mount: Config-out virtualized binfmt_misc

The need to mess with binfmt_misc super-blocks only exists
in OpenVZ kernel and troubes all the other users. So make
this code get compiled-out by default.

In VZ-builds the BINFMT_MISC_VIRTUALIZED should be put into
.config file before running make.

https://github.com/xemul/criu/issues/235
travis-ci: success for Don't compile in binfmt_misc dumping code by default (rev3)
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>
Reviewed-by: Dmirty Safonov <dsafonov@virtuozzo.com>

criu/filesystems.c

@@ -30,6 +30,7 @@ static int attach_option(struct mount_info *pm, char *opt)
 	return pm->options ? 0 : -1;
 }
 
+#ifdef CONFIG_BINFMT_MISC_VIRTUALIZED
 struct binfmt_misc_info {
 	BinfmtMiscEntry *bme;
 	struct list_head list;
@@ -370,6 +371,11 @@ int collect_binfmt_misc(void)
 {
 	return collect_image(&binfmt_misc_cinfo);
 }
+#else
+#define binfmt_misc_dump	NULL
+#define binfmt_misc_restore	NULL
+#define binfmt_misc_parse	NULL
+#endif
 
 static int tmpfs_dump(struct mount_info *pm)
 {

criu/include/cr_options.h

@@ -96,7 +96,9 @@ struct cr_options {
 	bool			enable_external_masters;
 	bool			aufs;		/* auto-deteced, not via cli */
 	bool			overlayfs;
+#ifdef CONFIG_BINFMT_MISC_VIRTUALIZED
 	bool			has_binfmt_misc; /* auto-detected */
+#endif
 	size_t			ghost_limit;
 	struct list_head	irmap_scan_paths;
 	bool			lsm_supplied;

criu/include/mount.h

@@ -71,7 +71,11 @@ struct mount_info {
 
 extern struct mount_info *mntinfo;
 extern struct ns_desc mnt_ns_desc;
+#ifdef CONFIG_BINFMT_MISC_VIRTUALIZED
 extern int collect_binfmt_misc(void);
+#else
+static inline int collect_binfmt_misc(void) { return 0; }
+#endif
 
 extern struct mount_info *mnt_entry_alloc();
 extern void mnt_entry_free(struct mount_info *mi);

criu/mount.c

@@ -1138,7 +1138,7 @@ out:
 	return -1;
 }
 
-static int add_cr_time_mount(struct mount_info *root, char *fsname, const char *path, unsigned int s_dev)
+static __maybe_unused int add_cr_time_mount(struct mount_info *root, char *fsname, const char *path, unsigned int s_dev)
 {
 	struct mount_info *mi, *t, *parent;
 
@@ -1186,7 +1186,7 @@ static int add_cr_time_mount(struct mount_info *root, char *fsname, const char *
 }
 
 /* Returns 1 in case of success, -errno in case of mount fail, and 0 on other errors */
-static int mount_cr_time_mount(struct ns_id *ns, unsigned int *s_dev, const char *source,
+static __maybe_unused int mount_cr_time_mount(struct ns_id *ns, unsigned int *s_dev, const char *source,
 			       const char *target, const char *type)
 {
 	int mnt_fd, ret, exit_code = 0;
@@ -2453,8 +2453,10 @@ static int collect_mnt_from_image(struct mount_info **pms, struct ns_id *nsid)
 			goto err;
 		}
 
+#ifdef CONFIG_BINFMT_MISC_VIRTUALIZED
 		if (me->fstype == FSTYPE__BINFMT_MISC)
 			opts.has_binfmt_misc = true;
+#endif
 
 		/* FIXME: abort unsupported early */
 		pm->fstype = decode_fstype(me->fstype);
@@ -2665,12 +2667,14 @@ static int populate_mnt_ns(void)
 	if (!pms)
 		return -1;
 
+#ifdef CONFIG_BINFMT_MISC_VIRTUALIZED
 	if (!opts.has_binfmt_misc && !list_empty(&binfmt_misc_list)) {
 		/* Add to mount tree. Generic code will mount it later */
 		ret = add_cr_time_mount(pms, "binfmt_misc", BINFMT_MISC_HOME, 0);
 		if (ret)
 			return -1;
 	}
+#endif
 
 	if (resolve_shared_mounts(mntinfo, pms->master_id))
 		return -1;
@@ -3126,6 +3130,7 @@ int collect_mnt_namespaces(bool for_dump)
 	if (ret)
 		goto err;
 
+#ifdef CONFIG_BINFMT_MISC_VIRTUALIZED
 	if (for_dump && !opts.has_binfmt_misc) {
 		unsigned int s_dev = 0;
 		struct ns_id *ns;
@@ -3153,6 +3158,7 @@ int collect_mnt_namespaces(bool for_dump)
 			}
 		}
 	}
+#endif
 
 	ret = resolve_external_mounts(mntinfo);
 	if (ret)