From patchwork Sun Mar 6 23:41:44 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: NeilBrown X-Patchwork-Id: 12770998 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 D567CC433F5 for ; Sun, 6 Mar 2022 23:42:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234456AbiCFXno (ORCPT ); Sun, 6 Mar 2022 18:43:44 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42226 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234455AbiCFXnn (ORCPT ); Sun, 6 Mar 2022 18:43:43 -0500 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 243E53C484 for ; Sun, 6 Mar 2022 15:42:50 -0800 (PST) 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-out2.suse.de (Postfix) with ESMTPS id D7B761F38E; Sun, 6 Mar 2022 23:42:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1646610168; 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=WEfcbq1/ee9eOf+W9MRAhDMLLa4E0bAnyxCt3gnhbfg=; b=lnQ1/++XaR21/kGuzD76VNliRPQaTxjFYf/75Kx7IDdVlXAUEgC4a68wvnLxNyhZXdn+o+ mpyfLDU4ew0VMTKJoy2X6uZTsuopTZVyjI4B6ucHFoS2R+U4JhBWgeW4xy3SNoS+ZZmMut sJ1DsVnOp3FK5um1LuVb/oShsK1hJb4= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1646610168; 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=WEfcbq1/ee9eOf+W9MRAhDMLLa4E0bAnyxCt3gnhbfg=; b=eZJCcONlhADOk+mgjSR2ycqQQ72QHL3h/muDiFqD+V2XiS0XM4O5ODXGmvCmwwURNuA5bO Exb1X2wFzRtQKpBA== 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 C8527134CD; Sun, 6 Mar 2022 23:42:47 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id gKCGIfdGJWIjWAAAMHmgww (envelope-from ); Sun, 06 Mar 2022 23:42:47 +0000 Subject: [PATCH 04/11] SUNRPC/xprt: async tasks mustn't block waiting for memory From: NeilBrown To: Trond Myklebust , Anna Schumaker Cc: linux-nfs@vger.kernel.org Date: Mon, 07 Mar 2022 10:41:44 +1100 Message-ID: <164661010495.31054.15493859799937151207.stgit@noble.brown> In-Reply-To: <164660993703.31054.17075972410545449555.stgit@noble.brown> References: <164660993703.31054.17075972410545449555.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..dbffb5147f16 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(*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 5714bf880e95..923e4b512ee9 100644 --- a/net/sunrpc/xprtrdma/transport.c +++ b/net/sunrpc/xprtrdma/transport.c @@ -517,7 +517,7 @@ 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); }