[PATCH] uml: fix major & minor handling in hostfs

Currently hostfs passes the rdev value from stat() on the host as rdev
value to return to stat() on the guest; but we cannot pass rdev as is
because glibc and the kernel disagree about its definition.  So we must
decode it in a major/minor couple with glibc macros and re-encode it in
kernelspace code.
Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade_spam@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/hostfs/hostfs.h

@@ -38,7 +38,7 @@ extern int stat_file(const char *path, unsigned long long *inode_out,
 		     int *blksize_out, unsigned long long *blocks_out);
 extern int access_file(char *path, int r, int w, int x);
 extern int open_file(char *path, int r, int w, int append);
-extern int file_type(const char *path, int *rdev);
+extern int file_type(const char *path, int *maj, int *min);
 extern void *open_dir(char *path, int *err_out);
 extern char *read_dir(void *stream, unsigned long long *pos,
 		      unsigned long long *ino_out, int *len_out);

fs/hostfs/hostfs_kern.c

@@ -18,6 +18,7 @@
 #include <linux/buffer_head.h>
 #include <linux/root_dev.h>
 #include <linux/statfs.h>
+#include <linux/kdev_t.h>
 #include <asm/uaccess.h>
 #include "hostfs.h"
 #include "kern_util.h"
@@ -230,7 +231,7 @@ static int read_inode(struct inode *ino)
 	if(name == NULL)
 		goto out;
 
-	if(file_type(name, NULL) == OS_TYPE_SYMLINK){
+	if(file_type(name, NULL, NULL) == OS_TYPE_SYMLINK){
 		name = follow_link(name);
 		if(IS_ERR(name)){
 			err = PTR_ERR(name);
@@ -523,13 +524,17 @@ static struct address_space_operations hostfs_aops = {
 static int init_inode(struct inode *inode, struct dentry *dentry)
 {
 	char *name;
-	int type, err = -ENOMEM, rdev;
+	int type, err = -ENOMEM;
+	int maj, min;
+	dev_t rdev = 0;
 
 	if(dentry){
 		name = dentry_name(dentry, 0);
 		if(name == NULL)
 			goto out;
-		type = file_type(name, &rdev);
+		type = file_type(name, &maj, &min);
+		/*Reencode maj and min with the kernel encoding.*/
+		rdev = MKDEV(maj, min);
 		kfree(name);
 	}
 	else type = OS_TYPE_DIR;

fs/hostfs/hostfs_user.c

@@ -54,14 +54,18 @@ int stat_file(const char *path, unsigned long long *inode_out, int *mode_out,
 	return(0);
 }
 
-int file_type(const char *path, int *rdev)
+int file_type(const char *path, int *maj, int *min)
 {
  	struct stat64 buf;
 
 	if(lstat64(path, &buf) < 0)
 		return(-errno);
-	if(rdev != NULL)
-		*rdev = buf.st_rdev;
+	/*We cannot pass rdev as is because glibc and the kernel disagree
+	 *about its definition.*/
+	if(maj != NULL)
+		*maj = major(buf.st_rdev);
+	if(min != NULL)
+		*min = minor(buf.st_rdev);
 
 	if(S_ISDIR(buf.st_mode)) return(OS_TYPE_DIR);
 	else if(S_ISLNK(buf.st_mode)) return(OS_TYPE_SYMLINK);