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 195AC13B5AE for ; Wed, 18 Mar 2026 04:02:44 +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=1773806565; cv=none; b=n4z5nK/wH1wr8JSzSdGNcd6yc98xS+uPVz2wMwqOHPWZgb2kTswVjznauP/ClYG2ZMRs8eUJbJ5s5CCIeByOvQPqe2CoiqbFaEkhRBPhHY1XIZi/yqzchb8oJVBzbNHtWzN96buEdJuXxKI1xqIopcOUop7taFscj8/ETfRiO4M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773806565; c=relaxed/simple; bh=BKatsPyY3aKXXSeiP3h6+vMW0sNigVveIkwKUJixiiI=; h=Message-ID:Date:MIME-Version:Cc:Subject:To:References:From: In-Reply-To:Content-Type; b=NZUY6XD8tvH+GAzgOZYRxPJZfQa1tHmzRjDvM3B3bavpKaRSEe3xyvUytwfQN/Cf+J97t0FYf0Gzh3s1JmZxMRY/QkDmi/0o8queH7eVwQ/BNkP08ewRRg5uXLK/ZSDrJMPCRBGLSBdASjKFkZTfl5QeZsvdeL8u3hxmVIAWSX4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=tUCJ5U4N; 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="tUCJ5U4N" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A665CC19421; Wed, 18 Mar 2026 04:02:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1773806564; bh=BKatsPyY3aKXXSeiP3h6+vMW0sNigVveIkwKUJixiiI=; h=Date:Cc:Subject:To:References:From:In-Reply-To:From; b=tUCJ5U4NJVAdVk/VQVqmwet6RpWNn8ZywfspFGVyO4omYYlSBqHThoTRFEPJdsFBl 8LIjaHYGUCjnv46fePGxpp6MDJMqZYRv5vp244a1mA3poy+yivsopc/HgfSSXL2aO5 6EZEmzJnPdHZLpS3ngPbqCySsl/o0rcohXia0zMUMy0qvQhn8+NO8q0eR/Nu3Dr1zm zQ3iM/cCOjEqiQK/rZwueiLm27Oikaw6WEDHZ37XBnnKLkbZGOw/JSJCrHTV+9c8oM hz4/fOrz5Wd+2LL9u66JlIzfjoFrPnd1NZsAKINPO6VaVvInxwNc4LaulshRUIjCrX UGyBmDo2W0iMA== Message-ID: <97fbb139-55a8-493d-b804-c8234d86e677@kernel.org> Date: Wed, 18 Mar 2026 12:02:39 +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-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, kernel-team@android.com, Daeho Jeong Subject: Re: [f2fs-dev] [PATCH v3] f2fs: fix to freeze GC and discard threads quickly To: Daeho Jeong References: <20260316185954.2185806-1-daeho43@gmail.com> Content-Language: en-US From: Chao Yu In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 2026/3/18 00:15, Daeho Jeong wrote: > On Mon, Mar 16, 2026 at 6:56 PM Chao Yu wrote: >> >> On 2026/3/17 02:59, Daeho Jeong wrote: >>> From: Daeho Jeong >>> >>> Suspend can fail if kernel threads do not freeze for a while. >>> f2fs_gc and f2fs_discard threads can perform long-running operations >>> that prevent them from reaching a freeze point in a timely manner. >>> >>> This patch adds explicit freezing checks in the following locations: >>> 1. f2fs_gc: Added a check at the 'retry' label to exit the loop quickly >>> if freezing is requested, especially during heavy GC rounds. >>> 2. __issue_discard_cmd: Added a 'suspended' flag to break both inner and >>> outer loops during discard command issuance if freezing is detected >>> after at least one command has been issued. >>> 3. __issue_discard_cmd_orderly: Added a similar check for orderly discard >>> to ensure responsiveness. >>> >>> These checks ensure that the threads release locks safely and enter the >>> frozen state. >>> >>> Signed-off-by: Daeho Jeong >>> --- >>> v3: removed unnecessary suspended check >>> v2: add freezing check in do_garbage_collect() >>> --- >>> fs/f2fs/gc.c | 10 ++++++++++ >>> fs/f2fs/segment.c | 12 +++++++++++- >>> 2 files changed, 21 insertions(+), 1 deletion(-) >>> >>> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c >>> index 246496fbe5e5..2305f16cbabb 