btrfs: setup qstr from dentrys using fscrypt helper

[ Upstream commit ab3c5c1 ]

Most places where we get a struct qstr, we are doing so from a dentry.
With fscrypt, the dentry's name may be encrypted on-disk, so fscrypt
provides a helper to convert a dentry name to the appropriate disk name
if necessary. Convert each of the dentry name accesses to use
fscrypt_setup_filename(), then convert the resulting fscrypt_name back
to an unencrypted qstr. This does not work for nokey names, but the
specific locations that could spawn nokey names are noted.

At present, since there are no encrypted directories, nothing goes down
the filename encryption paths.

Signed-off-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Stable-dep-of: 9af8669 ("btrfs: file_remove_privs needs an exclusive lock in direct io write")
Signed-off-by: Sasha Levin <sashal@kernel.org>

fs/btrfs/ctree.h

@@ -28,6 +28,7 @@
 #include <linux/refcount.h>
 #include <linux/crc32c.h>
 #include <linux/iomap.h>
+#include <linux/fscrypt.h>
 #include "extent-io-tree.h"
 #include "extent_io.h"
 #include "extent_map.h"
@@ -3396,6 +3397,8 @@ struct btrfs_new_inode_args {
 	 */
 	struct posix_acl *default_acl;
 	struct posix_acl *acl;
+	struct fscrypt_name fname;
+	struct qstr name;
 };
 int btrfs_new_inode_prepare(struct btrfs_new_inode_args *args,
 			    unsigned int *trans_num_items);