mount: Fixup phys/virt devices dumping for ghost files

When dumping a ghost file we put real device in its header,
not the (btrfs) virtual one. This is done since we put real
devices into fsnotify images (we get them from proc). That
said on fsnotify ghost restore we don't need to do path
resolution, just devices compare.

And one more thing. When dumping device for ghost file for
_non_ btrfs case we have to convert stat dev_t into kernel
dev_t as all the other places in criu manipulate the latter
ones.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

files-reg.c

@@ -208,7 +208,7 @@ struct collect_image_info remap_cinfo = {
 	.collect = collect_one_remap,
 };
 
-static int dump_ghost_file(int _fd, u32 id, const struct stat *st)
+static int dump_ghost_file(int _fd, u32 id, const struct stat *st, dev_t phys_dev)
 {
 	int img;
 	GhostFileEntry gfe = GHOST_FILE_ENTRY__INIT;
@@ -224,7 +224,7 @@ static int dump_ghost_file(int _fd, u32 id, const struct stat *st)
 	gfe.mode = st->st_mode;
 
 	gfe.has_dev = gfe.has_ino = true;
-	gfe.dev = MKKDEV(MAJOR(st->st_dev), MINOR(st->st_dev));
+	gfe.dev = phys_dev;
 	gfe.ino = st->st_ino;
 
 	if (pb_write_one(img, &gfe, PB_GHOST_FILE))
@@ -270,7 +270,7 @@ struct file_remap *lookup_ghost_remap(u32 dev, u32 ino)
 
 	mutex_lock(ghost_file_mutex);
 	list_for_each_entry(gf, &ghost_files, list) {
-		if (gf->ino == ino && phys_stat_dev_match(gf->dev, dev, gf->remap.path)) {
+		if (gf->ino == ino && (gf->dev == dev)) {
 			gf->remap.users++;
 			mutex_unlock(ghost_file_mutex);
 			return &gf->remap;
@@ -309,7 +309,7 @@ static int dump_ghost_remap(char *path, const struct stat *st, int lfd, u32 id)
 	gf->id = ghost_file_ids++;
 	list_add_tail(&gf->list, &ghost_files);
 
-	if (dump_ghost_file(lfd, gf->id, st))
+	if (dump_ghost_file(lfd, gf->id, st, phys_dev))
 		return -1;
 
 dump_entry:

mount.c

@@ -166,7 +166,8 @@ dev_t phys_stat_resolve_dev(dev_t st_dev, const char *path)
 	 * superblock dev-id, in such case return device
 	 * obtained from mountinfo (ie subvolume0).
 	 */
-	return strcmp(m->fstype->name, "btrfs") ? st_dev : m->s_dev;
+	return strcmp(m->fstype->name, "btrfs") ?
+		MKKDEV(MAJOR(st_dev), MINOR(st_dev)) : m->s_dev;
 }
 
 bool phys_stat_dev_match(dev_t st_dev, dev_t phys_dev, const char *path)