From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.sourceforge.net (lists.sourceforge.net [216.105.38.7]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 1513CF36C2E for ; Mon, 20 Apr 2026 07:35:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.sourceforge.net; s=beta; h=Content-Type:Content-Transfer-Encoding:Cc: Reply-To:From:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:Subject:In-Reply-To:References:To:MIME-Version:Date: Message-ID:Sender:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=PWgWcS+zVc96h4D2+AjjKTu1UMJjArahzXEXQbJi0/c=; b=isX813dlP3m6su1Wn80YilKh3m Jwq0OfVQ+uD7wE0ORT5DWSVBZsta3/6niPBtA1HHGmEzeYbYJnmXUBcCIKsieTIR6lT1+dh86wMk+ JX+1HRVg2WvM8FXK7IfUbPpI7fu6l+8r7KEN8281kXcpLq+YTJ+Q9GUGGB3VJVce7cwE=; Received: from [127.0.0.1] (helo=sfs-ml-4.v29.lw.sourceforge.com) by sfs-ml-4.v29.lw.sourceforge.com with esmtp (Exim 4.95) (envelope-from ) id 1wEjAV-0000gp-1r; Mon, 20 Apr 2026 07:35:43 +0000 Received: from [172.30.29.66] (helo=mx.sourceforge.net) by sfs-ml-4.v29.lw.sourceforge.com with esmtps (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.95) (envelope-from ) id 1wEjAT-0000gg-Qg for linux-f2fs-devel@lists.sourceforge.net; Mon, 20 Apr 2026 07:35:41 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sourceforge.net; s=x; h=Content-Transfer-Encoding:Content-Type:In-Reply-To: From:References:To:Subject:Cc:MIME-Version:Date:Message-ID:Sender:Reply-To: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=AQ6nR96MlJ9E70p3Pjy4XTh/JX7e0wc34rlhcCrGKg4=; b=fA7ulqXI+yQ5bvoBfXCu9Wmmgy rhr9H8lHzDutJqc3nrZXqmpITrebmlfWOWxiadOdNVg6pgIxjhgPuK/G/iStKA6iLGi0DjsMZxIXc qut+coicpiF5jP+QPUPgR73LtYCKep5Bf57pmZ8+wU6FJJigPskXM4WTTPLZOQf4dIto=; DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sf.net; s=x ; h=Content-Transfer-Encoding:Content-Type:In-Reply-To:From:References:To: Subject:Cc:MIME-Version:Date:Message-ID:Sender:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=AQ6nR96MlJ9E70p3Pjy4XTh/JX7e0wc34rlhcCrGKg4=; b=XVDVPH0W/wS4OC7k/bKgSNqWC/ EopJVTq8pNKrASLKDHG6bjr5BMT2cX+7aH7UMbpO/WSeHaj0xIEfTMYtqH0gvjSab31rzbm8tSsV5 fvp4+QUN9eiFclE2e9x655UexLUVnFYcRRFwI+BrKF0YeQEHxDDDtSRcUUuJhD7uevNg=; Received: from tor.source.kernel.org ([172.105.4.254]) by sfi-mx-2.v28.lw.sourceforge.com with esmtps (TLS1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.95) id 1wEjAT-00017O-2q for linux-f2fs-devel@lists.sourceforge.net; Mon, 20 Apr 2026 07:35:41 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 68CD260103; Mon, 20 Apr 2026 07:35:30 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id AB894C19425; Mon, 20 Apr 2026 07:35:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1776670530; bh=wWspKhQXTOFZHp5pCXuza2DronRfDj4EXc/yRmaytgg=; h=Date:Cc:Subject:To:References:From:In-Reply-To:From; b=Q0Uj3Y923EnAuoCMYufBwwL9gvkS61xySjzUDSnXkFGxwtiRFCsLhrjfbXMa1fuuw OAf7ZYDtX+PH4IhuiJhGvfZy6zgV7p28pkZrySfn73/xMSK76nywAnr2AmHjQ0W8hd Tig87zby8ZqaRaePb6XJGpTHAJ6vXQF8GZ6srl4rh0ggv8HS28BjAzuFt3S2MkZBXM bopQczJgyvE+5vUfqJTj7ulara1eNR482FK95uQk8W9yl+UASDK3yXRLUKbEuziA4M ZJMXfHJgbnkv30MuHVSH0TvbNz/pDLw6us2bUvYp7nGBYAehZz9P54qhSkcFbaFdRh 0nfeKKc3VEFRQ== Message-ID: <607d2d34-9d58-42d1-8436-e85d9c73eb7a@kernel.org> Date: Mon, 20 Apr 2026 15:35:29 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird To: ruipengqi , jaegeuk@kernel.org References: <20260325133749.1053541-1-ruipengqi3@gmail.com> Content-Language: en-US In-Reply-To: <20260325133749.1053541-1-ruipengqi3@gmail.com> X-Headers-End: 1wEjAT-00017O-2q Subject: