comment nits

kernel/exec.c

@@ -65,6 +65,7 @@ exec(char *path, char **argv)
   uint64 oldsz = p->sz;
 
   // Allocate two pages at the next page boundary.
+  // Make the first inaccessible as a stack guard.
   // Use the second as the user stack.
   sz = PGROUNDUP(sz);
   uint64 sz1;

kernel/fs.c

@@ -109,8 +109,8 @@ bfree(int dev, uint b)
 // its size, the number of links referring to it, and the
 // list of blocks holding the file's content.
 //
-// The inodes are laid out sequentially on disk at block
-// sb.inodestart. Each inode has a number, indicating its
+// The inodes are laid out sequentially on disk at
+// sb.startinode. Each inode has a number, indicating its
 // position on the disk.
 //
 // The kernel keeps a table of in-use inodes in memory