+
+#include "protobuf.h"
+#include "protobuf/pagemap.pb-c.h"
+
+static int write_pagemap_loc(struct page_xfer *xfer,
+		struct iovec *iov, int p)
+{
+	PagemapEntry pe = PAGEMAP_ENTRY__INIT;
+
+	pe.vaddr = encode_pointer(iov->iov_base);
+	pe.nr_pages = iov->iov_len / PAGE_SIZE;
+
+	if (pb_write_one(xfer->fd, &pe, PB_PAGEMAP) < 0)
+		return -1;
+
+	if (splice(p, NULL, xfer->fd_pg, NULL, iov->iov_len,
+				SPLICE_F_MOVE) != iov->iov_len)
+		return -1;
+
+	return 0;
+}
+
+static void close_page_xfer(struct page_xfer *xfer)
+{
+	close(xfer->fd_pg);
+	close(xfer->fd);
+}
+
+int open_page_xfer(struct page_xfer *xfer, int fd_type, long id)
+{
+	xfer->fd = open_image(fd_type, O_DUMP, id);
+	if (xfer->fd < 0)
+		return -1;
+
+	xfer->fd_pg = open_pages_image(O_DUMP, xfer->fd);
+	if (xfer->fd_pg < 0) {
+		close(xfer->fd);
+		return -1;
+	}
+
+	xfer->write_pagemap = write_pagemap_loc;
+	xfer->close = close_page_xfer;
+	return 0;
+}

parasite-syscall.c

@@ -23,6 +23,7 @@
 #include "pstree.h"
 #include "net.h"
 #include "page-pipe.h"
+#include "page-xfer.h"
 
 #include <string.h>
 #include <stdlib.h>
@@ -549,11 +550,12 @@ int parasite_dump_pages_seized(struct parasite_ctl *ctl, int vpid,
 {
 	struct parasite_dump_pages_args *args;
 	u64 *map;
-	int pagemap, fd, fd_pg;
+	int pagemap;
 	struct page_pipe *pp;
 	struct page_pipe_buf *ppb;
 	struct vma_area *vma_area;
 	int ret = -1;
+	struct page_xfer xfer;
 
 	pr_info("\n");
 	pr_info("Dumping pages (type: %d pid: %d)\n", CR_FD_PAGES, ctl->pid);
@@ -604,12 +606,9 @@ int parasite_dump_pages_seized(struct parasite_ctl *ctl, int vpid,
 		args->off += args->nr;
 	}
 
-	fd = open_image(CR_FD_PAGEMAP, O_DUMP, (long)vpid);
-	if (fd < 0)
+	ret = open_page_xfer(&xfer, CR_FD_PAGEMAP, vpid);
+	if (ret < 0)
 		goto out_pp;
-	fd_pg = open_pages_image(O_DUMP, fd);
-	if (fd_pg < 0)
-		goto out_fd;
 
 	ret = -1;
 	list_for_each_entry(ppb, &pp->bufs, l) {
@@ -618,30 +617,19 @@ int parasite_dump_pages_seized(struct parasite_ctl *ctl, int vpid,
 		pr_debug("Dump pages %d/%d\n", ppb->pages_in, ppb->nr_segs);
 
 		for (i = 0; i < ppb->nr_segs; i++) {
-			PagemapEntry pe = PAGEMAP_ENTRY__INIT;
 			struct iovec *iov = &ppb->iov[i];
 
-			pe.vaddr = encode_pointer(iov->iov_base);
-			pe.nr_pages = iov->iov_len / PAGE_SIZE;
-
 			pr_debug("\t%p [%u]\n", iov->iov_base,
 					(unsigned int)(iov->iov_len / PAGE_SIZE));
 
-			if (pb_write_one(fd, &pe, PB_PAGEMAP) < 0)
-				break;
-			if (splice(ppb->p[0], NULL, fd_pg, NULL, iov->iov_len,
-						SPLICE_F_MOVE) != iov->iov_len)
-				break;
+			if (xfer.write_pagemap(&xfer, iov, ppb->p[0]))
+				goto out_xfer;
 		}
-
-		if (i != ppb->nr_segs)
-			goto out_fds;
 	}
+
 	ret = 0;
-out_fds:
-	close(fd_pg);
-out_fd:
-	close(fd);
+out_xfer:
+	xfer.close(&xfer);
 out_pp:
 	destroy_page_pipe(pp);
 out_close: