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 0CC2AC433EF for ; Thu, 14 Apr 2022 13:49:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1343680AbiDNNuY (ORCPT ); Thu, 14 Apr 2022 09:50:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57624 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1344099AbiDNNaX (ORCPT ); Thu, 14 Apr 2022 09:30:23 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 682821B6; Thu, 14 Apr 2022 06:27:59 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 068286190F; Thu, 14 Apr 2022 13:27:59 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 16B14C385A5; Thu, 14 Apr 2022 13:27:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1649942878; bh=cML5sl7w+/mfiwBUeIfZj6Aya5S1WL48P0FZVHONaYY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=1BlVQJVWMDAg3n7KhnEwCZ7N8fwEMeVA18cT7bbaSaRL/5ywRRsBURdGjYuN3KzGP JitDWKeNUGGn+PrmSkAT3/3LU3iA05Lg/LpdHn4gNKBNoK74b7i59wr31TlUlNQwON +WuXTrxBLwE4fj+DnDcj5JNPjFSA3+72pkyWRDl0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, NeilBrown , Trond Myklebust , Sasha Levin Subject: [PATCH 4.19 295/338] NFS: swap-out must always use STABLE writes. Date: Thu, 14 Apr 2022 15:13:18 +0200 Message-Id: <20220414110847.283683250@linuxfoundation.org> X-Mailer: git-send-email 2.35.2 In-Reply-To: <20220414110838.883074566@linuxfoundation.org> References: <20220414110838.883074566@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: NeilBrown [ Upstream commit c265de257f558a05c1859ee9e3fed04883b9ec0e ] The commit handling code is not safe against memory-pressure deadlocks when writing to swap. In particular, nfs_commitdata_alloc() blocks indefinitely waiting for memory, and this can consume all available workqueue threads. swap-out most likely uses STABLE writes anyway as COND_STABLE indicates that a stable write should be used if the write fits in a single request, and it normally does. However if we ever swap with a small wsize, or gather unusually large numbers of pages for a single write, this might change. For safety, make it explicit in the code that direct writes used for swap must always use FLUSH_STABLE. Signed-off-by: NeilBrown Signed-off-by: Trond Myklebust Signed-off-by: Sasha Levin --- fs/nfs/direct.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c index 41ff316cd6ad..6a4083d550c6 100644 --- a/fs/nfs/direct.c +++ b/fs/nfs/direct.c @@ -888,7 +888,7 @@ static const struct nfs_pgio_completion_ops nfs_direct_write_completion_ops = { */ static ssize_t nfs_direct_write_schedule_iovec(struct nfs_direct_req *dreq, struct iov_iter *iter, - loff_t pos) + loff_t pos, int ioflags) { struct nfs_pageio_descriptor desc; struct inode *inode = dreq->inode; @@ -896,7 +896,7 @@ static ssize_t nfs_direct_write_schedule_iovec(struct nfs_direct_req *dreq, size_t requested_bytes = 0; size_t wsize = max_t(size_t, NFS_SERVER(inode)->wsize, PAGE_SIZE); - nfs_pageio_init_write(&desc, inode, FLUSH_COND_STABLE, false, + nfs_pageio_init_write(&desc, inode, ioflags, false, &nfs_direct_write_completion_ops); desc.pg_dreq = dreq; get_dreq(dreq); @@ -1042,11 +1042,13 @@ ssize_t nfs_file_direct_write(struct kiocb *iocb, struct iov_iter *iter, dreq->iocb = iocb; if (swap) { - requested = nfs_direct_write_schedule_iovec(dreq, iter, pos); + requested = nfs_direct_write_schedule_iovec(dreq, iter, pos, + FLUSH_STABLE); } else { nfs_start_io_direct(inode); - requested = nfs_direct_write_schedule_iovec(dreq, iter, pos); + requested = nfs_direct_write_schedule_iovec(dreq, iter, pos, + FLUSH_COND_STABLE); if (mapping->nrpages) { invalidate_inode_pages2_range(mapping, -- 2.35.1