From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx2.suse.de ([195.135.220.15]:47640 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751680AbdHAP0B (ORCPT ); Tue, 1 Aug 2017 11:26:01 -0400 Received: from relay2.suse.de (charybdis-ext.suse.de [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 1F95BABDD for ; Tue, 1 Aug 2017 15:26:00 +0000 (UTC) From: Nikolay Borisov To: linux-btrfs@vger.kernel.org Cc: Nikolay Borisov Subject: [PATCH] btrfs: remove broken memory barrier Date: Tue, 1 Aug 2017 18:25:56 +0300 Message-Id: <1501601156-19585-1-git-send-email-nborisov@suse.com> Sender: linux-btrfs-owner@vger.kernel.org List-ID: Commit 38851cc19adb ("Btrfs: implement unlocked dio write") implemented unlocked dio write, allowing multiple dio writers to write to non-overlapping, and non-eof-extending regions. In doing so it also introduced a broken memory barrier. It is broken due to 2 things: 1. Memory barriers _MUST_ always be paired, this is clearly not the case here 2. Checkpatch actually produces a warning if a memory barrier is introduced that doesn't have a comment explaining how it's being paired. Signed-off-by: Nikolay Borisov --- fs/btrfs/inode.c | 1 - 1 file changed, 1 deletion(-) diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index 95c212037095..5e48d2c10152 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -8731,7 +8731,6 @@ static ssize_t btrfs_direct_IO(struct kiocb *iocb, struct iov_iter *iter) return 0; inode_dio_begin(inode); - smp_mb__after_atomic(); /* * The generic stuff only does filemap_write_and_wait_range, which -- 2.7.4