From patchwork Thu Apr 12 11:50:52 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Coly Li X-Patchwork-Id: 10338429 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 62EAE604D4 for ; Thu, 12 Apr 2018 11:51:06 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 54529287FF for ; Thu, 12 Apr 2018 11:51:06 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 48B9C28806; Thu, 12 Apr 2018 11:51:06 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00, MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id B078C287FF for ; Thu, 12 Apr 2018 11:51:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751863AbeDLLvE (ORCPT ); Thu, 12 Apr 2018 07:51:04 -0400 Received: from mx2.suse.de ([195.135.220.15]:49287 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751112AbeDLLvE (ORCPT ); Thu, 12 Apr 2018 07:51:04 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (charybdis-ext.suse.de [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id BA9E5AC81; Thu, 12 Apr 2018 11:51:02 +0000 (UTC) From: Coly Li To: linux-bcache@vger.kernel.org Cc: linux-block@vger.kernel.org, Coly Li Subject: [PATCH 1/2] bcache: remove unncessary code in bch_btree_keys_init() Date: Thu, 12 Apr 2018 19:50:52 +0800 Message-Id: <20180412115053.125321-1-colyli@suse.de> X-Mailer: git-send-email 2.16.2 Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Function bch_btree_keys_init() initializes b->set[].size and b->set[].data to zero. As the code comments indicates, these code indeed is unncessary, because both struct btree_keys and struct bset_tree are nested embedded into struct btree, when struct btree is filled with 0 bits by kzalloc() in mca_bucket_alloc(), b->set[].size and b->set[].data are initialized to 0 (a.k.a NULL) already. This patch removes the redundant code, and add comments in bch_btree_keys_init() and mca_bucket_alloc() to explain why it's safe. Signed-off-by: Coly Li --- drivers/md/bcache/bset.c | 13 ++++++------- drivers/md/bcache/btree.c | 4 ++++ 2 files changed, 10 insertions(+), 7 deletions(-) diff --git a/drivers/md/bcache/bset.c b/drivers/md/bcache/bset.c index 579c696a5fe0..343f4e9428e0 100644 --- a/drivers/md/bcache/bset.c +++ b/drivers/md/bcache/bset.c @@ -352,15 +352,14 @@ void bch_btree_keys_init(struct btree_keys *b, const struct btree_keys_ops *ops, b->nsets = 0; b->last_set_unwritten = 0; - /* XXX: shouldn't be needed */ - for (i = 0; i < MAX_BSETS; i++) - b->set[i].size = 0; /* - * Second loop starts at 1 because b->keys[0]->data is the memory we - * allocated + * struct btree_keys in embedded in struct btree, and struct + * bset_tree is embedded into struct btree_keys. They are all + * initialized as 0 by kzalloc() in mca_bucket_alloc(), and + * b->set[0].data is allocated in bch_btree_keys_alloc(), so we + * don't have to initiate b->set[].size and b->set[].data here + * any more. */ - for (i = 1; i < MAX_BSETS; i++) - b->set[i].data = NULL; } EXPORT_SYMBOL(bch_btree_keys_init); diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c index 17936b2dc7d6..344641e23415 100644 --- a/drivers/md/bcache/btree.c +++ b/drivers/md/bcache/btree.c @@ -600,6 +600,10 @@ static void mca_data_alloc(struct btree *b, struct bkey *k, gfp_t gfp) static struct btree *mca_bucket_alloc(struct cache_set *c, struct bkey *k, gfp_t gfp) { + /* + * kzalloc() is necessary here for initialization, + * see code comments in bch_btree_keys_init(). + */ struct btree *b = kzalloc(sizeof(struct btree), gfp); if (!b) return NULL;