ext4: set lockdep subclass for the ea_inode in ext4_xattr_inode_cache_find()

If the ea_inode has been pushed out of the inode cache while there is
still a reference in the mb_cache, the lockdep subclass will not be
set on the inode, which can lead to some lockdep false positives.

Fixes: 33d201e0 ("ext4: fix lockdep warning about recursive inode locking")
Cc: stable@kernel.org
Reported-by: syzbot+d4b971e744b1f5439336@syzkaller.appspotmail.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Link: https://lore.kernel.org/r/20230524034951.779531-3-tytso@mit.eduSigned-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/xattr.c

@@ -1539,6 +1539,7 @@ ext4_xattr_inode_cache_find(struct inode *inode, const void *value,
 				     EXT4_IGET_EA_INODE);
 		if (IS_ERR(ea_inode))
 			goto next_entry;
+		ext4_xattr_inode_set_class(ea_inode);
 		if (i_size_read(ea_inode) == value_len &&
 		    !ext4_xattr_inode_read(ea_inode, ea_data, value_len) &&
 		    !ext4_xattr_inode_verify_hashes(ea_inode, NULL, ea_data,