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 EB428C433F5 for ; Tue, 12 Apr 2022 07:45:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344630AbiDLHp3 (ORCPT ); Tue, 12 Apr 2022 03:45:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58528 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1352385AbiDLHX5 (ORCPT ); Tue, 12 Apr 2022 03:23:57 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AD61749C94; Mon, 11 Apr 2022 23:59:55 -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 ams.source.kernel.org (Postfix) with ESMTPS id 3BF0DB81B4F; Tue, 12 Apr 2022 06:59:54 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8C152C385A1; Tue, 12 Apr 2022 06:59:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1649746792; bh=AbrsBm56ExWgKrY6ihV1qtgPDJhwjQAJjiPmD0okSmc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=yAH4BVsszc88HVE4raVApWaaZsZgQvW6ftqoYY+AdUt1vdHxnmRax6lkA45e84ggL XlmUJ4yLI9x6RXzXlxP7i6gZpjrV6D8uDWQsrx9pFk1pP7uVS+hjeC/SvsNtOLlGmR T4OKfNBUQy1KHlLIv5tOutxTicpdxs3sV8FXXPYY= 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 5.16 133/285] SUNRPC/xprt: async tasks mustnt block waiting for memory Date: Tue, 12 Apr 2022 08:29:50 +0200 Message-Id: <20220412062947.504783605@linuxfoundation.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220412062943.670770901@linuxfoundation.org> References: <20220412062943.670770901@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: stable@vger.kernel.org From: NeilBrown [ Upstream commit a721035477fb5fb8abc738fbe410b07c12af3dc5 ] When memory is short, new worker threads cannot be created and we depend on the minimum one rpciod thread to be able to handle everything. So it must not block waiting for memory. xprt_dynamic_alloc_slot can block indefinitely. This can tie up all workqueue threads and NFS can deadlock. So when called from a workqueue, set __GFP_NORETRY. The rdma alloc_slot already does not block. However it sets the error to -EAGAIN suggesting this will trigger a sleep. It does not. As we can see in call_reserveresult(), only -ENOMEM causes a sleep. -EAGAIN causes immediate retry. Signed-off-by: NeilBrown Signed-off-by: Trond Myklebust Signed-off-by: Sasha Levin --- net/sunrpc/xprt.c | 5 ++++- net/sunrpc/xprtrdma/transport.c | 2 +- 2 files changed, 5 insertions(+), 2 deletions(-) diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c index 396a74974f60..75acde97d748 100644 --- a/net/sunrpc/xprt.c +++ b/net/sunrpc/xprt.c @@ -1690,12 +1690,15 @@ static bool xprt_throttle_congested(struct rpc_xprt *xprt, struct rpc_task *task static struct rpc_rqst *xprt_dynamic_alloc_slot(struct rpc_xprt *xprt) { struct rpc_rqst *req = ERR_PTR(-EAGAIN); + gfp_t gfp_mask = GFP_KERNEL; if (xprt->num_reqs >= xprt->max_reqs) goto out; ++xprt->num_reqs; spin_unlock(&xprt->reserve_lock); - req = kzalloc(sizeof(struct rpc_rqst), GFP_NOFS); + if (current->flags & PF_WQ_WORKER) + gfp_mask |= __GFP_NORETRY | __GFP_NOWARN; + req = kzalloc(sizeof(*req), gfp_mask); spin_lock(&xprt->reserve_lock); if (req != NULL) goto out; diff --git a/net/sunrpc/xprtrdma/transport.c b/net/sunrpc/xprtrdma/transport.c index 6268af7e0310..256b06a92391 100644 --- a/net/sunrpc/xprtrdma/transport.c +++ b/net/sunrpc/xprtrdma/transport.c @@ -525,7 +525,7 @@ xprt_rdma_alloc_slot(struct rpc_xprt *xprt, struct rpc_task *task) return; out_sleep: - task->tk_status = -EAGAIN; + task->tk_status = -ENOMEM; xprt_add_backlog(xprt, task); } -- 2.35.1