100644 >>> --- a/fs/f2fs/gc.c >>> +++ b/fs/f2fs/gc.c >>> @@ -1889,12 +1889,18 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi, >>> sbi->next_victim_seg[gc_type] = >>> (cur_segno + 1 < sec_end_segno) ? >>> cur_segno + 1 : NULL_SEGNO; >>> + >>> + if (unlikely(freezing(current))) { >>> + folio_put_refs(sum_folio, 2); >>> + goto stop; >> >> Do we need to return EBUSY or something like that to indicate GC was >> interrupted? > > In the case of do_garbage_collect(), it is originally designed to stop before > cleaning the entire section depending on the migration_window size or > zoned GC operations, and it returns the count of segments reclaimed until > that point. Therefore, returning the segment count reclaimed up to the > moment of suspension seems more consistent with the existing behavior. > If we return an error instead, the caller might miss the count of segments > that were actually reclaimed. It makes sense. In addition, I think freezing(current) will only be true in context of gc thread, for such background migration condition, we don't care the error number. Thanks, > >> >>> + } >>> } >>> next_block: >>> folio_put_refs(sum_folio, 2); >>> segno = block_end_segno; >>> } >>> >>> +stop: >>> if (submitted) >>> f2fs_submit_merged_write(sbi, data_type); >>> >>> @@ -1968,6 +1974,10 @@ int f2fs_gc(struct f2fs_sb_info *sbi, struct f2fs_gc_control *gc_control) >>> goto stop; >>> } >>> retry: >>> + if (unlikely(freezing(current))) { >>> + ret = 0; >> >> Ditto. > > For f2fs_gc(), if we return -EBUSY, the caller might perceive it as a > situation where no more victims > can be selected. This could lead to an issue where the idle time is > incorrectly extended under the > "no GC" condition. > >> >> Thanks, >> >>> + goto stop; >>> + } >>> ret = __get_victim(sbi, &segno, gc_type, gc_control->one_time); >>> if (ret) { >>> /* allow to search victim from sections has pinned data */ >>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c >>> index e9b6d774b985..0c4fb4270185 100644 >>> --- a/fs/f2fs/segment.c >>> +++ b/fs/f2fs/segment.c >>> @@ -1606,6 +1606,9 @@ static void __issue_discard_cmd_orderly(struct f2fs_sb_info *sbi, >>> if (dc->state != D_PREP) >>> goto next; >>> >>> + if (*issued > 0 && unlikely(freezing(current))) >>> + break; >>> + >>> if (dpolicy->io_aware && !is_idle(sbi, DISCARD_TIME)) { >>> io_interrupted = true; >>> break; >>> @@ -1645,6 +1648,7 @@ static int __issue_discard_cmd(struct f2fs_sb_info *sbi, >>> struct blk_plug plug; >>> int i, issued; >>> bool io_interrupted = false; >>> + bool suspended = false; >>> >>> if (dpolicy->timeout) >>> f2fs_update_time(sbi, UMOUNT_DISCARD_TIMEOUT); >>> @@ -1675,6 +1679,11 @@ static int __issue_discard_cmd(struct f2fs_sb_info *sbi, >>> list_for_each_entry_safe(dc, tmp, pend_list, list) { >>> f2fs_bug_on(sbi, dc->state != D_PREP); >>> >>> + if (issued > 0 && unlikely(freezing(current))) { >>> + suspended = true; >>> + break; >>> + } >>> + >>> if (dpolicy->timeout && >>> f2fs_time_over(sbi, UMOUNT_DISCARD_TIMEOUT)) >>> break; >>> @@ -1694,7 +1703,8 @@ static int __issue_discard_cmd(struct f2fs_sb_info *sbi, >>> next: >>> mutex_unlock(&dcc->cmd_lock); >>> >>> - if (issued >= dpolicy->max_requests || io_interrupted) >>> + if (issued >= dpolicy->max_requests || io_interrupted || >>> + suspended) >>> break; >>> } >>> >>