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 693371B6CEC for ; Mon, 20 Jan 2025 12:25:10 +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=1737375911; cv=none; b=rwtWH2YNPzqcgzpnoeOtBz9Zk2oyyuuqNbfUJJjl59/3mgaAYYbQy3kxxIImjP+SSsJjKINyJz2hA+ig55+f8KNAdtVHd5IImx6jNINMEIoXk/AEU5ew3UdwQ0EgxQNPJehMTOfllvAZFFgRNVaGpnCNdikdXkj5EnT385Zoq6E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737375911; c=relaxed/simple; bh=sPS18muDCtBOUW0OqUdtnsEKIul3j7CdK5hJRv/QnHU=; h=Message-ID:Date:MIME-Version:Cc:Subject:To:References:From: In-Reply-To:Content-Type; b=cNz5STUw1qiY9lGGUoTEvMK3gj7PfKd5+HTH/t1q3TmrcnVZN6iYiaoghAJOc4xXLF7UwskxC/+Bxm3+LEjBqk3tlksotb86wpBaR2gg+hsgpNspKRuZtrjZfdvN4bIyfgpftvL6isd+nKAlbd9ocsEnVqf24a5KSXOMWDITqVQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Ld2MY9RN; 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="Ld2MY9RN" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E662BC4CEDD; Mon, 20 Jan 2025 12:25:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1737375910; bh=sPS18muDCtBOUW0OqUdtnsEKIul3j7CdK5hJRv/QnHU=; h=Date:Cc:Subject:To:References:From:In-Reply-To:From; b=Ld2MY9RNACM0BYN7MwrUyjoAVkYhMrhcCEizUfuiVE5qyaPmXhg2JMtReY0mBUTfx d6SUtbeydLiYGYHm7emnpVI1C/nyqaUVcM/tcfDmQuMHwA36ydOycWrHdVOdOgVpKX IH8pc1AQ6t3DUZ5/aiv8XOLXeVb60k6LFzOnpjyRlLeEuCFrJnAhtCUsl31MuhTymy AxXExtFNQjVr0gc7QC9NP/OYGi73J1Ogns18MwuHmwxpWuHhhvDBGjRTq3nOCn2rsE uZPn/DQtno8hoLVPDlBz7QFyOp24UePZiZyyWPOeaKUkZ5BfiqAS+UVFPPYO5/AY1P 0a6CJb4Et8xpg== Message-ID: <4270b213-e4f9-46b2-958a-df3dbaaed969@kernel.org> Date: Mon, 20 Jan 2025 20:25:08 +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> Content-Language: en-US From: Chao Yu In-Reply-To: <20250109122755.177926-1-guochunhai@vivo.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit 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)? 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;