[PATCH v5 07/13] fs: remove inode::i_crypt_info

[Eric Biggers <ebiggers@xxxxxxxxxx>]

Now that all fscrypt-capable filesystems store the pointer to
fscrypt_inode_info in the filesystem-specific part of the inode
structure, inode::i_crypt_info is no longer needed.  Update
fscrypt_inode_info_addr() to no longer support the fallback to
inode::i_crypt_info.  Finally, remove inode::i_crypt_info itself along
with the now-unnecessary forward declaration of fscrypt_inode_info.

The end result of the migration to the filesystem-specific pointer is
memory savings on CONFIG_FS_ENCRYPTION=y kernels for all filesystems
that don't support fscrypt.  Specifically, their in-memory inodes are
now smaller by the size of a pointer: either 4 or 8 bytes.

Co-developed-by: Christian Brauner <brauner@xxxxxxxxxx>
Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
---
 include/linux/fs.h      | 5 -----
 include/linux/fscrypt.h | 8 ++++++--
 2 files changed, 6 insertions(+), 7 deletions(-)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index d7ab4f96d7051..1dafa18169be6 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -70,11 +70,10 @@ struct vfsmount;
 struct cred;
 struct swap_info_struct;
 struct seq_file;
 struct workqueue_struct;
 struct iov_iter;
-struct fscrypt_inode_info;
 struct fscrypt_operations;
 struct fsverity_info;
 struct fsverity_operations;
 struct fsnotify_mark_connector;
 struct fsnotify_sb_info;
@@ -778,14 +777,10 @@ struct inode {
 	__u32			i_fsnotify_mask; /* all events this inode cares about */
 	/* 32-bit hole reserved for expanding i_fsnotify_mask */
 	struct fsnotify_mark_connector __rcu	*i_fsnotify_marks;
 #endif
 
-#ifdef CONFIG_FS_ENCRYPTION
-	struct fscrypt_inode_info	*i_crypt_info;
-#endif
-
 #ifdef CONFIG_FS_VERITY
 	struct fsverity_info	*i_verity_info;
 #endif
 
 	void			*i_private; /* fs or device private pointer */
diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h
index d7ff53accbfef..516aba5b858b5 100644
--- a/include/linux/fscrypt.h
+++ b/include/linux/fscrypt.h
@@ -199,15 +199,19 @@ struct fscrypt_operations {
 };
 
 int fscrypt_d_revalidate(struct inode *dir, const struct qstr *name,
 			 struct dentry *dentry, unsigned int flags);
 
+/*
+ * Returns the address of the fscrypt info pointer within the
+ * filesystem-specific part of the inode.  (To save memory on filesystems that
+ * don't support fscrypt, a field in 'struct inode' itself is no longer used.)
+ */
 static inline struct fscrypt_inode_info **
 fscrypt_inode_info_addr(const struct inode *inode)
 {
-	if (inode->i_sb->s_cop->inode_info_offs == 0)
-		return (struct fscrypt_inode_info **)&inode->i_crypt_info;
+	VFS_WARN_ON_ONCE(inode->i_sb->s_cop->inode_info_offs == 0);
 	return (void *)inode + inode->i_sb->s_cop->inode_info_offs;
 }
 
 /*
  * Load the inode's fscrypt info pointer, using a raw dereference.  Since this
-- 
2.50.1