ghost: Add chunked ghost files

If the ghost file is too big, it might make sence to try seeking
for holes in it, thus reducing the image size.

We've seen this once for tmpfs files in issue #230.
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

criu/files-reg.c

@@ -9,9 +9,15 @@
 #include <sys/vfs.h>
 #include <sys/prctl.h>
 #include <ctype.h>
+#include <sys/sendfile.h>
 #include <sched.h>
 #include <sys/capability.h>
 
+#ifndef SEEK_DATA
+#define SEEK_DATA	3
+#define SEEK_HOLE	4
+#endif
+
 /* Stolen from kernel/fs/nfs/unlink.c */
 #define SILLYNAME_PREF ".nfs"
 #define SILLYNAME_SUFF_LEN (((unsigned)sizeof(u64) << 1) + ((unsigned)sizeof(unsigned int) << 1))
@@ -142,6 +148,115 @@ static int trim_last_parent(char *path)
 	return 0;
 }
 
+#define BUFSIZE	(4096)
+
+static int copy_chunk_from_file(int fd, int img, off_t off, size_t len)
+{
+	char *buf = NULL;
+	int ret;
+
+	while (len > 0) {
+		ret = sendfile(img, fd, &off, len);
+		if (ret <= 0) {
+			pr_perror("Can't send ghost to image");
+			return -1;
+		}
+
+		len -= ret;
+	}
+
+	xfree(buf);
+
+	return 0;
+}
+
+static int copy_file_to_chunks(int fd, struct cr_img *img, size_t file_size)
+{
+	GhostChunkEntry ce = GHOST_CHUNK_ENTRY__INIT;
+	off_t data, hole = 0;
+
+	while (hole < file_size) {
+		data = lseek(fd, hole, SEEK_DATA);
+		if (data < 0) {
+			if (errno == ENXIO)
+				/* No data */
+				break;
+			else if (hole == 0) {
+				/* No SEEK_HOLE/DATA by FS */
+				data = 0;
+				hole = file_size;
+			} else {
+				pr_perror("Can't seek file data");
+				return -1;
+			}
+		} else {
+			hole = lseek(fd, data, SEEK_HOLE);
+			if (hole < 0) {
+				pr_perror("Can't seek file hole");
+				return -1;
+			}
+		}
+
+		ce.len = hole - data;
+		ce.off = data;
+
+		if (pb_write_one(img, &ce, PB_GHOST_CHUNK))
+			return -1;
+
+		if (copy_chunk_from_file(fd, img_raw_fd(img), ce.off, ce.len))
+			return -1;
+	}
+
+	return 0;
+}
+
+static int copy_chunk_to_file(int img, int fd, off_t off, size_t len)
+{
+	char *buf = NULL;
+	int ret;
+
+	while (len > 0) {
+		if (lseek(fd, off, SEEK_SET) < 0) {
+			pr_perror("Can't seek file");
+			return -1;
+		}
+		ret = sendfile(fd, img, NULL, len);
+		if (ret < 0) {
+			pr_perror("Can't send data");
+			return -1;
+		}
+
+		off += ret;
+		len -= ret;
+	}
+
+	xfree(buf);
+
+	return 0;
+}
+
+static int copy_file_from_chunks(struct cr_img *img, int fd, size_t file_size)
+{
+	if (ftruncate(fd, file_size) < 0) {
+		pr_perror("Can't make file size");
+		return -1;
+	}
+
+	while (1) {
+		int ret;
+		GhostChunkEntry *ce;
+
+		ret = pb_read_one_eof(img, &ce, PB_GHOST_CHUNK);
+		if (ret <= 0)
+			return ret;
+
+		if (copy_chunk_to_file(img_raw_fd(img), fd, ce->off, ce->len))
+			return -1;
+
+		ghost_chunk_entry__free_unpacked(ce, NULL);
+	}
+}
+
 static int mkreg_ghost(char *path, GhostFileEntry *gfe, struct cr_img *img)
 {
 	int gfd, ret;
@@ -150,7 +265,15 @@ static int mkreg_ghost(char *path, GhostFileEntry *gfe, struct cr_img *img)
 	if (gfd < 0)
 		return -1;
 
-	ret = copy_file(img_raw_fd(img), gfd, 0);
+	if (gfe->chunks) {
+		if (!gfe->has_size) {
+			pr_err("Corrupted ghost image -> no size\n");
+			return -1;
+		}
+
+		ret = copy_file_from_chunks(img, gfd, gfe->size);
+	} else
+		ret = copy_file(img_raw_fd(img), gfd, 0);
 	if (ret < 0)
 		unlink(path);
 	close(gfd);
@@ -587,6 +710,9 @@ static struct collect_image_info remap_cinfo = {
 	.collect = collect_one_remap,
 };
 
+/* Tiny files don't need to generate chunks in ghost image. */
+#define GHOST_CHUNKS_THRESH	(3 * 4096)
+
 static int dump_ghost_file(int _fd, u32 id, const struct stat *st, dev_t phys_dev)
 {
 	struct cr_img *img;
@@ -619,6 +745,12 @@ static int dump_ghost_file(int _fd, u32 id, const struct stat *st, dev_t phys_de
 		gfe.rdev = st->st_rdev;
 	}
 
+	if (S_ISREG(st->st_mode) && (st->st_size >= GHOST_CHUNKS_THRESH)) {
+		gfe.has_chunks = gfe.chunks = true;
+		gfe.has_size = true;
+		gfe.size = st->st_size;
+	}
+
 	if (pb_write_one(img, &gfe, PB_GHOST_FILE))
 		return -1;
 
@@ -636,7 +768,11 @@ static int dump_ghost_file(int _fd, u32 id, const struct stat *st, dev_t phys_de
 			pr_perror("Can't open ghost original file");
 			return -1;
 		}
-		ret = copy_file(fd, img_raw_fd(img), st->st_size);
+
+		if (gfe.chunks)
+			ret = copy_file_to_chunks(fd, img, st->st_size);
+		else
+			ret = copy_file(fd, img_raw_fd(img), st->st_size);
 		close(fd);
 		if (ret)
 			return -1;

criu/include/protobuf-desc.h

@@ -59,6 +59,7 @@ enum {
 	PB_BINFMT_MISC,		/* 50 */
 	PB_TTY_DATA,
 	PB_AUTOFS,
+	PB_GHOST_CHUNK,
 
 	/* PB_AUTOGEN_STOP */
 

images/ghost-file.proto

@@ -13,4 +13,11 @@ message ghost_file_entry {
 	optional uint32		rdev		= 6 [(criu).dev = true, (criu).odev = true];
 	optional timeval	atim		= 7;
 	optional timeval	mtim		= 8;
+	optional bool		chunks		= 9;
+	optional uint64		size		= 10;
+}
+
+message ghost_chunk_entry {
+	required uint64		len		= 1;
+	required uint64		off		= 2;
 }