ext4: move verity info pointer to fs-specific part of inode

Move the fsverity_info pointer into the filesystem-specific part of the
inode by adding the field ext4_inode_info::i_verity_info and configuring
fsverity_operations::inode_info_offs accordingly.

This is a prerequisite for a later commit that removes
inode::i_verity_info, saving memory and improving cache efficiency on
filesystems that don't support fsverity.

Co-developed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Link: https://lore.kernel.org/20250810075706.172910-10-ebiggers@kernel.org
Acked-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Christian Brauner <brauner@kernel.org>

fs/ext4/ext4.h

@@ -1186,6 +1186,10 @@ struct ext4_inode_info {
 #ifdef CONFIG_FS_ENCRYPTION
 	struct fscrypt_inode_info *i_crypt_info;
 #endif
+
+#ifdef CONFIG_FS_VERITY
+	struct fsverity_info *i_verity_info;
+#endif
 };
 
 /*

fs/ext4/super.c

@@ -1473,6 +1473,9 @@ static void init_once(void *foo)
 #ifdef CONFIG_FS_ENCRYPTION
 	ei->i_crypt_info = NULL;
 #endif
+#ifdef CONFIG_FS_VERITY
+	ei->i_verity_info = NULL;
+#endif
 }
 
 static int __init init_inodecache(void)

fs/ext4/verity.c

@@ -389,6 +389,8 @@ static int ext4_write_merkle_tree_block(struct inode *inode, const void *buf,
 }
 
 const struct fsverity_operations ext4_verityops = {
+	.inode_info_offs	= (int)offsetof(struct ext4_inode_info, i_verity_info) -
+				  (int)offsetof(struct ext4_inode_info, vfs_inode),
 	.begin_enable_verity	= ext4_begin_enable_verity,
 	.end_enable_verity	= ext4_end_enable_verity,
 	.get_verity_descriptor	= ext4_get_verity_descriptor,