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: 12683115 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 F2783C433EF for ; Thu, 16 Dec 2021 23:58:57 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 2657F6B0085; Thu, 16 Dec 2021 18:53:57 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 1EED76B0087; Thu, 16 Dec 2021 18:53:57 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0696C6B0088; Thu, 16 Dec 2021 18:53:57 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0216.hostedemail.com [216.40.44.216]) by kanga.kvack.org (Postfix) with ESMTP id E97496B0085 for ; Thu, 16 Dec 2021 18:53:56 -0500 (EST) Received: from smtpin10.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id A9C5C8632A for ; Thu, 16 Dec 2021 23:53:46 +0000 (UTC) X-FDA: 78925312452.10.F36239B Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by imf30.hostedemail.com (Postfix) with ESMTP id 15C0080011 for ; Thu, 16 Dec 2021 23:53:45 +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 21B742111A; Thu, 16 Dec 2021 23:53:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1639698825; 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=/Xf0wQNVm3xiMoEph9xuiX0w4MC4SZqJ4flfzelN2po=; b=HvkZQeCMFZCPSVQFUK/PUY7B7v+NLZpUF/m3Yj4xJKsbEa2leGoz9gqvwpHJBag+WefWI6 0VBcdl08xnIcY9vXn22pP/IeYzRGO28wyAsDZqf87G24s8KrbkeUDwXMNDYgmtPjvbHcDh qpdO8NC1Q9cEMZN1/U1R1NMXfhuVzC0= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1639698825; 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=/Xf0wQNVm3xiMoEph9xuiX0w4MC4SZqJ4flfzelN2po=; b=vZy0FnDUXHJwQKOG4m/0/p1GY8oOwPXQ5ScsZz3bmlnHvp6t/QmB/UuBmIoCdt7YEvO6Gw uqEETfQGhz4AvEAg== 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 2C84913EFD; Thu, 16 Dec 2021 23:53:41 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id RrWdNoXRu2GtWwAAMHmgww (envelope-from ); Thu, 16 Dec 2021 23:53:41 +0000 Subject: [PATCH 12/18] SUNRPC/auth: 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: <163969850320.20885.16756746953092069326.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: imf30.hostedemail.com; dkim=pass header.d=suse.de header.s=susede2_rsa header.b=HvkZQeCM; dkim=pass header.d=suse.de header.s=susede2_ed25519 header.b=vZy0FnDU; spf=pass (imf30.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-Queue-Id: 15C0080011 X-Stat-Signature: weu1upywazetanqz5pkeartdju7spi9m X-Rspamd-Server: rspam04 X-HE-Tag: 1639698825-765768 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. lookup_cred() can block on a mempool or kmalloc - and this can cause deadlocks. So add a new RPCAUTH_LOOKUP flag for async lookups and don't block on memory. If the -ENOMEM gets back to call_refreshresult(), wait a short while and try again. HZ>>4 is chosen as it is used elsewhere for -ENOMEM retries. Signed-off-by: NeilBrown --- include/linux/sunrpc/auth.h | 1 + net/sunrpc/auth.c | 6 +++++- net/sunrpc/auth_gss/auth_gss.c | 6 +++++- net/sunrpc/auth_unix.c | 10 ++++++++-- net/sunrpc/clnt.c | 3 +++ 5 files changed, 22 insertions(+), 4 deletions(-) diff --git a/include/linux/sunrpc/auth.h b/include/linux/sunrpc/auth.h