ext4: add lockdep annotations for i_data_sem for ea_inode's

Treat i_data_sem for ea_inodes as being in their own lockdep class to
avoid lockdep complaints about ext4_setattr's use of inode_lock() on
normal inodes potentially causing lock ordering with i_data_sem on
ea_inodes in ext4_xattr_inode_write().  However, ea_inodes will be
operated on by ext4_setattr(), so this isn't a problem.

Cc: stable@kernel.org
Link: https://syzkaller.appspot.com/bug?extid=298c5d8fb4a128bc27b0
Reported-by: syzbot+298c5d8fb4a128bc27b0@syzkaller.appspotmail.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Link: https://lore.kernel.org/r/20230524034951.779531-5-tytso@mit.eduSigned-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/ext4.h

@@ -918,11 +918,13 @@ do {									       \
  *			  where the second inode has larger inode number
  *			  than the first
  *  I_DATA_SEM_QUOTA  - Used for quota inodes only
+ *  I_DATA_SEM_EA     - Used for ea_inodes only
  */
 enum {
 	I_DATA_SEM_NORMAL = 0,
 	I_DATA_SEM_OTHER,
 	I_DATA_SEM_QUOTA,
+	I_DATA_SEM_EA
 };
 
 

fs/ext4/xattr.c

@@ -121,7 +121,11 @@ ext4_expand_inode_array(struct ext4_xattr_inode_array **ea_inode_array,
 #ifdef CONFIG_LOCKDEP
 void ext4_xattr_inode_set_class(struct inode *ea_inode)
 {
+	struct ext4_inode_info *ei = EXT4_I(ea_inode);
+
 	lockdep_set_subclass(&ea_inode->i_rwsem, 1);
+	(void) ei;	/* shut up clang warning if !CONFIG_LOCKDEP */
+	lockdep_set_subclass(&ei->i_data_sem, I_DATA_SEM_EA);
 }
 #endif