hfsplus: remove hfsplus_file_lookup()

HFS+ resource fork lookup breaks opendir() library function.  Since
opendir first calls open() with O_DIRECTORY flag set.  O_DIRECTORY means
"refuse to open if not a directory".  The open system call in the kernel
does a check for inode->i_op->lookup and returns -ENOTDIR.  So if
hfsplus_file_lookup is set it allows opendir() for plain files.

Also resource fork lookup in HFS+ does not work.  Since it is never
invoked after VFS permission checking.  It will always return with
-EACCES.

When we call opendir() on a file, it does not return NULL.  opendir()
library call is based on open with O_DIRECTORY flag passed and then
layered on top of getdents() system call.  O_DIRECTORY means "refuse to
open if not a directory".

The open() system call in the kernel does a check for: do_sys_open()
-->..--> can_lookup() i.e it only checks inode->i_op->lookup and returns
ENOTDIR if this function pointer is not set.

In OSX, we can open "file/rsrc" to get the resource fork of "file".  This
behavior is emulated inside hfsplus on Linux, which means that to some
degree every file acts like a directory.  That is the reason lookup()
inode operations is supported for files, and it is possible to do a lookup
on this specific name.  As a result of this open succeeds without
returning ENOTDIR for HFS+

Please see the LKML discussion thread on this issue:
http://marc.info/?l=linux-fsdevel&m=122823343730412&w=2

I tried to test file/rsrc lookup in HFS+ driver and the feature does not
work.  From OSX:

$ touch test
$ echo "1234" > test/..namedfork/rsrc
$ ls -l test..namedfork/rsrc
--rw-r--r-- 1 tuxera staff 5 10 dec 12:59 test/..namedfork/rsrc

[sougata@ultrabook tmp]$ id
uid=1000(sougata) gid=1000(sougata) groups=1000(sougata),5(tty),18(dialout),1001(vboxusers)

[sougata@ultrabook tmp]$ mount
/dev/sdb1 on /mnt/tmp type hfsplus (rw,relatime,umask=0,uid=1000,gid=1000,nls=utf8)

[sougata@ultrabook tmp]$ ls -l test/rsrc
ls: cannot access test/rsrc: Permission denied

According to this LKML thread it is expected behavior.

http://marc.info/?t=121139033800008&r=1&w=4

I guess now that permission checking happens in vfs generic_permission() ?
 So it turns out that even though the lookup() inode_operation exists for
HFS+ files.  It cannot really get invoked ?.  So if we can disable this
feature to make opendir() work for HFS+.

Signed-off-by: Sougata Santra <sougata@tuxera.com>
Acked-by: Christoph Hellwig <hch@lst.de>
Cc: Vyacheslav Dubeyko <slava@dubeyko.com>
Cc: Anton Altaparmakov <aia21@cam.ac.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/hfsplus/inode.c

@@ -178,64 +178,6 @@ const struct dentry_operations hfsplus_dentry_operations = {
 	.d_compare    = hfsplus_compare_dentry,
 };
 
-static struct dentry *hfsplus_file_lookup(struct inode *dir,
-		struct dentry *dentry, unsigned int flags)
-{
-	struct hfs_find_data fd;
-	struct super_block *sb = dir->i_sb;
-	struct inode *inode = NULL;
-	struct hfsplus_inode_info *hip;
-	int err;
-
-	if (HFSPLUS_IS_RSRC(dir) || strcmp(dentry->d_name.name, "rsrc"))
-		goto out;
-
-	inode = HFSPLUS_I(dir)->rsrc_inode;
-	if (inode)
-		goto out;
-
-	inode = new_inode(sb);
-	if (!inode)
-		return ERR_PTR(-ENOMEM);
-
-	hip = HFSPLUS_I(inode);
-	inode->i_ino = dir->i_ino;
-	INIT_LIST_HEAD(&hip->open_dir_list);
-	mutex_init(&hip->extents_lock);
-	hip->extent_state = 0;
-	hip->flags = 0;
-	hip->userflags = 0;
-	set_bit(HFSPLUS_I_RSRC, &hip->flags);
-
-	err = hfs_find_init(HFSPLUS_SB(sb)->cat_tree, &fd);
-	if (!err) {
-		err = hfsplus_find_cat(sb, dir->i_ino, &fd);
-		if (!err)
-			err = hfsplus_cat_read_inode(inode, &fd);
-		hfs_find_exit(&fd);
-	}
-	if (err) {
-		iput(inode);
-		return ERR_PTR(err);
-	}
-	hip->rsrc_inode = dir;
-	HFSPLUS_I(dir)->rsrc_inode = inode;
-	igrab(dir);
-
-	/*
-	 * __mark_inode_dirty expects inodes to be hashed.  Since we don't
-	 * want resource fork inodes in the regular inode space, we make them
-	 * appear hashed, but do not put on any lists.  hlist_del()
-	 * will work fine and require no locking.
-	 */
-	hlist_add_fake(&inode->i_hash);
-
-	mark_inode_dirty(inode);
-out:
-	d_add(dentry, inode);
-	return NULL;
-}
-
 static void hfsplus_get_perms(struct inode *inode,
 		struct hfsplus_perm *perms, int dir)
 {
@@ -385,7 +327,6 @@ int hfsplus_file_fsync(struct file *file, loff_t start, loff_t end,
 }
 
 static const struct inode_operations hfsplus_file_inode_operations = {
-	.lookup		= hfsplus_file_lookup,
 	.setattr	= hfsplus_setattr,
 	.setxattr	= generic_setxattr,
 	.getxattr	= generic_getxattr,