From patchwork Thu Dec 16 23:48:23 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: NeilBrown X-Patchwork-Id: 12683113 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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id C827CC433F5 for ; Thu, 16 Dec 2021 23:58:24 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 5994D6B0083; Thu, 16 Dec 2021 18:53:50 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 522B76B0085; Thu, 16 Dec 2021 18:53:50 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 39CDB6B0087; Thu, 16 Dec 2021 18:53:50 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0111.hostedemail.com [216.40.44.111]) by kanga.kvack.org (Postfix) with ESMTP id 28F556B0083 for ; Thu, 16 Dec 2021 18:53:50 -0500 (EST) Received: from smtpin03.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id E3FE4181AC9CC for ; Thu, 16 Dec 2021 23:53:39 +0000 (UTC) X-FDA: 78925312158.03.1B645AC Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by imf03.hostedemail.com (Postfix) with ESMTP id 6C9C72000F for ; Thu, 16 Dec 2021 23:53:39 +0000 (UTC) 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 4D7EA212C8; Thu, 16 Dec 2021 23:53:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1639698818; 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=uJLgBSr+4ac2HtnFPf6KLC0wSgPyRK3wpQcub+LxsjE=; b=B5BZGrGhS1sLx+jn04Rr1MuE1ChyurPGtdI+nwDT/Hr/0+QXFKuZRtGCvuCRNoIkwlwyKP 9BfV/qhMuMbcQqDMBat4fq1Wo0xQWckKo0jCjlYNMmPl0tfn2JBp9hUPp/dnjydtCifmiB 8RRyHATryW0Fh+YgaDAS7VV2qTL3pAI= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1639698818; 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=uJLgBSr+4ac2HtnFPf6KLC0wSgPyRK3wpQcub+LxsjE=; b=+QQyfMGX2CvZGYolzHHLcWwYdfeq3Mk7+x940MXnO+mysULhS3FXrt8AFWVVKGMrMf+WAT O4p/XR+Idp/HN7CA== 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 564E413EFD; Thu, 16 Dec 2021 23:53:35 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id qkUhBX/Ru2GpWwAAMHmgww (envelope-from ); Thu, 16 Dec 2021 23:53:35 +0000 Subject: [PATCH 11/18] SUNRPC/call_alloc: async tasks mustn't block waiting for memory From: NeilBrown To: Trond Myklebust , Anna Schumaker , Chuck Lever , Andrew Morton , Mel Gorman , Christoph Hellwig , David Howells Cc: linux-nfs@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Date: Fri, 17 Dec 2021 10:48:23 +1100 Message-ID: <163969850317.20885.3872948365489724355.stgit@noble.brown> In-Reply-To: <163969801519.20885.3977673503103544412.stgit@noble.brown> References: <163969801519.20885.3977673503103544412.stgit@noble.brown> User-Agent: StGit/0.23 MIME-Version: 1.0 Authentication-Results: imf03.hostedemail.com; dkim=pass header.d=suse.de header.s=susede2_rsa header.b=B5BZGrGh; dkim=pass header.d=suse.de header.s=susede2_ed25519 header.b=+QQyfMGX; spf=pass (imf03.hostedemail.com: domain of neilb@suse.de designates 195.135.220.28 as permitted sender) smtp.mailfrom=neilb@suse.de; dmarc=pass (policy=none) header.from=suse.de X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 6C9C72000F X-Stat-Signature: 4u653njguka7dsggs6ocecend9nrc1ie X-HE-Tag: 1639698819-716789 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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. mempools are particularly a problem as memory can only be released back to the mempool by an async rpc task running. If all available workqueue threads are waiting on the mempool, no thread is available to return anything. rpc_malloc() can block, and this might cause deadlocks. So check RPC_IS_ASYNC(), rather than RPC_IS_SWAPPER() to determine if blocking is acceptable. Signed-off-by: NeilBrown --- net/sunrpc/sched.c | 4 +++- net/sunrpc/xprtrdma/transport.c | 4 +++- 2 files changed, 6 insertions(+), 2 deletions(-) diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c index e2c835482791..d5b6e897f5a5 100644 --- a/net/sunrpc/sched.c +++ b/net/sunrpc/sched.c @@ -1023,8 +1023,10 @@ int rpc_malloc(struct rpc_task *task) struct rpc_buffer *buf; gfp_t gfp = GFP_NOFS; + if (RPC_IS_ASYNC(task)) + gfp = GFP_NOWAIT | __GFP_NOWARN; if (RPC_IS_SWAPPER(task)) - gfp = __GFP_MEMALLOC | GFP_NOWAIT | __GFP_NOWARN; + gfp |= __GFP_MEMALLOC; size += sizeof(struct rpc_buffer); if (size <= RPC_BUFFER_MAXSIZE) diff --git a/net/sunrpc/xprtrdma/transport.c b/net/sunrpc/xprtrdma/transport.c index 16e5696314a4..a52277115500 100644 --- a/net/sunrpc/xprtrdma/transport.c +++ b/net/sunrpc/xprtrdma/transport.c @@ -574,8 +574,10 @@ xprt_rdma_allocate(struct rpc_task *task) gfp_t flags; flags = RPCRDMA_DEF_GFP; + if (RPC_IS_ASYNC(task)) + flags = GFP_NOWAIT | __GFP_NOWARN; if (RPC_IS_SWAPPER(task)) - flags = __GFP_MEMALLOC | GFP_NOWAIT | __GFP_NOWARN; + flags |= __GFP_MEMALLOC; if (!rpcrdma_check_regbuf(r_xprt, req->rl_sendbuf, rqst->rq_callsize, flags))