ext4: only check dquot_initialize_needed() when debugging

ext4_xattr_block_set() relies on its caller to call dquot_initialize()
on the inode. To assure that this has happened there are WARN_ON
checks. Unfortunately, this is subject to false positives if there is
an antagonist thread which is flipping the file system at high rates
between r/o and rw. So only do the check if EXT4_XATTR_DEBUG is
enabled.

Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Theodore Ts'o <[e-mail]>

fs/ext4/xattr.c

···
 			else {
 				u32 ref;
 
+#ifdef EXT4_XATTR_DEBUG
 				WARN_ON_ONCE(dquot_initialize_needed(inode));
-
+#endif
 				/* The old block is released after updating
 				   the inode. */
 				error = dquot_alloc_block(inode,
···
 			/* We need to allocate a new block */
 			ext4_fsblk_t goal, block;
 
+#ifdef EXT4_XATTR_DEBUG
 			WARN_ON_ONCE(dquot_initialize_needed(inode));
-
+#endif
 			goal = ext4_group_first_block_no(sb,
 						EXT4_I(inode)->i_block_group);
 			block = ext4_new_meta_blocks(handle, inode, goal, 0,