From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933497AbeE1Ju2 (ORCPT ); Mon, 28 May 2018 05:50:28 -0400 Received: from orcrist.hmeau.com ([104.223.48.154]:40950 "EHLO deadmen.hmeau.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932300AbeE1JuG (ORCPT ); Mon, 28 May 2018 05:50:06 -0400 Date: Mon, 28 May 2018 17:49:56 +0800 From: Herbert Xu To: Davidlohr Bueso Cc: akpm@linux-foundation.org, torvalds@linux-foundation.org, tgraf@suug.ch, manfred@colorfullife.com, guillaume.knispel@supersonicimagine.com, linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, Davidlohr Bueso Subject: Re: [PATCH 2/6] lib/rhashtable: guarantee initial hashtable allocation Message-ID: <20180528094956.zaxusqqju3wtbdcz@gondor.apana.org.au> References: <20180524211135.27760-1-dave@stgolabs.net> <20180524211135.27760-3-dave@stgolabs.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180524211135.27760-3-dave@stgolabs.net> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 24, 2018 at 02:11:31PM -0700, Davidlohr Bueso wrote: > > -static struct bucket_table *bucket_table_alloc(struct rhashtable *ht, > - size_t nbuckets, > - gfp_t gfp) > +static struct bucket_table *__bucket_table_alloc(struct rhashtable *ht, > + size_t nbuckets, > + gfp_t gfp, bool retry) > { > struct bucket_table *tbl = NULL; > size_t size, max_locks; > int i; > > size = sizeof(*tbl) + nbuckets * sizeof(tbl->buckets[0]); > + if (retry) { > + gfp |= __GFP_NOFAIL; > + tbl = kzalloc(size, gfp); > + } /* fall-through */ I'd prefer this logic to be moved to the caller. So just call the function with GFP_KERNEL | __GFP_NOFAIL. Of course you need to modify bucket_table_alloc so that it still treats this as GFP_KERNEL (as opposed to GFP_ATOMIC). That is, instead of > if (gfp != GFP_KERNEL) You will need if ((gfp & ~__GFP_NOFAIL) != GFP_KERNEL) > @@ -1067,9 +1086,20 @@ int rhashtable_init(struct rhashtable *ht, > } > } > > + /* > + * This is api initialization and thus we need to guarantee the > + * initial rhashtable allocation. Upon failure, retry with a > + * smallest possible size, otherwise we exhaust our options with > + * __GFP_NOFAIL. > + */ > tbl = bucket_table_alloc(ht, size, GFP_KERNEL); > - if (tbl == NULL) > - return -ENOMEM; > + if (unlikely(tbl == NULL)) { > + size = HASH_MIN_SIZE; > + > + tbl = bucket_table_alloc(ht, size, GFP_KERNEL); > + if (tbl == NULL) > + tbl = bucket_table_alloc_retry(ht, size, GFP_KERNEL); > + } Perhaps you should also explain here why we don't just try the minimum size with __GFP_NOFAIL as the second step rather than the third. Cheers, -- Email: Herbert Xu Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt