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 B01CE2DCBE7 for ; Fri, 23 May 2025 02:32:53 +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=1747967573; cv=none; b=r/ppGFcd90MSD2A0JTfRt3ZVrYPCqGPP1ho4DYFeF8MQFFqLwwgwY+P27dKe3ErlEsO8dOGBmEhQYh7vj9nXt8kvHvTkG93g1auz/2aejphSXcfaNm/gOlFIjc3XW7h0lfShRbCDkOoIvN2Y0wjrj6NmOz/NrJkED1OxrcDbedU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747967573; c=relaxed/simple; bh=S25lebnZRW5zzcfOg+loS2fbdOdPCUzd3TChisW/CfM=; h=Message-ID:Date:MIME-Version:Cc:Subject:To:References:From: In-Reply-To:Content-Type; b=A7mbZkwOwQaMUMHXmM5YzSsqdmYFC8o3eGlnSU4SqFu5F0q0anHki03aDtzO9f2rVrwH9C6y8C+U9ic1AuFa3z8SL/j6OpVcTpLeJL26dbZielQCPgjX9vH6fy7RlUWvqeebwDl8GxqI8FiilkQOowOyk8fRnytKatIu61uTdYw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=F70IWq7d; 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="F70IWq7d" Received: by smtp.kernel.org (Postfix) with ESMTPSA id ACEDEC4CEE4; Fri, 23 May 2025 02:32:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1747967573; bh=S25lebnZRW5zzcfOg+loS2fbdOdPCUzd3TChisW/CfM=; h=Date:Cc:Subject:To:References:From:In-Reply-To:From; b=F70IWq7dbwv1hU8ShOf7gZi/CeN0tFvoDF/xdoDjSTCg7r69c/Nt/aZXOj63N0ij6 EsTNnnsgvIGGihMY7zUF3qyupf5ueE3KRoR0fr4rXRjgahIQmOM85ZWuMF3CsmcSsl PACw7y/5qOob1AoSrjQvhQmhqzo84vhUsN3AwDgKjXOiCzLORdjAkUw0EMOYXEA9J7 D090s/p8cjd12xL6xZf+uYZ8/54BLYTuPVCdfW8D76FPtHfq41zWbh0wk5ARVTo4Df ROP1ePaGxKlyCO0NFHJanemjV1dV7+MGBSSuw/Xvf440cMwssyrOhVKyBclXAM1lkP ZA4j77cZtlZPw== Message-ID: <6c51b7aa-8caa-4dae-b079-01ea8571599b@kernel.org> Date: Fri, 23 May 2025 10:32:49 +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, jaegeuk@kernel.org, syzbot+aa5bb5f6860e08a60450@syzkaller.appspotmail.com, Qi Han , linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net Subject: Re: [f2fs-dev] [PATCH v2] f2fs: fix to skip f2fs_balance_fs() if checkpoint is disabled To: Zhiguo Niu References: <20250521115635.829744-1-chao@kernel.org> Content-Language: en-US From: Chao Yu In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 5/23/25 09:39, Zhiguo Niu wrote: > Chao Yu via Linux-f2fs-devel > 于2025年5月21日周三 20:02写道： >> >> INFO: task syz-executor328:5856 blocked for more than 144 seconds. >> Not tainted 6.15.0-rc6-syzkaller-00208-g3c21441eeffc #0 >> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. >> task:syz-executor328 state:D stack:24392 pid:5856 tgid:5832 ppid:5826 task_flags:0x400040 flags:0x00004006 >> Call Trace: >> >> context_switch kernel/sched/core.c:5382 [inline] >> __schedule+0x168f/0x4c70 kernel/sched/core.c:6767 >> __schedule_loop kernel/sched/core.c:6845 [inline] >> schedule+0x165/0x360 kernel/sched/core.c:6860 >> io_schedule+0x81/0xe0 kernel/sched/core.c:7742 >> f2fs_balance_fs+0x4b4/0x780 fs/f2fs/segment.c:444 >> f2fs_map_blocks+0x3af1/0x43b0 fs/f2fs/data.c:1791 >> f2fs_expand_inode_data+0x653/0xaf0 fs/f2fs/file.c:1872 >> f2fs_fallocate+0x4f5/0x990 fs/f2fs/file.c:1975 >> vfs_fallocate+0x6a0/0x830 fs/open.c:338 >> ioctl_preallocate fs/ioctl.c:290 [inline] >> file_ioctl fs/ioctl.c:-1 [inline] >> do_vfs_ioctl+0x1b8f/0x1eb0 fs/ioctl.c:885 >> __do_sys_ioctl fs/ioctl.c:904 [inline] >> __se_sys_ioctl+0x82/0x170 