FROMLIST: fscrypt: Have filesystems handle their d_ops

This shifts the responsibility of setting up dentry operations from
fscrypt to the individual filesystems, allowing them to have their own
operations while still setting fscrypt's d_revalidate as appropriate.

Also added helper function to libfs to unify ext4 and f2fs
implementations.

Signed-off-by: Daniel Rosenberg <drosen@google.com>
Test: Boots, /data/media is case insensitive
Bug: 138322712
Link: https://lore.kernel.org/linux-f2fs-devel/20200208013552.241832-1-drosen@google.com/T/#t
Change-Id: Iaf77f8c5961ecf22e22478701ab0b7fe2025225d

fs/crypto/fname.c

@@ -543,7 +543,7 @@ EXPORT_SYMBOL_GPL(fscrypt_fname_siphash);
  * Validate dentries in encrypted directories to make sure we aren't potentially
  * caching stale dentries after a key has been added.
  */
-static int fscrypt_d_revalidate(struct dentry *dentry, unsigned int flags)
+int fscrypt_d_revalidate(struct dentry *dentry, unsigned int flags)
 {
 	struct dentry *dir;
 	int err;
@@ -582,7 +582,4 @@ static int fscrypt_d_revalidate(struct dentry *dentry, unsigned int flags)
 
 	return valid;
 }
-
-const struct dentry_operations fscrypt_d_ops = {
-	.d_revalidate = fscrypt_d_revalidate,
-};
+EXPORT_SYMBOL(fscrypt_d_revalidate);

fs/crypto/fscrypt_private.h

@@ -275,7 +275,6 @@ extern int fscrypt_fname_encrypt(const struct inode *inode,
 extern bool fscrypt_fname_encrypted_size(const struct inode *inode,
 					 u32 orig_len, u32 max_len,
 					 u32 *encrypted_len_ret);
-extern const struct dentry_operations fscrypt_d_ops;
 
 /* hkdf.c */
 

fs/crypto/hooks.c

@@ -118,7 +118,6 @@ int __fscrypt_prepare_lookup(struct inode *dir, struct dentry *dentry,
 		spin_lock(&dentry->d_lock);
 		dentry->d_flags |= DCACHE_ENCRYPTED_NAME;
 		spin_unlock(&dentry->d_lock);
-		d_set_d_op(dentry, &fscrypt_d_ops);
 	}
 	return err;
 }

fs/ext4/dir.c

@@ -667,10 +667,3 @@ const struct file_operations ext4_dir_operations = {
 	.open		= ext4_dir_open,
 	.release	= ext4_release_dir,
 };
-
-#ifdef CONFIG_UNICODE
-const struct dentry_operations ext4_dentry_ops = {
-	.d_hash = generic_ci_d_hash,
-	.d_compare = generic_ci_d_compare,
-};
-#endif

fs/ext4/namei.c

@@ -1614,6 +1614,7 @@ static struct buffer_head *ext4_lookup_entry(struct inode *dir,
 	struct buffer_head *bh;
 
 	err = ext4_fname_prepare_lookup(dir, dentry, &fname);
+	generic_set_encrypted_ci_d_ops(dir, dentry);
 	if (err == -ENOENT)
 		return NULL;
 	if (err)

fs/ext4/super.c

@@ -4551,11 +4551,6 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 		goto failed_mount4;
 	}
 
-#ifdef CONFIG_UNICODE
-	if (sb->s_encoding)
-		sb->s_d_op = &ext4_dentry_ops;
-#endif
-
 	sb->s_root = d_make_root(root);
 	if (!sb->s_root) {
 		ext4_msg(sb, KERN_ERR, "get root dentry failed");

fs/f2fs/dir.c

@@ -1077,10 +1077,3 @@ const struct file_operations f2fs_dir_operations = {
 	.compat_ioctl   = f2fs_compat_ioctl,
 #endif
 };
-
-#ifdef CONFIG_UNICODE
-const struct dentry_operations f2fs_dentry_ops = {
-	.d_hash = generic_ci_d_hash,
-	.d_compare = generic_ci_d_compare,
-};
-#endif

fs/f2fs/f2fs.h

@@ -3629,9 +3629,6 @@ static inline void update_sit_info(struct f2fs_sb_info *sbi) {}
 #endif
 
 extern const struct file_operations f2fs_dir_operations;
-#ifdef CONFIG_UNICODE
-extern const struct dentry_operations f2fs_dentry_ops;
-#endif
 extern const struct file_operations f2fs_file_operations;
 extern const struct inode_operations f2fs_file_inode_operations;
 extern const struct address_space_operations f2fs_dblock_aops;

