From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from szxga01-in.huawei.com ([58.251.152.64]:50827 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752664AbdADB52 (ORCPT ); Tue, 3 Jan 2017 20:57:28 -0500 Subject: Re: [PATCH] f2fs: fix small discards when se->valid_blocks is zero To: Yunlong Song , , , , References: <1483434117-24427-1-git-send-email-yunlong.song@huawei.com> CC: , , , From: Chao Yu Message-ID: <72699809-4316-0390-a09b-eb5d5fc70981@huawei.com> Date: Wed, 4 Jan 2017 09:54:29 +0800 MIME-Version: 1.0 In-Reply-To: <1483434117-24427-1-git-send-email-yunlong.song@huawei.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On 2017/1/3 17:01, Yunlong Song wrote: > In the small discard case, when se->valid_blocks is zero, the add_discard_addrs > will directly return without __add_discard_entry. This will cause the file > delete have no small discard. The case is like this: > > 1. Allocate free 2M segment > 2. Write a file (size n blocks < 512) in that 2M segment, se->valid_blocks = n > 3. Delete that file, se->valid_blocks = 0, add_discard_addrs will return without > sending any discard of that file, and forever due to cur_map[i] ^ ckpt_map[i] = > 0 after that checkpoint Wouldn't it be discarded as prefree segment? Thanks, > > Signed-off-by: Yunlong Song > --- > fs/f2fs/segment.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c > index 0738f48..8610f14 100644 > --- a/fs/f2fs/segment.c > +++ b/fs/f2fs/segment.c > @@ -838,7 +838,7 @@ static void add_discard_addrs(struct f2fs_sb_info *sbi, struct cp_control *cpc) > return; > > if (!force) { > - if (!test_opt(sbi, DISCARD) || !se->valid_blocks || > + if (!test_opt(sbi, DISCARD) || > SM_I(sbi)->nr_discards >= SM_I(sbi)->max_discards) > return; > } >