fs/ioctl.c:892 >> do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] >> do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94 >> entry_SYSCALL_64_after_hwframe+0x77/0x7f >> >> The root cause is after commit 84b5bb8bf0f6 ("f2fs: modify >> f2fs_is_checkpoint_ready logic to allow more data to be written with the >> CP disable"), we will get chance to allow f2fs_is_checkpoint_ready() to >> return true once below conditions are all true: >> 1. checkpoint is disabled >> 2. there are not enough free segments >> 3. there are enough free blocks >> >> Then it will cause f2fs_balance_fs() to trigger foreground GC. >> >> void f2fs_balance_fs(struct f2fs_sb_info *sbi, bool need) >> ... >> if (!f2fs_is_checkpoint_ready(sbi)) >> return; >> >> And it mounts f2fs image w/ gc_merge,checkpoint=disable, so below deadloop >> will happen: >> >> - f2fs_do_shutdown - vfs_fallocate - gc_thread_func >> - file_start_write >> - __sb_start_write(SB_FREEZE_WRITE) >> - f2fs_fallocate >> - f2fs_expand_inode_data >> - f2fs_map_blocks >> - f2fs_balance_fs >> - prepare_to_wait >> - wake_up(gc_wait_queue_head) >> - io_schedule >> - bdev_freeze >> - freeze_super >> - sb->s_writers.frozen = SB_FREEZE_WRITE; >> - sb_wait_write(sb, SB_FREEZE_WRITE); >> - if (sbi->sb->s_writers.frozen >= SB_FREEZE_WRITE) continue; >> : cause deadloop >> >> This patch fix to add check condition in f2fs_balance_fs(), so that if >> checkpoint is disabled, we will just skip trigger foreground GC to >> avoid above deadloop issue. >> >> Reported-by: syzbot+aa5bb5f6860e08a60450@syzkaller.appspotmail.com >> Closes: https://lore.kernel.org/linux-f2fs-devel/682d743a.a00a0220.29bc26.0289.GAE@google.com >> Fixes: 84b5bb8bf0f6 ("f2fs: modify f2fs_is_checkpoint_ready logic to allow more data to be written with the CP disable") >> Cc: Qi Han >> Signed-off-by: Chao Yu >> --- >> v2: >> - add missing Closes line >> - fix to use git commit description style >> >> fs/f2fs/segment.c | 2 ++ >> 1 file changed, 2 insertions(+) >> >> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c >> index 5ff0111ed974..19b716fda72a 100644 >> --- a/fs/f2fs/segment.c >> +++ b/fs/f2fs/segment.c >> @@ -433,6 +433,8 @@ void f2fs_balance_fs(struct f2fs_sb_info *sbi, bool need) >> if (need && excess_cached_nats(sbi)) >> f2fs_balance_fs_bg(sbi, false); >> >> + if (unlikely(is_sbi_flag_set(sbi, SBI_CP_DISABLED))) >> + return; >> if (!f2fs_is_checkpoint_ready(sbi)) >> return; > Hi Chao, > When I read this patch, I feel that it is somewhat redundant with the > following checking about SBI_CP_DISABLED in f2fs_is_checkpoint_ready. > Can we reorganize these checks for the f2fs_balance_fs case? Zhiguo, Oh, I agreed. I think we can just use is_sbi_flag_set(sbi, SBI_CP_DISABLED) instead of f2fs_is_checkpoint_ready() here, let me revise it in v3. - if (!f2fs_is_checkpoint_ready(sbi)) + if (unlikely(is_sbi_flag_set(sbi, SBI_CP_DISABLED))) Thanks, > This will make the code easier to read and understand. > thanks! >> >> -- >> 2.49.0 >> >> >> >> _______________________________________________ >> Linux-f2fs-devel mailing list >> Linux-f2fs-devel@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel