kerndat: Transform kerndat_get_devpts_stat into general form

We will need devtmpfs as well so make it general.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

include/kerndat.h

@@ -3,6 +3,8 @@
 
 #include "asm/types.h"
 
+struct stat;
+
 /*
  * kerndat stands for "kernel data" and is a collection
  * of run-time information about current kernel
@@ -21,8 +23,14 @@ extern int tcp_max_rshare;
 extern int kern_last_cap;
 extern u64 zero_page_pfn;
 
-struct stat;
-extern struct stat *kerndat_get_devpts_stat(void);
+enum {
+	KERNDAT_FS_STAT_DEVPTS,
+	KERNDAT_FS_STAT_DEVTMPFS,
+
+	KERNDAT_FS_STAT_MAX
+};
+
+extern struct stat *kerndat_get_fs_stat(unsigned int which);
 
 extern bool memfd_is_supported;
 

kerndat.c

@@ -54,30 +54,50 @@ static int kerndat_get_shmemdev(void)
 	return 0;
 }
 
-struct stat *kerndat_get_devpts_stat()
+struct stat *kerndat_get_fs_stat(unsigned int which)
 {
-	static struct stat st = {};
+	static struct {
+		const char	*name;
+		const char	*path;
+		unsigned int	magic;
+		struct stat	st;
+	} kstat[KERNDAT_FS_STAT_MAX] = {
+		[KERNDAT_FS_STAT_DEVPTS] = {
+			.name	= "devpts",
+			.path	= "/dev/pts",
+			.magic	= DEVPTS_SUPER_MAGIC,
+		},
+		[KERNDAT_FS_STAT_DEVTMPFS] = {
+			.name	= "devtmpfs",
+			.path	= "/dev",
+			.magic	= TMPFS_MAGIC,
+		},
+	};
 	struct statfs fst;
 
-	if (st.st_dev != 0)
-		return &st;
+	if (which >= KERNDAT_FS_STAT_MAX) {
+		pr_err("Wrong fs type %u passed\n", which);
+		return NULL;
+	}
+
+	if (kstat[which].st.st_dev != 0)
+		return &kstat[which].st;
 
-	if (statfs("/dev/pts", &fst)) {
-		pr_perror("Unable to statefs /dev/pts");
+	if (statfs(kstat[which].path, &fst)) {
+		pr_perror("Unable to statefs %s", kstat[which].path);
 		return NULL;
 	}
-	if (fst.f_type != DEVPTS_SUPER_MAGIC) {
-		pr_err("devpts isn't mount on the host\n");
+	if (fst.f_type != kstat[which].magic) {
+		pr_err("%s isn't mount on the host\n", kstat[which].name);
 		return NULL;
 	}
 
-	/* The root /dev/pts is mounted w/o newinstance, isn't it? */
-	if (stat("/dev/pts", &st)) {
-		pr_perror("Unable to stat /dev/pts");
+	if (stat(kstat[which].path, &kstat[which].st)) {
+		pr_perror("Unable to stat %s", kstat[which].path);
 		return NULL;
 	}
 
-	return &st;
+	return &kstat[which].st;
 }
 
 /*

mount.c

@@ -686,7 +686,7 @@ static int devpts_parse(struct mount_info *pm)
 {
 	struct stat *host_st;
 
-	host_st = kerndat_get_devpts_stat();
+	host_st = kerndat_get_fs_stat(KERNDAT_FS_STAT_DEVPTS);
 	if (host_st == NULL)
 		return -1;