From patchwork Fri Mar 17 10:43:07 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Vlastimil Babka X-Patchwork-Id: 13178874 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 DFEEBC7618B for ; Fri, 17 Mar 2023 10:45:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229784AbjCQKpA (ORCPT ); Fri, 17 Mar 2023 06:45:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37018 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230401AbjCQKo0 (ORCPT ); Fri, 17 Mar 2023 06:44:26 -0400 Received: from smtp-out2.suse.de (smtp-out2.suse.de [IPv6:2001:67c:2178:6::1d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0A2832D70; Fri, 17 Mar 2023 03:43:52 -0700 (PDT) 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 6441E1FE12; Fri, 17 Mar 2023 10:43:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1679049804; 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=QMYqXFz2IaKT3NUuszy4Agqdpp++dYT+bm01yseqepo=; b=3RpsWYEBsUt1LFWxCtGa654D5WiAY6xlDzmguCq7ZIYVl2lubbeAt4r2RFSsxW0nlHA/eC c3wX6HGC3gUendkoyOfqOmUfJnYC2pOdF4XUXI+knSdJQj7iD7m2tiRkWNW32AwwO/Wf7W +qXw0+FixUwDXTRG+OSphmXADh28IKA= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1679049804; 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=QMYqXFz2IaKT3NUuszy4Agqdpp++dYT+bm01yseqepo=; b=L+rlwaT8LS9vjdsg9XHVyHNS5hCWePW/zbB/fIp1ejwCCCjFDK4vtitN8q9Zka3g3gxPfG K86/MFNPW7+ZsxAQ== 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 CF23E1346F; Fri, 17 Mar 2023 10:43:23 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id yMbfMUtEFGRgdwAAMHmgww (envelope-from ); Fri, 17 Mar 2023 10:43:23 +0000 From: Vlastimil Babka To: Christoph Lameter , David Rientjes , Joonsoo Kim , Pekka Enberg Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>, Roman Gushchin , Andrew Morton , linux-mm@kvack.org, rcu@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, patches@lists.linux.dev, linux-doc@vger.kernel.org, Vlastimil Babka , Mike Rapoport , Jonathan Corbet , "Paul E. McKenney" , Frederic Weisbecker , Neeraj Upadhyay , Josh Triplett , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , Joel Fernandes Subject: [PATCH v2 6/6] mm/slab: document kfree() as allowed for kmem_cache_alloc() objects Date: Fri, 17 Mar 2023 11:43:07 +0100 Message-Id: <20230317104307.29328-7-vbabka@suse.cz> X-Mailer: git-send-email 2.40.0 In-Reply-To: <20230317104307.29328-1-vbabka@suse.cz> References: <20230317104307.29328-1-vbabka@suse.cz> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org This will make it easier to free objects in situations when they can come from either kmalloc() or kmem_cache_alloc(), and also allow kfree_rcu() for freeing objects from kmem_cache_alloc(). For the SLAB and SLUB allocators this was always possible so with SLOB gone, we can document it as supported. Signed-off-by: Vlastimil Babka Cc: Mike Rapoport Cc: Jonathan Corbet Cc: "Paul E. McKenney" Cc: Frederic Weisbecker Cc: Neeraj Upadhyay Cc: Josh Triplett Cc: Steven Rostedt Cc: Mathieu Desnoyers Cc: Lai Jiangshan Cc: Joel Fernandes Reviewed-by: Mike Rapoport (IBM) --- Documentation/core-api/memory-allocation.rst | 17 +++++++++++++---- include/linux/rcupdate.h | 6 ++++-- mm/slab_common.c | 5 +---- 3 files changed, 18 insertions(+), 10 deletions(-) diff --git a/Documentation/core-api/memory-allocation.rst b/Documentation/core-api/memory-allocation.rst index 5954ddf6ee13..1c58d883b273 100644 --- a/Documentation/core-api/memory-allocation.rst +++ b/Documentation/core-api/memory-allocation.rst @@ -170,7 +170,16 @@ should be used if a part of the cache might be copied to the userspace. After the cache is created kmem_cache_alloc() and its convenience wrappers can allocate memory from that cache. -When the allocated memory is no longer needed it must be freed. You can -use kvfree() for the memory allocated with `kmalloc`, `vmalloc` and -`kvmalloc`. The slab caches should be freed with kmem_cache_free(). And -don't forget to destroy the cache with kmem_cache_destroy(). +When the allocated memory is no longer needed it must be freed. + +Objects allocated by `kmalloc` can be freed by `kfree` or `kvfree`. Objects +allocated by `kmem_cache_alloc` can be freed with `kmem_cache_free`, `kfree` +or `kvfree`, where the latter two might be more convenient thanks to not +needing the kmem_cache pointer. + +The same rules apply to _bulk and _rcu flavors of freeing functions. + +Memory allocated by `vmalloc` can be freed with `vfree` or `kvfree`. +Memory allocated by `kvmalloc` can be freed with `kvfree`. +Caches created by `kmem_cache_create` should be freed with +`kmem_cache_destroy` only after freeing all the allocated objects first. diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 094321c17e48..dcd2cf1e8326 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -976,8 +976,10 @@ static inline notrace void rcu_read_unlock_sched_notrace(void) * either fall back to use of call_rcu() or rearrange the structure to * position the rcu_head structure into the first 4096 bytes. * - * Note that the allowable offset might decrease in the future, for example, - * to allow something like kmem_cache_free_rcu(). + * The object to be freed can be allocated either by kmalloc() or + * kmem_cache_alloc(). + * + * Note that the allowable offset might decrease in the future. * * The BUILD_BUG_ON check must not involve any function calls, hence the * checks are done in macros here. diff --git a/mm/slab_common.c b/mm/slab_common.c index 1522693295f5..607249785c07 100644 --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -989,12 +989,9 @@ EXPORT_SYMBOL(__kmalloc_node_track_caller); /** * kfree - free previously allocated memory - * @object: pointer returned by kmalloc. + * @object: pointer returned by kmalloc() or kmem_cache_alloc() * * If @object is NULL, no operation is performed. - * - * Don't free memory not originally allocated by kmalloc() - * or you will run into trouble. */ void kfree(const void *object) {