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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 665CAC433F5 for ; Thu, 10 Mar 2022 18:27:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245447AbiCJS25 (ORCPT ); Thu, 10 Mar 2022 13:28:57 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42068 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242094AbiCJS2y (ORCPT ); Thu, 10 Mar 2022 13:28:54 -0500 Received: from out30-130.freemail.mail.aliyun.com (out30-130.freemail.mail.aliyun.com [115.124.30.130]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 577C9A7754 for ; Thu, 10 Mar 2022 10:27:52 -0800 (PST) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R201e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04394;MF=hsiangkao@linux.alibaba.com;NM=1;PH=DS;RN=4;SR=0;TI=SMTPD_---0V6pgl69_1646936864; Received: from e18g06460.et15sqa.tbsite.net(mailfrom:hsiangkao@linux.alibaba.com fp:SMTPD_---0V6pgl69_1646936864) by smtp.aliyun-inc.com(127.0.0.1); Fri, 11 Mar 2022 02:27:50 +0800 From: Gao Xiang To: linux-erofs@lists.ozlabs.org, Chao Yu Cc: LKML , Gao Xiang Subject: [PATCH 1/2] erofs: clean up z_erofs_extent_lookback Date: Fri, 11 Mar 2022 02:27:42 +0800 Message-Id: <20220310182743.102365-1-hsiangkao@linux.alibaba.com> X-Mailer: git-send-email 2.24.4 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Avoid the unnecessary tail recursion since it can be converted into a loop directly in order to prevent potential stack overflow. It's a pretty straightforward conversion. Signed-off-by: Gao Xiang --- fs/erofs/zmap.c | 67 ++++++++++++++++++++++++------------------------- 1 file changed, 33 insertions(+), 34 deletions(-) diff --git a/fs/erofs/zmap.c b/fs/erofs/zmap.c index b4059b9c3bac..572f0b8151ba 100644 --- a/fs/erofs/zmap.c +++ b/fs/erofs/zmap.c @@ -431,48 +431,47 @@ static int z_erofs_extent_lookback(struct z_erofs_maprecorder *m, unsigned int lookback_distance) { struct erofs_inode *const vi = EROFS_I(m->inode); - struct erofs_map_blocks *const map = m->map; const unsigned int lclusterbits = vi->z_logical_clusterbits; - unsigned long lcn = m->lcn; - int err; - if (lcn < lookback_distance) { - erofs_err(m->inode->i_sb, - "bogus lookback distance @ nid %llu", vi->nid); - DBG_BUGON(1); - return -EFSCORRUPTED; - } + while (m->lcn >= lookback_distance) { + unsigned long lcn = m->lcn - lookback_distance; + int err; - /* load extent head logical cluster if needed */ - lcn -= lookback_distance; - err = z_erofs_load_cluster_from_disk(m, lcn, false); - if (err) - return err; + /* load extent head logical cluster if needed */ + err = z_erofs_load_cluster_from_disk(m, lcn, false); + if (err) + return err; - switch (m->type) { - case Z_EROFS_VLE_CLUSTER_TYPE_NONHEAD: - if (!m->delta[0]) { + switch (m->type) { + case Z_EROFS_VLE_CLUSTER_TYPE_NONHEAD: + if (!m->delta[0]) { + erofs_err(m->inode->i_sb, + "invalid lookback distance 0 @ nid %llu", + vi->nid); + DBG_BUGON(1); + return -EFSCORRUPTED; + } + lookback_distance = m->delta[0]; + continue; + case Z_EROFS_VLE_CLUSTER_TYPE_PLAIN: + case Z_EROFS_VLE_CLUSTER_TYPE_HEAD1: + case Z_EROFS_VLE_CLUSTER_TYPE_HEAD2: + m->headtype = m->type; + m->map->m_la = (lcn << lclusterbits) | m->clusterofs; + return 0; + default: erofs_err(m->inode->i_sb, - "invalid lookback distance 0 @ nid %llu", - vi->nid); + "unknown type %u @ lcn %lu of nid %llu", + m->type, lcn, vi->nid); DBG_BUGON(1); - return -EFSCORRUPTED; + return -EOPNOTSUPP; } - return z_erofs_extent_lookback(m, m->delta[0]); - case Z_EROFS_VLE_CLUSTER_TYPE_PLAIN: - case Z_EROFS_VLE_CLUSTER_TYPE_HEAD1: - case Z_EROFS_VLE_CLUSTER_TYPE_HEAD2: - m->headtype = m->type; - map->m_la = (lcn << lclusterbits) | m->clusterofs; - break; - default: - erofs_err(m->inode->i_sb, - "unknown type %u @ lcn %lu of nid %llu", - m->type, lcn, vi->nid); - DBG_BUGON(1); - return -EOPNOTSUPP; } - return 0; + + erofs_err(m->inode->i_sb, "bogus lookback distance @ nid %llu", + vi->nid); + DBG_BUGON(1); + return -EFSCORRUPTED; } static int z_erofs_get_extent_compressedlen(struct z_erofs_maprecorder *m, -- 2.24.4