From patchwork Wed Dec 4 20:38:02 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Paulo Alcantara X-Patchwork-Id: 11273549 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 8752C138C for ; Wed, 4 Dec 2019 20:38:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5C1BE21823 for ; Wed, 4 Dec 2019 20:38:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=cjr.nz header.i=@cjr.nz header.b="e7NGvD4P" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728104AbfLDUic (ORCPT ); Wed, 4 Dec 2019 15:38:32 -0500 Received: from mx.cjr.nz ([51.158.111.142]:1820 "EHLO mx.cjr.nz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728053AbfLDUic (ORCPT ); Wed, 4 Dec 2019 15:38:32 -0500 Received: from authenticated-user (mx.cjr.nz [51.158.111.142]) (Authenticated sender: pc) by mx.cjr.nz (Postfix) with ESMTPSA id E1FB28132A; Wed, 4 Dec 2019 20:38:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cjr.nz; s=dkim; t=1575491909; h=from:from:reply-to:subject:subject: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=oShPpuq+ITPYDA5oK34v7g5z/ZzXy6EQV3uSSERETH8=; b=e7NGvD4PZiof/bWeTHWNeLn9O7MWFiB+OekfSF6TPwq9M7xU4M7qLPc7OT8gA8Mbe38QtJ NqaMjtnro3DhEUuwxpvh5pbFEEdxIlkcmNquriiGgvKk3bppyBlCEHna6R7sYCI2lVIe9B mKGSxVCpWEZ5vfl4ugynFdglMD10IfCyQMCeWJvPJoKxkuPFtzhaGq4OcziKOwxbq0qvwd +Wdc0XECKAja/g1c3oCt5NgCYxEN93VTcMqrwXNaxjNmg65z4J5UD0tifmEjphr9qOeWpC ZdMx4it5/dbtsgiwPcLZudl/FbYqgDymLGh1Vknos53bVk6wP3cmywCSpZF4kg== From: "Paulo Alcantara (SUSE)" To: smfrench@gmail.com Cc: linux-cifs@vger.kernel.org, "Paulo Alcantara (SUSE)" Subject: [PATCH v4 5/6] cifs: Fix potential deadlock when updating vol in cifs_reconnect() Date: Wed, 4 Dec 2019 17:38:02 -0300 Message-Id: <20191204203803.2316-6-pc@cjr.nz> In-Reply-To: <20191204203803.2316-1-pc@cjr.nz> References: <20191204203803.2316-1-pc@cjr.nz> MIME-Version: 1.0 Sender: linux-cifs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-cifs@vger.kernel.org We can't acquire volume lock while refreshing the DFS cache because cifs_reconnect() may call dfs_cache_update_vol() while we are walking through the volume list. To prevent that, make vol_info refcounted, create a temp list with all volumes eligible for refreshing, and then use it without any locks held. Besides, replace vol_lock with a spinlock and protect cache_ttl from concurrent accesses or changes. Signed-off-by: Paulo Alcantara (SUSE) --- fs/cifs/dfs_cache.c | 109 +++++++++++++++++++++++++++++++------------- 1 file changed, 77 insertions(+), 32 deletions(-) diff --git a/fs/cifs/dfs_cache.c b/fs/cifs/dfs_cache.c index 1d1f7c03931b..82c5d9a31f9e 100644 --- a/fs/cifs/dfs_cache.c +++ b/fs/cifs/dfs_cache.c @@ -49,15 +49,20 @@ struct cache_entry { struct vol_info { char *fullpath; + spinlock_t smb_vol_lock; struct smb_vol smb_vol; char *mntdata; struct list_head list; + struct list_head rlist; + struct kref refcnt; }; static struct kmem_cache *cache_slab __read_mostly; static struct workqueue_struct *dfscache_wq __read_mostly; static int cache_ttl; +static DEFINE_SPINLOCK(cache_ttl_lock); + static struct nls_table *cache_nlsc; /* @@ -69,7 +74,7 @@ static struct hlist_head cache_htable[CACHE_HTABLE_SIZE]; static DEFINE_MUTEX(list_lock); static LIST_HEAD(vol_list); -static DEFINE_MUTEX(vol_lock); +static DEFINE_SPINLOCK(vol_list_lock); static void refresh_cache_worker(struct work_struct *work); @@ -300,7 +305,6 @@ int dfs_cache_init(void) for (i = 0; i < CACHE_HTABLE_SIZE; i++) INIT_HLIST_HEAD(&cache_htable[i]); - cache_ttl = -1; cache_nlsc = load_nls_default(); cifs_dbg(FYI, "%s: initialized DFS referral cache\n", __func__); @@ -471,15 +475,15 @@ add_cache_entry(unsigned int hash, const char *path, hlist_add_head_rcu(&ce->hlist, &cache_htable[hash]); - mutex_lock(&vol_lock); - if (cache_ttl < 0) { + spin_lock(&cache_ttl_lock); + if (!cache_ttl) { cache_ttl = ce->ttl; queue_delayed_work(dfscache_wq, &refresh_task, cache_ttl * HZ); } else { cache_ttl = min_t(int, cache_ttl, ce->ttl); mod_delayed_work(dfscache_wq, &refresh_task, cache_ttl * HZ); } - mutex_unlock(&vol_lock); + spin_unlock(&cache_ttl_lock); return ce; } @@ -523,21 +527,32 @@ static inline void destroy_slab_cache(void) kmem_cache_destroy(cache_slab); } -static inline void free_vol(struct