Re: [f2fs-dev] [PATCH] f2fs: fix potential deadlock in f2fs_balance_fs() X-BeenThere: linux-f2fs-devel@lists.sourceforge.net X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , From: Chao Yu via Linux-f2fs-devel Reply-To: Chao Yu Cc: linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net Hi Ruipeng, Sorry, I missed your patch. On 3/25/2026 9:37 PM, ruipengqi wrote: > From: Ruipeng Qi > > When the f2fs filesystem space is nearly exhausted, we encounter deadlock > issues as below: > > INFO: task A:1890 blocked for more than 120 seconds. > Tainted: G O 6.12.41-g3fe07ddf05ab #1 > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > task:A state:D stack:0 pid:1890 tgid:1626 ppid:1153 flags:0x00000204 > Call trace: > __switch_to+0xf4/0x158 > __schedule+0x27c/0x908 > schedule+0x3c/0x118 > io_schedule+0x44/0x68 > folio_wait_bit_common+0x174/0x370 > folio_wait_bit+0x20/0x38 > folio_wait_writeback+0x54/0xc8 > truncate_inode_partial_folio+0x70/0x1e0 > truncate_inode_pages_range+0x1b0/0x450 > truncate_pagecache+0x54/0x88 > f2fs_file_write_iter+0x3e8/0xb80 > do_iter_readv_writev+0xf0/0x1e0 > vfs_writev+0x138/0x2c8 > do_writev+0x88/0x130 > __arm64_sys_writev+0x28/0x40 > invoke_syscall+0x50/0x120 > el0_svc_common.constprop.0+0xc8/0xf0 > do_el0_svc+0x24/0x38 > el0_svc+0x30/0xf8 > el0t_64_sync_handler+0x120/0x130 > el0t_64_sync+0x190/0x198 > > INFO: task kworker/u8:11:2680853 blocked for more than 120 seconds. > Tainted: G O 6.12.41-g3fe07ddf05ab #1 > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > task:kworker/u8:11 state:D stack:0 pid:2680853 tgid:2680853 ppid:2 flags:0x00000208 > Workqueue: writeback wb_workfn (flush-254:0) > Call trace: > __switch_to+0xf4/0x158 > __schedule+0x27c/0x908 > schedule+0x3c/0x118 > io_schedule+0x44/0x68 > folio_wait_bit_common+0x174/0x370 > __filemap_get_folio+0x214/0x348 > pagecache_get_page+0x20/0x70 > f2fs_get_read_data_page+0x150/0x3e8 > f2fs_get_lock_data_page+0x2c/0x160 > move_data_page+0x50/0x478 > do_garbage_collect+0xd38/0x1528 > f2fs_gc+0x240/0x7e0 > f2fs_balance_fs+0x1a0/0x208 > f2fs_write_single_data_page+0x6e4/0x730 //0xfffffe0d6ca08300 > f2fs_write_cache_pages+0x378/0x9b0 > f2fs_write_data_pages+0x2e4/0x388 > do_writepages+0x8c/0x2c8 > __writeback_single_inode+0x4c/0x498 > writeback_sb_inodes+0x234/0x4a8 > __writeback_inodes_wb+0x58/0x118 > wb_writeback+0x2f8/0x3c0 > wb_workfn+0x2c4/0x508 > process_one_work+0x180/0x408 > worker_thread+0x258/0x368 > kthread+0x118/0x128 > ret_from_fork+0x10/0x200 > > INFO: task kworker/u8:8:2641297 blocked for more than 120 seconds. > Tainted: G O 6.12.41-g3fe07ddf05ab #1 > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > task:kworker/u8:8 state:D stack:0 pid:2641297 tgid:2641297 ppid:2 flags:0x00000208 > Workqueue: writeback wb_workfn (flush-254:0) > Call trace: > __switch_to+0xf4/0x158 > __schedule+0x27c/0x908 > rt_mutex_schedule+0x30/0x60 > __rt_mutex_slowlock_locked.constprop.0+0x460/0x8a8 > rwbase_write_lock+0x24c/0x378 > down_write+0x1c/0x30 > f2fs_balance_fs+0x184/0x208 > f2fs_write_inode+0xf4/0x328 > __writeback_single_inode+0x370/0x498 > writeback_sb_inodes+0x234/0x4a8 > __writeback_inodes_wb+0x58/0x118 > wb_writeback+0x2f8/0x3c0 > wb_workfn+0x2c4/0x508 > process_one_work+0x180/0x408 > worker_thread+0x258/0x368 > kthread+0x118/0x128 > ret_from_fork+0x10/0x20 > > INFO: task B:1902 blocked for more than 120 seconds. > Tainted: G O 6.12.41-g3fe07ddf05ab #1 > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > task:B state:D stack:0 pid:1902 