fs/f2fs/namei.c

@@ -494,6 +494,7 @@ static struct dentry *f2fs_lookup(struct inode *dir, struct dentry *dentry,
 	}
 
 	err = fscrypt_prepare_lookup(dir, dentry, &fname);
+	generic_set_encrypted_ci_d_ops(dir, dentry);
 	if (err == -ENOENT)
 		goto out_splice;
 	if (err)

fs/f2fs/super.c

@@ -3297,7 +3297,6 @@ static int f2fs_setup_casefold(struct f2fs_sb_info *sbi)
 
 		sbi->sb->s_encoding = encoding;
 		sbi->sb->s_encoding_flags = encoding_flags;
-		sbi->sb->s_d_op = &f2fs_dentry_ops;
 	}
 #else
 	if (f2fs_sb_has_casefold(sbi)) {

fs/libfs.c

@@ -1421,4 +1421,54 @@ int generic_ci_d_hash(const struct dentry *dentry, struct qstr *str)
 	return ret;
 }
 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
+ * @dir:	parent of dentry whose ops to set
+ * @dentry:	detnry 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 inode *dir, struct dentry *dentry)
+{
+#ifdef CONFIG_FS_ENCRYPTION
+	if (dentry->d_flags & DCACHE_ENCRYPTED_NAME) {
+#ifdef CONFIG_UNICODE
+		if (dir->i_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 (dir->i_sb->s_encoding) {
+		d_set_d_op(dentry, &generic_ci_dentry_ops);
+		return;
+	}
+#endif
+}
+EXPORT_SYMBOL(generic_set_encrypted_ci_d_ops);

fs/ubifs/dir.c

@@ -196,6 +196,7 @@ static int dbg_check_name(const struct ubifs_info *c,
 	return 0;
 }
 
+static void ubifs_set_d_ops(struct inode *dir, struct dentry *dentry);
 static struct dentry *ubifs_lookup(struct inode *dir, struct dentry *dentry,
 				   unsigned int flags)
 {
@@ -209,6 +210,7 @@ static struct dentry *ubifs_lookup(struct inode *dir, struct dentry *dentry,
 	dbg_gen("'%pd' in dir ino %lu", dentry, dir->i_ino);
 
 	err = fscrypt_prepare_lookup(dir, dentry, &nm);
+	ubifs_set_d_ops(dir, dentry);
 	if (err == -ENOENT)
 		return d_splice_alias(NULL, dentry);
 	if (err)
@@ -1655,3 +1657,19 @@ const struct file_operations ubifs_dir_operations = {
 	.compat_ioctl   = ubifs_compat_ioctl,
 #endif
 };
+
+#ifdef CONFIG_FS_ENCRYPTION
+static const struct dentry_operations ubifs_encrypted_dentry_ops = {
+	.d_revalidate = fscrypt_d_revalidate,
+};
+#endif
+
+static void ubifs_set_d_ops(struct inode *dir, struct dentry *dentry)
+{
+#ifdef CONFIG_FS_ENCRYPTION
+	if (dentry->d_flags & DCACHE_ENCRYPTED_NAME) {
+		d_set_d_op(dentry, &ubifs_encrypted_dentry_ops);
+		return;
+	}
+#endif
+}

include/linux/fs.h

@@ -3411,6 +3411,8 @@ static inline bool needs_casefold(const struct inode *dir)
 	return 0;
 }
 #endif
+extern void generic_set_encrypted_ci_d_ops(struct inode *dir,
+					   struct dentry *dentry);
 
 #ifdef CONFIG_MIGRATION
 extern int buffer_migrate_page(struct address_space *,

include/linux/fscrypt.h

@@ -138,6 +138,7 @@ static inline struct page *fscrypt_pagecache_page(struct page *bounce_page)
 }
 
 extern void fscrypt_free_bounce_page(struct page *bounce_page);
+extern int fscrypt_d_revalidate(struct dentry *dentry, unsigned int flags);
 
 /* policy.c */
 extern int fscrypt_ioctl_set_policy(struct file *, const void __user *);
@@ -681,8 +682,9 @@ static inline int fscrypt_prepare_rename(struct inode *old_dir,
  * 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.
  *
- * This also installs a custom ->d_revalidate() method which will invalidate the
- * dentry if it was created without the key and the key is later added.
+ * After calling this function, a filesystem should ensure that it's dentry
+ * operations contain fscrypt_d_revalidate if DCACHE_ENCRYPTED_NAME was set,
+ * so that the dentry can be invalidated if the key is later added.
  *
  * Return: 0 on success; -ENOENT if key is unavailable but the filename isn't a
  * correctly formed encoded ciphertext name, so a negative dentry should be