From nobody Sat Feb 7 19:50:54 2026 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 84225264614 for ; Wed, 21 May 2025 11:56:49 +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=1747828609; cv=none; b=M1OU4n4MspgNFvNg5aCT50CFC5eWHzix4HQ86+VLtESvadgebionUfhi/ttVBTj/maZUlW8J9Tm+hebMZwEw0O1FLk56R3R+KA7jwEiGN7MoBTw7SW0m1kJ659t9gN+YD9bkbUo4q9kCmiYwMhT435JASO0DdpIG3EmtfaOSxTI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747828609; c=relaxed/simple; bh=32nBK1uDQNJmr5ueHl6ztx09emDA9JhlP9K7dSuMnWE=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=SWCRICkBHolN28+Mlz3AjgSWlqQ1sH5dCKefK66F0ihaaE1WFYz1658JmsFJZhScSq3IaNP6/zDmxjfOAYJffpSnU0JRDPMHZgssUh+z5UBy4e/iEKrvLdfdO5/VFLpDqpTo1+Uq64A3+OryOZOoDIykhaEqrn8mD3nhZzJaC9k= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Oug/Ubzs; 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="Oug/Ubzs" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 926CAC4CEE4; Wed, 21 May 2025 11:56:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1747828609; bh=32nBK1uDQNJmr5ueHl6ztx09emDA9JhlP9K7dSuMnWE=; h=From:To:Cc:Subject:Date:From; b=Oug/UbzsruDwihb3MtFAq6Bb7AJ9ArCPNvd0/swPUDl3nimBGnWm5LK0H8DypWeTv HsypXXpqcpD5CT+XZuMR5IDNs8uHoagLKA8jLIAomYMvoc0EEPDEZh9PtXGLYCw0Nv mn5m1SCubYoUf9RpR6SqCr/6NKNCmw9npIINo9v5LKLWldtMElcJEaI6Vvh+fv9LpR 39EIW/qjqimE0jwfy3NPJNw98gpFN3z9YUq07iVYLA25iP2csXbamur2z/VYXJPfO7 M9SnQpSflBzFGHslcBruawj6YXqLUL86iztaR99iP1G4GiL5IxfcaHWm7XqVE6sf0o 5trY5aAOP+Gsg== From: Chao Yu To: jaegeuk@kernel.org Cc: linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, Chao Yu , syzbot+aa5bb5f6860e08a60450@syzkaller.appspotmail.com, Qi Han Subject: [PATCH v2] f2fs: fix to skip f2fs_balance_fs() if checkpoint is disabled Date: Wed, 21 May 2025 19:56:35 +0800 Message-ID: <20250521115635.829744-1-chao@kernel.org> X-Mailer: git-send-email 2.49.0.1143.g0be31eac6b-goog Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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 t= ask_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=3Ddisable, 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 =3D SB_FREEZE_WRITE; - sb_wait_write(sb, SB_FREEZE_WRITE); - if (sbi->sb->s_writers.frozen >=3D 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.a00a0220.29bc26.0= 289.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 nee= d) if (need && excess_cached_nats(sbi)) f2fs_balance_fs_bg(sbi, false); =20 + if (unlikely(is_sbi_flag_set(sbi, SBI_CP_DISABLED))) + return; if (!f2fs_is_checkpoint_ready(sbi)) return; =20 --=20 2.49.0