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>
diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h
index c422367..2327859 100644
--- a/include/linux/fscrypt.h
+++ b/include/linux/fscrypt.h
@@ -237,4 +237,32 @@ static inline int fscrypt_prepare_rename(struct inode *old_dir,
return 0;
}
+/**
+ * fscrypt_prepare_lookup - prepare to lookup a name in a possibly-encrypted directory
+ * @dir: directory being searched
+ * @dentry: filename being looked up
+ * @flags: lookup flags
+ *
+ * Prepare for ->lookup() in a directory which may be encrypted. Lookups can be
+ * done with or without the directory's encryption key; without the key,
+ * filenames are presented in encrypted form. Therefore, we'll try to set up
+ * the directory's encryption key, but even without it the lookup can continue.
+ *
+ * To allow invalidating stale dentries if the directory's encryption key is
+ * added later, we also install a custom ->d_revalidate() method and use the
+ * DCACHE_ENCRYPTED_WITH_KEY flag to indicate whether a given dentry is a
+ * plaintext name (flag set) or a ciphertext name (flag cleared).
+ *
+ * Return: 0 on success, -errno if a problem occurred while setting up the
+ * encryption key
+ */
+static inline int fscrypt_prepare_lookup(struct inode *dir,
+ struct dentry *dentry,
+ unsigned int flags)
+{
+ if (IS_ENCRYPTED(dir))
+ return __fscrypt_prepare_lookup(dir, dentry);
+ return 0;
+}
+
#endif /* _LINUX_FSCRYPT_H */