From nobody Sun Feb 8 01:15:27 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 5B44C1C6FF6 for ; Fri, 23 May 2025 03:25:49 +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=1747970750; cv=none; b=W+n5srVTcIdTLgufgbyiIf/ob1c5K/nk2JGY4ekSULiRPpIPcoxBiIA7Yc1Gvb8wqL8xvsniW465TdXe0mv0U0sAHCSlsHv3tF5SPmttRuGpd0HSiCAbArb8QdVqLN/tzUn2cEyH5BaNUBBiUKsvZbImV9QFgzOTnSgB/uhPwx8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747970750; c=relaxed/simple; bh=zs8r39vbFN2or9MqJTpefToKt3xi9idBEwDckvz2KwE=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=IfUGitk5TLzLnHpOAH5+F1O5N7ATzNSZ1oioJ9Z6+NLN9NSbvhZV6v731RQHiromxhIBkYu26clu/1ItWbG2e6Tnri5Du3iWRhZ2COgbH70yNHqcQ+zYQ1kRocQYPEWCSBkLYKSwbPUTNuguzw34SLCH6lyxKQicQaq8CzObnB0= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=RDLkN5U8; 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="RDLkN5U8" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A0021C4CEE9; Fri, 23 May 2025 03:25:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1747970749; bh=zs8r39vbFN2or9MqJTpefToKt3xi9idBEwDckvz2KwE=; h=From:To:Cc:Subject:Date:From; b=RDLkN5U8S0h0uFcNamFboMXudFbJhQc8QAf3cr+uRhghhFNDHhun8aEUAm1nP4Qz2 rFZSWF2yCW026/4xDW44AG2ngCgkP/dEPvr7Ro4zwH2M3PYk1FgSA/rvBu0AJBSXfS FxFI+l0dnWuS6VkcIRREzrs7uhqndFZrunEtPFhoQgMMYIMs+Vjmw0hRLl7jJOTvuo 3S1TkRVeVBI3uAK4ppsodeKDJl67+lQMUl3jCY4uGtjA2b2ofyfkE9Gwvai8Fzox4k duY0BuLGywslGToY01i6pmyX4xt2Tq/Kvll+2l+zLfGBr2p7xjRosazBI8jdcIuk9a a92XCKLuQUV/Q== 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 v3] f2fs: fix to skip f2fs_balance_fs() if checkpoint is disabled Date: Fri, 23 May 2025 11:25:45 +0800 Message-ID: <20250523032545.1392641-1-chao@kernel.org> X-Mailer: git-send-email 2.49.0.1151.ga128411c76-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" Syzbot reports a f2fs bug as below: 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 the testcase mounts f2fs image w/ gc_merge,checkpoint=3Ddisable, so dea= dloop will happen through below race condition: - 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 such deadloop issue. Meanwhile let's remove f2fs_is_checkpoint_ready() check condition in f2fs_balance_fs(), since it's redundant, due to the main logic in the function is to check: a) whether checkpoint is disabled b) there is enough free segments f2fs_balance_fs() still has all logics after f2fs_is_checkpoint_ready()'s removal. 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 Reviewed-by: Zhiguo Niu --- v3: - clean up the codes fs/f2fs/segment.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c index 5ff0111ed974..24b4bb2a4b9b 100644 --- a/fs/f2fs/segment.c +++ b/fs/f2fs/segment.c @@ -433,7 +433,7 @@ 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 (!f2fs_is_checkpoint_ready(sbi)) + if (unlikely(is_sbi_flag_set(sbi, SBI_CP_DISABLED))) return; =20 /* --=20 2.49.0