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 X-Spam-Level: X-Spam-Status: No, score=-2.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4604CC43142 for ; Thu, 21 Jun 2018 21:36:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 07DDB2243F for ; Thu, 21 Jun 2018 21:36:10 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 07DDB2243F Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=stgolabs.net Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933905AbeFUV3E (ORCPT ); Thu, 21 Jun 2018 17:29:04 -0400 Received: from smtp2.provo.novell.com ([137.65.250.81]:60559 "EHLO smtp2.provo.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933880AbeFUV3A (ORCPT ); Thu, 21 Jun 2018 17:29:00 -0400 Received: from linux-r8p5.suse.cz (prv-ext-foundry1int.gns.novell.com [137.65.251.240]) by smtp2.provo.novell.com with ESMTP (TLS encrypted); Thu, 21 Jun 2018 15:28:50 -0600 From: Davidlohr Bueso To: akpm@linux-foundation.org, torvalds@linux-foundation.org Cc: tgraf@suug.ch, herbert@gondor.apana.org.au, manfred@colorfullife.com, mhocko@kernel.org, guillaume.knispel@supersonicimagine.com, linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, dave@stgolabs.net, Davidlohr Bueso Subject: [PATCH 2/4] lib/rhashtable: guarantee initial hashtable allocation Date: Thu, 21 Jun 2018 14:28:23 -0700 Message-Id: <20180621212825.3059-3-dave@stgolabs.net> X-Mailer: git-send-email 2.16.4 In-Reply-To: <20180621212825.3059-1-dave@stgolabs.net> References: <20180621212825.3059-1-dave@stgolabs.net> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org rhashtable_init() may fail due to -ENOMEM, thus making the entire api unusable. This patch removes this scenario, however unlikely. In order to guarantee memory allocation, this patch always ends up doing GFP_KERNEL|__GFP_NOFAIL for both the tbl as well as alloc_bucket_spinlocks(). Upon the first table allocation failure, we shrink the size to the smallest value that makes sense and retry with __GFP_NOFAIL semantics. With the defaults, this means that from 64 buckets, we retry with only 4. Any later issues regarding performance due to collisions or larger table resizing (when more memory becomes available) is the least of our problems. Signed-off-by: Davidlohr Bueso --- lib/rhashtable.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/lib/rhashtable.c b/lib/rhashtable.c index 26c9cd8a985a..411c4041ce83 100644 --- a/lib/rhashtable.c +++ b/lib/rhashtable.c @@ -179,10 +179,11 @@ static struct bucket_table *bucket_table_alloc(struct rhashtable *ht, size = nbuckets; - if (tbl == NULL && gfp != GFP_KERNEL) { + if (tbl == NULL && (gfp & ~__GFP_NOFAIL) != GFP_KERNEL) { tbl = nested_bucket_table_alloc(ht, nbuckets, gfp); nbuckets = 0; } + if (tbl == NULL) return NULL; @@ -1065,9 +1066,16 @@ int rhashtable_init(struct rhashtable *ht, } } + /* + * This is api initialization and thus we need to guarantee the + * initial rhashtable allocation. Upon failure, retry with the + * smallest possible size with __GFP_NOFAIL semantics. + */ tbl = bucket_table_alloc(ht, size, GFP_KERNEL); - if (tbl == NULL) - return -ENOMEM; + if (unlikely(tbl == NULL)) { + size = max_t(u16, ht->p.min_size, HASH_MIN_SIZE); + tbl = bucket_table_alloc(ht, size, GFP_KERNEL | __GFP_NOFAIL); + } atomic_set(&ht->nelems, 0); -- 2.16.4