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 0693C13FEC for ; Mon, 23 Oct 2023 11:06:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="cC+bVK1/" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 77F12C433C9; Mon, 23 Oct 2023 11:06:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1698059206; bh=RJRKMQJsfyazKrEo4MI10c+qkRbxv/5PvauCdd3VAS0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=cC+bVK1/YMm0TnNDPd+diWjsxIGlk04BbGLuAyuTGrdeBbuNXQ+T1cch911Y3ty6w jzHCkq8V6OyTD9+mKkSZNVtCh66vw2TtlTMTq46uhxWQYDQIrAqiW7MNWtZMtgkftm 5LbBfibktOxIPXA+PLXJZAyb3JvcFz6HwpjlZXwI= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Chunhai Guo , Jan Kara , Christian Brauner , Sasha Levin Subject: [PATCH 6.5 100/241] fs-writeback: do not requeue a clean inode having skipped pages Date: Mon, 23 Oct 2023 12:54:46 +0200 Message-ID: <20231023104836.340537783@linuxfoundation.org> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20231023104833.832874523@linuxfoundation.org> References: <20231023104833.832874523@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.5-stable review patch. If anyone has any objections, please let me know. ------------------ 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 aca4b48113945..d532a93e980d7 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -1535,10 +1535,15 @@ 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