vol_info *vi) +static void __vol_release(struct vol_info *vi) { - list_del(&vi->list); kfree(vi->fullpath); kfree(vi->mntdata); cifs_cleanup_volume_info_contents(&vi->smb_vol); kfree(vi); } +static void vol_release(struct kref *kref) +{ + struct vol_info *vi = container_of(kref, struct vol_info, refcnt); + + spin_lock(&vol_list_lock); + list_del(&vi->list); + spin_unlock(&vol_list_lock); + __vol_release(vi); +} + static inline void free_vol_list(void) { struct vol_info *vi, *nvi; - list_for_each_entry_safe(vi, nvi, &vol_list, list) - free_vol(vi); + list_for_each_entry_safe(vi, nvi, &vol_list, list) { + list_del_init(&vi->list); + __vol_release(vi); + } } /** @@ -1156,10 +1171,13 @@ int dfs_cache_add_vol(char *mntdata, struct smb_vol *vol, const char *fullpath) goto err_free_fullpath; vi->mntdata = mntdata; + spin_lock_init(&vi->smb_vol_lock); + kref_init(&vi->refcnt); - mutex_lock(&vol_lock); + spin_lock(&vol_list_lock); list_add_tail(&vi->list, &vol_list); - mutex_unlock(&vol_lock); + spin_unlock(&vol_list_lock); + return 0; err_free_fullpath: @@ -1169,7 +1187,8 @@ int dfs_cache_add_vol(char *mntdata, struct smb_vol *vol, const char *fullpath) return rc; } -static inline struct vol_info *find_vol(const char *fullpath) +/* Must be called with vol_list_lock held */ +static struct vol_info *find_vol(const char *fullpath) { struct vol_info *vi; @@ -1191,7 +1210,6 @@ static inline struct vol_info *find_vol(const char *fullpath) */ int dfs_cache_update_vol(const char *fullpath, struct TCP_Server_Info *server) { - int rc; struct vol_info *vi; if (!fullpath || !server) @@ -1199,22 +1217,24 @@ int dfs_cache_update_vol(const char *fullpath, struct TCP_Server_Info *server) cifs_dbg(FYI, "%s: fullpath: %s\n", __func__, fullpath); - mutex_lock(&vol_lock); - + spin_lock(&vol_list_lock); vi = find_vol(fullpath); if (IS_ERR(vi)) { - rc = PTR_ERR(vi); - goto out; + spin_unlock(&vol_list_lock); + return PTR_ERR(vi); } + kref_get(&vi->refcnt); + spin_unlock(&vol_list_lock); cifs_dbg(FYI, "%s: updating volume info\n", __func__); + spin_lock(&vi->smb_vol_lock); memcpy(&vi->smb_vol.dstaddr, &server->dstaddr, sizeof(vi->smb_vol.dstaddr)); - rc = 0; + spin_unlock(&vi->smb_vol_lock); -out: - mutex_unlock(&vol_lock); - return rc; + kref_put(&vi->refcnt, vol_release); + + return 0; } /** @@ -1231,11 +1251,11 @@ void dfs_cache_del_vol(const char *fullpath) cifs_dbg(FYI, "%s: fullpath: %s\n", __func__, fullpath); - mutex_lock(&vol_lock); + spin_lock(&vol_list_lock); vi = find_vol(fullpath); - if (!IS_ERR(vi)) - free_vol(vi); - mutex_unlock(&vol_lock); + spin_unlock(&vol_list_lock); + + kref_put(&vi->refcnt, vol_release); } /* Get all tcons that are within a DFS namespace and can be refreshed */ @@ -1449,27 +1469,52 @@ static void refresh_tcon(struct vol_info *vi, struct cifs_tcon *tcon) */ static void refresh_cache_worker(struct work_struct *work) { - struct vol_info *vi; + struct vol_info *vi, *nvi; struct TCP_Server_Info *server; - LIST_HEAD(list); + LIST_HEAD(vols); + LIST_HEAD(tcons); struct cifs_tcon *tcon, *ntcon; - mutex_lock(&vol_lock); - + /* + * Find SMB volumes that are eligible (server->tcpStatus == CifsGood) + * for refreshing. + */ + spin_lock(&vol_list_lock); list_for_each_entry(vi, &vol_list, list) { server = get_tcp_server(&vi->smb_vol); if (!server) continue; - get_tcons(server, &list); - list_for_each_entry_safe(tcon, ntcon, &list, ulist) { + kref_get(&vi->refcnt); + list_add_tail(&vi->rlist, &vols); + put_tcp_server(server); + } + spin_unlock(&vol_list_lock); + + /* Walk through all TCONs and refresh any expired cache entry */ + list_for_each_entry_safe(vi, nvi, &vols, rlist) { + spin_lock(&vi->smb_vol_lock); + server = get_tcp_server(&vi->smb_vol); + spin_unlock(&vi->smb_vol_lock); + + if (!server) + goto next_vol; + + get_tcons(server, &tcons); + list_for_each_entry_safe(tcon, ntcon, &tcons, ulist) { refresh_tcon(vi, tcon); list_del_init(&tcon->ulist); cifs_put_tcon(tcon); } put_tcp_server(server); + +next_vol: + list_del_init(&vi->rlist); + kref_put(&vi->refcnt, vol_release); } + + spin_lock(&cache_ttl_lock); queue_delayed_work(dfscache_wq, &refresh_task, cache_ttl * HZ); - mutex_unlock(&vol_lock); + spin_unlock(&cache_ttl_lock); }