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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 52B21E95A87 for ; Sun, 8 Oct 2023 00:53:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234445AbjJHAxZ (ORCPT ); Sat, 7 Oct 2023 20:53:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57974 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234436AbjJHAxH (ORCPT ); Sat, 7 Oct 2023 20:53:07 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A1F6B198B; Sat, 7 Oct 2023 17:49:55 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B3F73C433AD; Sun, 8 Oct 2023 00:49:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1696726195; bh=ZjCh8/FJjF3WMsH6UnPMzA0/YZG7x4p2NFD2leXaqCY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Z0Ermj/lhkC192LLQBKMpD+aS+iS6sLbSsuTYI1PhkgUIBnVVv/blGngyMrlaJk6I 8zhQuY32Y+ziXMcS13xwu1nIRmaDAzTia1Azlmzp06UUTQv6DK+L/aBADLPloI+dcI 4CLcA0httfsX0Rrf820NUdw88XZESH3sUqlimOWjfSeL8IrUB23BiyzycLDjComu+l HP8iwM44QTy1Ci41Ri6+/F77i0KzNSWlymo1SY39EXjprC6KRXJFVi/kf/e3M85ErC mxra3zYVAnWoqwMz2wyikb7thBNS9okHAeQGUzNXYITMbeC4+20tzPq/+KrAqkBeCX LKGPLZvSpgctw== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Chunhai Guo , Jan Kara , Christian Brauner , Sasha Levin , viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org Subject: [PATCH AUTOSEL 5.15 02/10] fs-writeback: do not requeue a clean inode having skipped pages Date: Sat, 7 Oct 2023 20:49:41 -0400 Message-Id: <20231008004950.3768189-2-sashal@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20231008004950.3768189-1-sashal@kernel.org> References: <20231008004950.3768189-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 5.15.134 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org From: Chunhai Guo [ Upstream commit be049c3a088d512187407b7fd036cecfab46d565 ] When writing back an inode and performing an fsync on it concurrently, a deadlock issue may arise as shown below. In each writeback iteration, a clean inode is requeued to the wb->b_dirty queue due to non-zero pages_skipped, without anything actually being written. This causes an infinite loop and prevents the plug from being flushed, resulting in a deadlock. We now avoid requeuing the clean inode to prevent this issue. wb_writeback fsync (inode-Y) blk_start_plug(&plug) for (;;) { iter i-1: some reqs with page-X added into plug->mq_list // f2fs node page-X with PG_writeback filemap_fdatawrite __filemap_fdatawrite_range // write inode-Y with sync_mode WB_SYNC_ALL do_writepages f2fs_write_data_pages __f2fs_write_data_pages // wb_sync_req[DATA]++ for WB_SYNC_ALL f2fs_write_cache_pages f2fs_write_single_data_page f2fs_do_write_data_page f2fs_outplace_write_data f2fs_update_data_blkaddr f2fs_wait_on_page_writeback wait_on_page_writeback // wait for f2fs node page-X iter i: progress = __writeback_inodes_wb(wb, work) . writeback_sb_inodes . __writeback_single_inode // write inode-Y with sync_mode WB_SYNC_NONE . . do_writepages . . f2fs_write_data_pages . . . __f2fs_write_data_pages // skip writepages due to (wb_sync_req[DATA]>0) . . . wbc->pages_skipped += get_dirty_pages(inode) // wbc->pages_skipped = 1 . if (!(inode->i_state & I_DIRTY_ALL)) // i_state = I_SYNC | I_SYNC_QUEUED . total_wrote++; // total_wrote = 1 . requeue_inode // requeue inode-Y to wb->b_dirty queue due to non-zero pages_skipped if (progress) // progress = 1 continue; iter i+1: queue_io // similar process with iter i, infinite for-loop ! } blk_finish_plug(&plug) // flush plug won't be called Signed-off-by: Chunhai Guo Reviewed-by: Jan Kara Message-Id: <20230916045131.957929-1-guochunhai@vivo.com> Signed-off-by: Christian Brauner Signed-off-by: Sasha Levin --- fs/fs-writeback.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index c76537a6826a7..5f0abea107e46 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -1557,10 +1557,15 @@ static void requeue_inode(struct inode *inode, struct bdi_writeback *wb, if (wbc->pages_skipped) { /* - * writeback is not making progress due to locked - * buffers. Skip this inode for now. + * Writeback is not making progress due to locked buffers. + * Skip this inode for now. Although having skipped pages + * is odd for clean inodes, it can happen for some + * filesystems so handle that gracefully. */ - redirty_tail_locked(inode, wb); + if (inode->i_state & I_DIRTY_ALL) + redirty_tail_locked(inode, wb); + else + inode_cgwb_move_to_attached(inode, wb); return; } -- 2.40.1