From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7146F18A6B5 for ; Mon, 17 Mar 2025 07:12:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742195576; cv=none; b=jbPY9MyIP/JzBEhxwb3pXEMvLfsgiAW4UV562YDh+NuId8BatlCrHI0YEhD4tnlOLKnA00cagIIgun+11a4oPSFWo4/fsX/1o7s+lI0Mp8ciaDST7g9MznWDz9ppYjb1dbb+wKbvt9H1YXJXTQEYIIYb3u3EsPQ+z6l/ORy0VpQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742195576; c=relaxed/simple; bh=8CS4msPxk4DCirERvuRrksmNRWtm494ZCr116H0cv0I=; h=Message-ID:Date:MIME-Version:Cc:Subject:To:References:From: In-Reply-To:Content-Type; b=nI7AmLbWTQlB5R5lpBy1N+4qMg8X5L8prnyDdI4SQk8PKdFU7hQUbsxzZF7X0cjHxAbR+3ALhNkhrryMNkRHt8zqSA9hBRaO2LXi0B/3xeY7pX8H+bzEJgYhfvf0JkKssmc1GfKtyjPQpDaqc1tl9i6u/7Idh2/N3ZQUCv869Hk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=LF62dsWd; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="LF62dsWd" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5B2DFC4CEE3; Mon, 17 Mar 2025 07:12:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1742195576; bh=8CS4msPxk4DCirERvuRrksmNRWtm494ZCr116H0cv0I=; h=Date:Cc:Subject:To:References:From:In-Reply-To:From; b=LF62dsWd9hmoMcCslTEilzyXJHFy/cmN8CxKod0XPZRyzzmfvTheXhT9/p+iFgH4B v4UFJHUrh0HrqZfW8i0M3gL6Zlb9Ltw1VREPojlOiXryU0D4sFQI0AiXpPSosWHgnx /Wq/AcGHdbB8M4JCsS2oDgPjDeFcHNukHBvFsggRIwoBdkQle6RWeNFN10doNU2A4+ SeRZLScE4awskkiblmxaoTBzbe7zQsroyGJvPIbmfU9hzwMuTE3ubrc5CxEDJyxTM3 BoxOCb9kIqH/UGs4Xes0EU/pYSauaVSI+yHvJObNIU6kfdnbu15muYAobrHOOdbEZ3 skboG043PBhOw== Message-ID: <6ad02c17-a175-43fd-bce4-d3cd2dc01338@kernel.org> Date: Mon, 17 Mar 2025 15:12:53 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Cc: chao@kernel.org, "linux-f2fs-devel@lists.sourceforge.net" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH v2] f2fs: fix missing discard for active segments To: Chunhai Guo , "jaegeuk@kernel.org" References: <20250109122755.177926-1-guochunhai@vivo.com> <4270b213-e4f9-46b2-958a-df3dbaaed969@kernel.org> <95b8334a-45e6-496a-8b0b-ab7a7fe180b5@vivo.com> Content-Language: en-US From: Chao Yu In-Reply-To: <95b8334a-45e6-496a-8b0b-ab7a7fe180b5@vivo.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 3/13/25 10:25, Chunhai Guo wrote: > 在 1/20/2025 8:25 PM, Chao Yu 写道: >> On 1/9/25 20:27, Chunhai Guo wrote: >>> During a checkpoint, the current active segment X may not be handled >>> properly. This occurs when segment X has 0 valid blocks and a non-zero >> How does this happen? Allocator selects a dirty segment w/ SSR? and the >> left valid data blocks were deleted later before following checkpoint? >> >> If so, pending discard count in that segment should be in range of (0, 512)? > > > This issue is found with LFS rather than SSR. Here's what happens: some > data blocks are allocated for a file in the current active segment, and > then the file is deleted, resulting in all valid data blocks in the > current active segment being deleted before the following checkpoint. > This issue is easy to reproduce with the following operations: > > > # mkfs.f2fs -f /dev/nvme2n1 > # mount -t f2fs /dev/nvme2n1 /vtmp/mnt/f2fs > # dd if=/dev/nvme0n1 of=/vtmp/mnt/f2fs/1.bin bs=4k count=256 > # sync > # rm /vtmp/mnt/f2fs/1.bin > # umount /vtmp/mnt/f2fs > # dump.f2fs /dev/nvme2n1 | grep "checkpoint state" > Info: checkpoint state = 45 : crc compacted_summary unmount ---- > 'trimmed' flag is missing > > The pending discard count in that segment indeed falls within the range > of (0, 512). Please add this testcase into commit message, otherwise it looks good to me, feel free to add: Reviewed-by: Chao Yu Thanks, > > Thanks, >> Thanks, >> >>> number of discard blocks, for the following reasons: >>> >>> locate_dirty_segment() does not mark any active segment as a prefree >>> segment. As a result, segment X is not included in dirty_segmap[PRE], and >>> f2fs_clear_prefree_segments() skips it when handling prefree segments. >>> >>> add_discard_addrs() skips any segment with 0 valid blocks, so segment X is >>> also skipped. >>> >>> Consequently, no `struct discard_cmd` is actually created for segment X. >>> However, the ckpt_valid_map and cur_valid_map of segment X are synced by >>> seg_info_to_raw_sit() during the current checkpoint process. As a result, >>> it cannot find the missing discard bits even in subsequent checkpoints. >>> Consequently, the value of sbi->discard_blks remains non-zero. Thus, when >>> f2fs is umounted, CP_TRIMMED_FLAG will not be set due to the non-zero >>> sbi->discard_blks. >>> >>> Relevant code process: >>> >>> f2fs_write_checkpoint() >>> f2fs_flush_sit_entries() >>> list_for_each_entry_safe(ses, tmp, head, set_list) { >>> for_each_set_bit_from(segno, bitmap, end) { >>> ... >>> add_discard_addrs(sbi, cpc, false); // skip segment X due to its 0 valid blocks >>> ... >>> seg_info_to_raw_sit(); // sync ckpt_valid_map with cur_valid_map for segment X >>> ... >>> } >>> } >>> f2fs_clear_prefree_segments(); // segment X is not included in dirty_segmap[PRE] and is skipped >>> >>> Since add_discard_addrs() can handle active segments with non-zero valid >>> blocks, it is reasonable to fix this issue by allowing it to also handle >>> active segments with 0 valid blocks. >>> >>> Fixes: b29555505d81 ("f2fs: add key functions for small discards") >>> Signed-off-by: Chunhai Guo >>> --- >>> v1: https://lore.kernel.org/linux-f2fs-devel/20241203065108.2763436-1-guochunhai@vivo.com/ >>> v1->v2: >>> - Modify the commit message to make it easier to understand. >>> - Add fixes to the commit. >>> --- >>> fs/f2fs/segment.c | 4 +++- >>> 1 file changed, 3 insertions(+), 1 deletion(-) >>> >>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c >>> index 86e547f008f9..13ee73a3c481 100644 >>> --- a/fs/f2fs/segment.c >>> +++ b/fs/f2fs/segment.c >>> @@ -2090,7 +2090,9 @@ static bool add_discard_addrs(struct f2fs_sb_info *sbi, struct cp_control *cpc, >>> return false; >>> >>> if (!force) { >>> - if (!f2fs_realtime_discard_enable(sbi) || !se->valid_blocks || >>> + if (!f2fs_realtime_discard_enable(sbi) || >>> + (!se->valid_blocks && >>> + !IS_CURSEG(sbi, cpc->trim_start)) || >>> SM_I(sbi)->dcc_info->nr_discards >= >>> SM_I(sbi)->dcc_info->max_discards) >>> return false; > >