[PATCH 3/5] libfs: Add generic function for setting dentry_ops

[Daniel Rosenberg <drosen@google.com>]

This adds a function to set dentry operations at lookup time that will
work for both encrypted files and casefolded filenames.

A filesystem that supports both features simultaneously can use this
function during lookup preperations to set up its dentry operations once
fscrypt no longer does that itself.

Currently the casefolding dentry operation are always set because the
feature is toggleable on empty directories. Since we don't know what
set of functions we'll eventually need, and cannot change them later,
we add just add them.

Signed-off-by: Daniel Rosenberg <drosen@google.com>
---
 fs/libfs.c         | 49 ++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/fs.h |  1 +
 2 files changed, 50 insertions(+)

diff --git a/fs/libfs.c b/fs/libfs.c
index fc34361c1489..83303858f1fe 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -1449,4 +1449,53 @@ int generic_ci_d_hash(const struct dentry *dentry, struct qstr *str)
 	return 0;
 }
 EXPORT_SYMBOL(generic_ci_d_hash);
+
+static const struct dentry_operations generic_ci_dentry_ops = {
+	.d_hash = generic_ci_d_hash,
+	.d_compare = generic_ci_d_compare,
+};
+#endif
+
+#ifdef CONFIG_FS_ENCRYPTION
+static const struct dentry_operations generic_encrypted_dentry_ops = {
+	.d_revalidate = fscrypt_d_revalidate,
+};
+#endif
+
+#if IS_ENABLED(CONFIG_UNICODE) && IS_ENABLED(CONFIG_FS_ENCRYPTION)
+static const struct dentry_operations generic_encrypted_ci_dentry_ops = {
+	.d_hash = generic_ci_d_hash,
+	.d_compare = generic_ci_d_compare,
+	.d_revalidate = fscrypt_d_revalidate,
+};
+#endif
+
+/**
+ * generic_set_encrypted_ci_d_ops - helper for setting d_ops for given dentry
+ * @dentry:	dentry to set ops on
+ *
+ * This function sets the dentry ops for the given dentry to handle both
+ * casefolding and encryption of the dentry name.
+ */
+void generic_set_encrypted_ci_d_ops(struct dentry *dentry)
+{
+#ifdef CONFIG_FS_ENCRYPTION
+	if (dentry->d_flags & DCACHE_ENCRYPTED_NAME) {
+#ifdef CONFIG_UNICODE
+		if (dentry->d_sb->s_encoding) {
+			d_set_d_op(dentry, &generic_encrypted_ci_dentry_ops);
+			return;
+		}
 #endif
+		d_set_d_op(dentry, &generic_encrypted_dentry_ops);
+		return;
+	}
+#endif
+#ifdef CONFIG_UNICODE
+	if (dentry->d_sb->s_encoding) {
+		d_set_d_op(dentry, &generic_ci_dentry_ops);
+		return;
+	}
+#endif
+}
+EXPORT_SYMBOL(generic_set_encrypted_ci_d_ops);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index bc5417c61e12..6627896db835 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3277,6 +3277,7 @@ extern int generic_ci_d_hash(const struct dentry *dentry, struct qstr *str);
 extern int generic_ci_d_compare(const struct dentry *dentry, unsigned int len,
 				const char *str, const struct qstr *name);
 #endif
+extern void generic_set_encrypted_ci_d_ops(struct dentry *dentry);
 
 #ifdef CONFIG_MIGRATION
 extern int buffer_migrate_page(struct address_space *,
-- 
2.28.0.681.g6f77f65b4e-goog