sk: Pre-read sock packets into buffer

 criu/sk-queue.c | 33 ++++++++++++---------------------
 1 file changed, 12 insertions(+), 21 deletions(-)

In order to prepare for the use of sockets to transfer the image files
lseek calls needs to be removed. For sk-queue, we now read the packet
data at the same time than the header. This has the disadvantage to
consume more memory between the image read and the packets restore, but
should hopefully be affordable.
Signed-off-by: Rodrigo Bruno <rbruno@gsd.inesc-id.pt>
Signed-off-by: Katerina Koukiou <k.koukiou@gmail.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

criu/sk-queue.c

@@ -27,7 +27,7 @@
 struct sk_packet {
 	struct list_head	list;
 	SkPacketEntry		*entry;
-	off_t			img_off;
+	char        		*data;
 };
 
 static LIST_HEAD(packets_list);
@@ -37,14 +37,20 @@ static int collect_one_packet(void *obj, ProtobufCMessage *msg, struct cr_img *i
 	struct sk_packet *pkt = obj;
 
 	pkt->entry = pb_msg(msg, SkPacketEntry);
-	pkt->img_off = lseek(img_raw_fd(img), 0, SEEK_CUR);
+
+	pkt->data = xmalloc(pkt->entry->length);
+	if (pkt->data ==NULL)
+		return -1;
+
 	/*
 	 * NOTE: packet must be added to the tail. Otherwise sequence
 	 * will be broken.
 	 */
 	list_add_tail(&pkt->list, &packets_list);
-	if (lseek(img_raw_fd(img), pkt->entry->length, SEEK_CUR) < 0) {
-		pr_perror("Unable to change an image offset");
+
+	if (read_img_buf(img, pkt->data, pkt->entry->length) != 1) {
+		xfree(pkt->data);
+		pr_perror("Unable to read packet data");
 		return -1;
 	}
 
@@ -208,7 +214,6 @@ int restore_sk_queue(int fd, unsigned int peer_id)
 
 	list_for_each_entry_safe(pkt, tmp, &packets_list, list) {
 		SkPacketEntry *entry = pkt->entry;
-		char *buf;
 
 		if (entry->id_for != peer_id)
 			continue;
@@ -224,22 +229,8 @@ int restore_sk_queue(int fd, unsigned int peer_id)
 		 * boundaries messages should be saved.
 		 */
 
-		buf = xmalloc(entry->length);
-		if (buf ==NULL)
-			goto err;
-
-		if (lseek(img_raw_fd(img), pkt->img_off, SEEK_SET) == -1) {
-			pr_perror("lseek() failed");
-			xfree(buf);
-			goto err;
-		}
-		if (read_img_buf(img, buf, entry->length) != 1) {
-			xfree(buf);
-			goto err;
-		}
-
-		ret = write(fd, buf, entry->length);
-		xfree(buf);
+		ret = write(fd, pkt->data, entry->length);
+		xfree(pkt->data);
 		if (ret < 0) {
 			pr_perror("Failed to send packet");
 			goto err;