fscrypt: new helper function - fscrypt_prepare_lookup()

Introduce a helper function which prepares to look up the given dentry
in the given directory.  If the directory is encrypted, it handles
loading the directory's encryption key, setting the dentry's ->d_op to
fscrypt_d_ops, and setting DCACHE_ENCRYPTED_WITH_KEY if the directory's
encryption key is available.

Note: once all filesystems switch over to this, we'll be able to move
fscrypt_d_ops and fscrypt_set_encrypted_dentry() to fscrypt_private.h.

Acked-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

1 files changed, 18 insertions, 0 deletions

diff --git a/fs/crypto/hooks.c b/fs/crypto/hooks.c
index 822cb78f9b45..9f5fb2eb9cf7 100644
--- a/fs/crypto/hooks.c
+++ b/fs/crypto/hooks.c
@@ -92,3 +92,21 @@ int __fscrypt_prepare_rename(struct inode *old_dir, struct dentry *old_dentry,
 	return 0;
 }
 EXPORT_SYMBOL_GPL(__fscrypt_prepare_rename);
+
+int __fscrypt_prepare_lookup(struct inode *dir, struct dentry *dentry)
+{
+	int err = fscrypt_get_encryption_info(dir);
+
+	if (err)
+		return err;
+
+	if (fscrypt_has_encryption_key(dir)) {
+		spin_lock(&dentry->d_lock);
+		dentry->d_flags |= DCACHE_ENCRYPTED_WITH_KEY;
+		spin_unlock(&dentry->d_lock);
+	}
+
+	d_set_d_op(dentry, &fscrypt_d_ops);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(__fscrypt_prepare_lookup);