VFS: swap do_ioctl and vfs_ioctl names

Rename old vfs_ioctl to do_ioctl, because the comment above it clearly
indicates that it is an internal function not to be exported to modules;
therefore it should have a more traditional do_XXX name.  The new do_ioctl
is exported in fs.h but not to modules.

Rename the old do_ioctl to vfs_ioctl because the names vfs_XXX should
preferably be reserved to callable VFS functions which modules may call, as
many other vfs_XXX functions already do.  Export the new vfs_ioctl to GPL
modules so others can use it (including Unionfs and eCryptfs).  Add DocBook
for new vfs_ioctl.

[akpm@linux-foundation.org: fix build]
Signed-off-by: Erez Zadok <ezk@cs.sunysb.edu>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 109734b..2925f70 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1941,7 +1941,9 @@
 extern int vfs_lstat_fd(int dfd, char __user *, struct kstat *);
 extern int vfs_fstat(unsigned int, struct kstat *);
 
-extern int vfs_ioctl(struct file *, unsigned int, unsigned int, unsigned long);
+extern long vfs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg);
+extern int do_vfs_ioctl(struct file *filp, unsigned int fd, unsigned int cmd,
+		    unsigned long arg);
 
 extern void get_filesystem(struct file_system_type *fs);
 extern void put_filesystem(struct file_system_type *fs);