tgid:1626 ppid:1153 flags:0x0000020c > Call trace: > __switch_to+0xf4/0x158 > __schedule+0x27c/0x908 > rt_mutex_schedule+0x30/0x60 > __rt_mutex_slowlock_locked.constprop.0+0x460/0x8a8 > rwbase_write_lock+0x24c/0x378 > down_write+0x1c/0x30 > f2fs_balance_fs+0x184/0x208 > f2fs_map_blocks+0x94c/0x1110 > f2fs_file_write_iter+0x228/0xb80 > do_iter_readv_writev+0xf0/0x1e0 > vfs_writev+0x138/0x2c8 > do_writev+0x88/0x130 > __arm64_sys_writev+0x28/0x40 > invoke_syscall+0x50/0x120 > el0_svc_common.constprop.0+0xc8/0xf0 > do_el0_svc+0x24/0x38 > el0_svc+0x30/0xf8 > el0t_64_sync_handler+0x120/0x130 > el0t_64_sync+0x190/0x198 > > INFO: task sync:2769849 blocked for more than 120 seconds. > Tainted: G O 6.12.41-g3fe07ddf05ab #1 > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > task:sync state:D stack:0 pid:2769849 tgid:2769849 ppid:736 flags:0x0000020c > Call trace: > __switch_to+0xf4/0x158 > __schedule+0x27c/0x908 > schedule+0x3c/0x118 > wb_wait_for_completion+0xb0/0xe8 > sync_inodes_sb+0xc8/0x2b0 > sync_inodes_one_sb+0x24/0x38 > iterate_supers+0xa8/0x138 > ksys_sync+0x54/0xc8 > __arm64_sys_sync+0x18/0x30 > invoke_syscall+0x50/0x120 > el0_svc_common.constprop.0+0xc8/0xf0 > do_el0_svc+0x24/0x38 > el0_svc+0x30/0xf8 > el0t_64_sync_handler+0x120/0x130 > el0t_64_sync+0x190/0x198 > > The root cause is a potential deadlock between the following tasks: > > kworker/u8:11 Thread A > - f2fs_write_single_data_page > - f2fs_do_write_data_page > - folio_start_writeback(X) > - f2fs_outplace_write_data > - bio_add_folio(X) > - folio_unlock(X) > - truncate_inode_pages_range > - __filemap_get_folio(X, FGP_LOCK) > - truncate_inode_partial_folio(X) > - folio_wait_writeback(X) > - f2fs_balance_fs > - f2fs_gc > - do_garbage_collect > - move_data_page > - f2fs_get_lock_data_page > - __filemap_get_folio(X, FGP_LOCK) > > Both threads try to access folio X. Thread A holds the lock but waits > for writeback, while kworker waits for the lock. This causes a deadlock. > > Other threads also enter D state, waiting for locks such as gc_lock and > writepages. > > To avoid this potential deadlock, always call f2fs_submit_merged_write > before triggering f2fs_gc in f2fs_balance_fs. > > Signed-off-by: Ruipeng Qi > --- > fs/f2fs/segment.c | 14 ++++++++++++++ > 1 file changed, 14 insertions(+) > > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c > index 6a97fe76712b..b58299e49c23 100644 > --- a/fs/f2fs/segment.c > +++ b/fs/f2fs/segment.c > @@ -454,6 +454,20 @@ void f2fs_balance_fs(struct f2fs_sb_info *sbi, bool need) > io_schedule(); > finish_wait(&sbi->gc_thread->fggc_wq, &wait); > } else { > + > + /* > + * Before triggering foreground GC, submit all cached DATA > + * write bios. During writeback, pages may be added to > + * write_io[DATA].bio with PG_writeback set but the bio not > + * yet submitted. If GC's move_data_page() blocks on > + * __folio_lock() for such a folio, and the lock holder waits > + * for PG_writeback to clear via VFS folio_wait_writeback() > + * neither thread can make progress. Flushing here ensures > + * the bio completion callback can clear PG_writeback. > + */ > + > + f2fs_submit_merged_write(sbi, DATA); Do we need to call f2fs_submit_merged_ipu_write(sbi, bio, NULL) to commit cached IPU folios as well? Not sure, this race condition will happen for node folio. Thanks, > + > struct f2fs_gc_control gc_control = { > .victim_segno = NULL_SEGNO, > .init_gc_type = f2fs_sb_has_blkzoned(sbi) ? _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel