shuffle fs.c in bottom-up order

defs.h

@@ -120,7 +120,6 @@ void bwrite(struct buf*, uint);
 void brelse(struct buf*);
 
 // fs.c
-extern uint rootdev;
 void iinit(void);
 struct inode* iget(uint, uint);
 void ilock(struct inode*);
@@ -138,6 +137,7 @@ struct inode* mknod1(struct inode*, char*, short, short, short);
 int unlink(char*);
 void iupdate(struct inode*);
 int link(char*, char*);
+struct inode* igetroot(void);
 
 // number of elements in fixed-size array
 #define NELEM(x) (sizeof(x)/sizeof((x)[0]))

fs.h

@@ -55,5 +55,3 @@ struct dirent {
   char name[DIRSIZ];
 };
 
-extern uint rootdev;  // Device number of root file system
-

fsvar.h

@@ -14,7 +14,7 @@ struct inode {
   uint addrs[NADDRS];
 };
 
-extern uint rootdev;
+#define ROOTDEV  1   // Device number of root file system
 
 #define NAMEI_LOOKUP 1
 #define NAMEI_CREATE 2

main.c

@@ -125,7 +125,7 @@ process0(void)
   release(&proc_table_lock);
 
   p0 = &proc[0];
-  p0->cwd = iget(rootdev, 1);
+  p0->cwd = igetroot();
   iunlock(p0->cwd);
 
   // Dummy user memory to make copyproc() happy.