index 98da816b5fc2..3e6ce288a7fc 100644 --- a/include/linux/sunrpc/auth.h +++ b/include/linux/sunrpc/auth.h @@ -99,6 +99,7 @@ struct rpc_auth_create_args { /* Flags for rpcauth_lookupcred() */ #define RPCAUTH_LOOKUP_NEW 0x01 /* Accept an uninitialised cred */ +#define RPCAUTH_LOOKUP_ASYNC 0x02 /* Don't block waiting for memory */ /* * Client authentication ops diff --git a/net/sunrpc/auth.c b/net/sunrpc/auth.c index a9f0d17fdb0d..6bfa19f9fa6a 100644 --- a/net/sunrpc/auth.c +++ b/net/sunrpc/auth.c @@ -615,6 +615,8 @@ rpcauth_bind_root_cred(struct rpc_task *task, int lookupflags) }; struct rpc_cred *ret; + if (RPC_IS_ASYNC(task)) + lookupflags |= RPCAUTH_LOOKUP_ASYNC; ret = auth->au_ops->lookup_cred(auth, &acred, lookupflags); put_cred(acred.cred); return ret; @@ -631,6 +633,8 @@ rpcauth_bind_machine_cred(struct rpc_task *task, int lookupflags) if (!acred.principal) return NULL; + if (RPC_IS_ASYNC(task)) + lookupflags |= RPCAUTH_LOOKUP_ASYNC; return auth->au_ops->lookup_cred(auth, &acred, lookupflags); } @@ -654,7 +658,7 @@ rpcauth_bindcred(struct rpc_task *task, const struct cred *cred, int flags) }; if (flags & RPC_TASK_ASYNC) - lookupflags |= RPCAUTH_LOOKUP_NEW; + lookupflags |= RPCAUTH_LOOKUP_NEW | RPCAUTH_LOOKUP_ASYNC; if (task->tk_op_cred) /* Task must use exactly this rpc_cred */ new = get_rpccred(task->tk_op_cred); diff --git a/net/sunrpc/auth_gss/auth_gss.c b/net/sunrpc/auth_gss/auth_gss.c index 5f42aa5fc612..df72d6301f78 100644 --- a/net/sunrpc/auth_gss/auth_gss.c +++ b/net/sunrpc/auth_gss/auth_gss.c @@ -1341,7 +1341,11 @@ gss_hash_cred(struct auth_cred *acred, unsigned int hashbits) static struct rpc_cred * gss_lookup_cred(struct rpc_auth *auth, struct auth_cred *acred, int flags) { - return rpcauth_lookup_credcache(auth, acred, flags, GFP_NOFS); + gfp_t gfp = GFP_NOFS; + + if (flags & RPCAUTH_LOOKUP_ASYNC) + gfp = GFP_NOWAIT | __GFP_NOWARN; + return rpcauth_lookup_credcache(auth, acred, flags, gfp); } static struct rpc_cred * diff --git a/net/sunrpc/auth_unix.c b/net/sunrpc/auth_unix.c index e7df1f782b2e..e5819265dd1b 100644 --- a/net/sunrpc/auth_unix.c +++ b/net/sunrpc/auth_unix.c @@ -43,8 +43,14 @@ unx_destroy(struct rpc_auth *auth) static struct rpc_cred * unx_lookup_cred(struct rpc_auth *auth, struct auth_cred *acred, int flags) { - struct rpc_cred *ret = mempool_alloc(unix_pool, GFP_NOFS); - + gfp_t gfp = GFP_NOFS; + struct rpc_cred *ret; + + if (flags & RPCAUTH_LOOKUP_ASYNC) + gfp = GFP_NOWAIT | __GFP_NOWARN; + ret = mempool_alloc(unix_pool, gfp); + if (!ret) + return ERR_PTR(-ENOMEM); rpcauth_init_cred(ret, acred, auth, &unix_credops); ret->cr_flags = 1UL << RPCAUTH_CRED_UPTODATE; return ret; diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c index a312ea2bc440..238b2ef5491f 100644 --- a/net/sunrpc/clnt.c +++ b/net/sunrpc/clnt.c @@ -1745,6 +1745,9 @@ call_refreshresult(struct rpc_task *task) task->tk_cred_retry--; trace_rpc_retry_refresh_status(task); return; + case -ENOMEM: + rpc_delay(task, HZ >> 4); + return; } trace_rpc_refresh_status(task); rpc_call_rpcerror(task, status);