From patchwork Tue Nov 16 02:44:04 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: NeilBrown X-Patchwork-Id: 12621173 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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 18027C433EF for ; Tue, 16 Nov 2021 02:48:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F3B606320D for ; Tue, 16 Nov 2021 02:48:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1358054AbhKPCvd (ORCPT ); Mon, 15 Nov 2021 21:51:33 -0500 Received: from smtp-out1.suse.de ([195.135.220.28]:59388 "EHLO smtp-out1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242402AbhKPCtW (ORCPT ); Mon, 15 Nov 2021 21:49:22 -0500 Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 8CA8F212C9; Tue, 16 Nov 2021 02:46:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1637030773; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=f9JPZARu0omLin5bRQVSgWDU6wAXTb1AVpCm2PGq0QA=; b=atmetXEZDy8cMBJPuxGdsioA9iEEjKYPYqm8r3COaJLFACTYSEnML7mYQBMmGJy6qWq+sX 17efbj7aEBJcrchB+nb1mGhfUGNR07Lbzb50Y1OpJ6jJRTv1E1ym8QpibclWvHrVTz6UqJ 0VLAHKfisqbII2bdSfpPxKIVMbaS6ng= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1637030773; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=f9JPZARu0omLin5bRQVSgWDU6wAXTb1AVpCm2PGq0QA=; b=QhGRS68RrxSioGc5OYbdql4ol0fghFMX4at/b29RBqkbuBMOvukvloUoM4ifPSimpAdbic 4B6GESV1oZ1RaDBQ== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 3665113B70; Tue, 16 Nov 2021 02:46:10 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id 8gWHOXIbk2H0CAAAMHmgww (envelope-from ); Tue, 16 Nov 2021 02:46:10 +0000 Subject: [PATCH 06/13] SUNRPC/xprt: async tasks mustn't block waiting for memory From: NeilBrown To: Trond Myklebust , Anna Schumaker , Chuck Lever , Andrew Morton , Mel Gorman Cc: linux-nfs@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Date: Tue, 16 Nov 2021 13:44:04 +1100 Message-ID: <163703064454.25805.13286573055267156315.stgit@noble.brown> In-Reply-To: <163702956672.25805.16457749992977493579.stgit@noble.brown> References: <163702956672.25805.16457749992977493579.stgit@noble.brown> User-Agent: StGit/0.23 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org 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 --- 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 a02de2bddb28..47d207e416ab 100644 --- a/net/sunrpc/xprt.c +++ b/net/sunrpc/xprt.c @@ -1687,12 +1687,15 @@ 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_NOFS; 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(struct rpc_rqst), 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 a52277115500..32df23796747 100644 --- a/net/sunrpc/xprtrdma/transport.c +++ b/net/sunrpc/xprtrdma/transport.c @@ -521,7 +521,7 @@ 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); }