From patchwork Mon Nov 7 17:05:52 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Vlastimil Babka X-Patchwork-Id: 13034904 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 46D8DC4321E for ; Mon, 7 Nov 2022 17:06:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232559AbiKGRGC (ORCPT ); Mon, 7 Nov 2022 12:06:02 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54808 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232399AbiKGRGA (ORCPT ); Mon, 7 Nov 2022 12:06:00 -0500 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8322F1A20F; Mon, 7 Nov 2022 09:05:58 -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 70B181F383; Mon, 7 Nov 2022 17:05:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1667840757; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=oxt8DX9hjtQmJzjUJiAZ/pvWxZcY7FsbKiwy/1OaLtI=; b=1lzbk6FbmE1Ji+YX8AWT7ByzYWFkLM0klQ18smQktoXQgePMt4bnUreeY86am0yeokdgEB QtyUgF0y1bSbUbA4seztn2v1HaYPKT7kweuMv8/mtw7mvcTHFTpYuU3bI9UV1+pw3mhlYL zcc1aLbFLU9ErXpbWcHUaWMx8pOCWFM= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1667840757; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=oxt8DX9hjtQmJzjUJiAZ/pvWxZcY7FsbKiwy/1OaLtI=; b=FCrIbgvyydHhHw/n93XtEZbWSlxOoQ4AzWmAzv1mIMBmWnFUVUVo3fQQbiVVUehzRBXspC 3I84wT07/3zCFOBw== 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 45BDD13ADB; Mon, 7 Nov 2022 17:05:57 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id MNB2EPU6aWOYfwAAMHmgww (envelope-from ); Mon, 07 Nov 2022 17:05:57 +0000 From: Vlastimil Babka To: Christoph Lameter , David Rientjes , Joonsoo Kim , Pekka Enberg , Joel Fernandes Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>, Roman Gushchin , Matthew Wilcox , paulmck@kernel.org, rcu@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, patches@lists.linux.dev, Vlastimil Babka Subject: [PATCH v2 1/3] mm/slub: perform free consistency checks before call_rcu Date: Mon, 7 Nov 2022 18:05:52 +0100 Message-Id: <20221107170554.7869-2-vbabka@suse.cz> X-Mailer: git-send-email 2.38.0 In-Reply-To: <20221107170554.7869-1-vbabka@suse.cz> References: <20221107170554.7869-1-vbabka@suse.cz> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org For SLAB_TYPESAFE_BY_RCU caches we use call_rcu to perform empty slab freeing. The rcu callback rcu_free_slab() calls __free_slab() that currently includes checking the slab consistency for caches with SLAB_CONSISTENCY_CHECKS flags. This check needs the slab->objects field to be intact. Because in the next patch we want to allow rcu_head in struct slab to become larger in debug configurations and thus potentially overwrite more fields through a union than slab_list, we want to limit the fields used in rcu_free_slab(). Thus move the consistency checks to free_slab() before call_rcu(). This can be done safely even for SLAB_TYPESAFE_BY_RCU caches where accesses to the objects can still occur after freeing them. As a result, only the slab->slab_cache field has to be physically separate from rcu_head for the freeing callback to work. We also save some cycles in the rcu callback for caches with consistency checks enabled. Signed-off-by: Vlastimil Babka Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com> --- mm/slub.c | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-) diff --git a/mm/slub.c b/mm/slub.c index 157527d7101b..99ba865afc4a 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -1999,14 +1999,6 @@ static void __free_slab(struct kmem_cache *s, struct slab *slab) int order = folio_order(folio); int pages = 1 << order; - if (kmem_cache_debug_flags(s, SLAB_CONSISTENCY_CHECKS)) { - void *p; - - slab_pad_check(s, slab); - for_each_object(p, s, slab_address(slab), slab->objects) - check_object(s, slab, p, SLUB_RED_INACTIVE); - } - __slab_clear_pfmemalloc(slab); __folio_clear_slab(folio); folio->mapping = NULL; @@ -2025,9 +2017,17 @@ static void rcu_free_slab(struct rcu_head *h) static void free_slab(struct kmem_cache *s, struct slab *slab) { - if (unlikely(s->flags & SLAB_TYPESAFE_BY_RCU)) { + if (kmem_cache_debug_flags(s, SLAB_CONSISTENCY_CHECKS)) { + void *p; + + slab_pad_check(s, slab); + for_each_object(p, s, slab_address(slab), slab->objects) + check_object(s, slab, p, SLUB_RED_INACTIVE); + } + + if (unlikely(s->flags & SLAB_TYPESAFE_BY_RCU)) call_rcu(&slab->rcu_head, rcu_free_slab); - } else + else __free_slab(s, slab); }