From patchwork Wed Nov 27 00:36:31 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Paulo Alcantara X-Patchwork-Id: 11263181 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 21EF513A4 for ; Wed, 27 Nov 2019 00:37:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EC7EA2075C for ; Wed, 27 Nov 2019 00:37:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=cjr.nz header.i=@cjr.nz header.b="ocfJqy/s" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726947AbfK0Ah1 (ORCPT ); Tue, 26 Nov 2019 19:37:27 -0500 Received: from mx.cjr.nz ([51.158.111.142]:16170 "EHLO mx.cjr.nz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726987AbfK0Ah1 (ORCPT ); Tue, 26 Nov 2019 19:37:27 -0500 Received: from authenticated-user (mx.cjr.nz [51.158.111.142]) (Authenticated sender: pc) by mx.cjr.nz (Postfix) with ESMTPSA id 1A6BD80A26; Wed, 27 Nov 2019 00:37:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cjr.nz; s=dkim; t=1574815044; 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=DpHBhEnUUIoahJEhGFgZPlfRMhNslA67yh56V3D8Qbk=; b=ocfJqy/sX8XfyOzmUB50qqgrkl/nG8Dl5PkIK52vPzRsNcGQIhhb42yYcKPbW1n+RtC7x4 7QZfVL5Ms6YLsu4cGsYS2zZHIo/RCW35MLd6MSl/1o+QW8n5UVs0S5oKzBX7IlEjqTCQWt uTiNpY3MlM0uVBqXpbQXLW9HcJaJpJOyauKalXVZi0GQCt/qBwqiMYgwrcvMxcq1Z2+nbq KLSkyE2a3OI3z9IQtOlPLTHD8LAzRHxZWVA4jAMqDeV6h6e0oLst/KNdhpiO/ic5gR/4DX 7MNjowWkNQAi16CBKrrPjcETBNNISpmKWifHsOETF9us6zY8X/cq7EN+Ouut8g== From: "Paulo Alcantara (SUSE)" To: smfrench@gmail.com Cc: linux-cifs@vger.kernel.org, "Paulo Alcantara (SUSE)" Subject: [PATCH v3 08/11] cifs: Fix potential deadlock when updating vol in cifs_reconnect() Date: Tue, 26 Nov 2019 21:36:31 -0300 Message-Id: <20191127003634.14072-9-pc@cjr.nz> In-Reply-To: <20191127003634.14072-1-pc@cjr.nz> References: <20191127003634.14072-1-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 vol_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. Also turn vol_lock into a spinlock rather than a mutex. Signed-off-by: Paulo Alcantara (SUSE) --- fs/cifs/dfs_cache.c | 104 +++++++++++++++++++++++++++++--------------- 1 file changed, 69 insertions(+), 35 deletions(-) diff --git a/fs/cifs/dfs_cache.c b/fs/cifs/dfs_cache.c index 1d1f7c03931b..629190926197 100644 --- a/fs/cifs/dfs_cache.c +++ b/fs/cifs/dfs_cache.c @@ -52,12 +52,14 @@ struct vol_info { struct smb_vol smb_vol; char *mntdata; struct list_head list; + struct list_head rlist; + int vol_count; }; static struct kmem_cache *cache_slab __read_mostly; static struct workqueue_struct *dfscache_wq __read_mostly; -static int cache_ttl; +static atomic_t cache_ttl; static struct nls_table *cache_nlsc; /* @@ -69,7 +71,7 @@ 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_lock); static void refresh_cache_worker(struct work_struct *work); @@ -300,7 +302,7 @@ int dfs_cache_init(void) for (i = 0; i < CACHE_HTABLE_SIZE; i++) INIT_HLIST_HEAD(&cache_htable[i]); - cache_ttl = -1; + atomic_set(&cache_ttl, -1); cache_nlsc = load_nls_default(); cifs_dbg(FYI, "%s: initialized DFS referral cache\n", __func__); @@ -464,6 +466,7 @@ add_cache_entry(unsigned int hash, const char *path, const struct dfs_info3_param *refs, int numrefs) { struct cache_entry *ce; + int ttl; ce = alloc_cache_entry(path, refs, numrefs); if (IS_ERR(ce)) @@ -471,15 +474,16 @@ 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) { - cache_ttl = ce->ttl; - queue_delayed_work(dfscache_wq, &refresh_task, cache_ttl * HZ); + ttl = atomic_read(&cache_ttl); + if (ttl < 0) { + ttl = ce->ttl; + queue_delayed_work(dfscache_wq, &refresh_task, ttl * HZ); } else { - cache_ttl = min_t(int, cache_ttl, ce->ttl); - mod_delayed_work(dfscache_wq, &refresh_task, cache_ttl * HZ); + ttl = min_t(int, ttl, ce->ttl); + mod_delayed_work(dfscache_wq, &refresh_task, ttl * HZ); } - mutex_unlock(&vol_lock); + + atomic_set(&cache_ttl, ttl); return ce; } @@ -523,13 +527,16 @@ static inline void destroy_slab_cache(void) kmem_cache_destroy(cache_slab); } -static inline void free_vol(struct vol_info *vi) +/* Must be called with vol_lock held */ +static inline void put_vol(struct vol_info *vi) { - list_del(&vi->list); - kfree(vi->fullpath); - kfree(vi->mntdata); - cifs_cleanup_volume_info_contents(&vi->smb_vol); - kfree(vi); + if (!--vi->vol_count) { + list_del_init(&vi->list); + kfree(vi->fullpath); + kfree(vi->mntdata); + cifs_cleanup_volume_info_contents(&vi->smb_vol); + kfree(vi); + } } static inline void free_vol_list(void) @@ -537,7 +544,7 @@ 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); + put_vol(vi); } /** @@ -1156,10 +1163,12 @@ int dfs_cache_add_vol(char *mntdata, struct smb_vol *vol, const char *fullpath) goto err_free_fullpath; vi->mntdata = mntdata; + vi->vol_count++; - mutex_lock(&vol_lock); + spin_lock(&vol_lock); list_add_tail(&vi->list, &vol_list); - mutex_unlock(&vol_lock); + spin_unlock(&vol_lock); + return 0; err_free_fullpath: @@ -1169,7 +1178,8 @@ 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_lock held */ +static struct vol_info *find_vol(const char *fullpath) { struct vol_info *vi; @@ -1199,21 +1209,22 @@ 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_lock); vi = find_vol(fullpath); if (IS_ERR(vi)) { rc = PTR_ERR(vi); - goto out; + goto out_unlock; } cifs_dbg(FYI, "%s: updating volume info\n", __func__); memcpy(&vi->smb_vol.dstaddr, &server->dstaddr, sizeof(vi->smb_vol.dstaddr)); + rc = 0; -out: - mutex_unlock(&vol_lock); +out_unlock: + spin_unlock(&vol_lock); return rc; } @@ -1231,11 +1242,11 @@ void dfs_cache_del_vol(const char *fullpath) cifs_dbg(FYI, "%s: fullpath: %s\n", __func__, fullpath); - mutex_lock(&vol_lock); + spin_lock(&vol_lock); vi = find_vol(fullpath); if (!IS_ERR(vi)) - free_vol(vi); - mutex_unlock(&vol_lock); + put_vol(vi); + spin_unlock(&vol_lock); } /* Get all tcons that are within a DFS namespace and can be refreshed */ @@ -1449,27 +1460,50 @@ 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_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) { + vi->vol_count++; + list_add_tail(&vi->rlist, &vols); + put_tcp_server(server); + } + spin_unlock(&vol_lock); + + /* Walk through all TCONs and refresh any expired cache entry */ + list_for_each_entry_safe(vi, nvi, &vols, rlist) { + server = get_tcp_server(&vi->smb_vol); + 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); + spin_lock(&vol_lock); + put_vol(vi); + spin_unlock(&vol_lock); } - queue_delayed_work(dfscache_wq, &refresh_task, cache_ttl * HZ); - mutex_unlock(&vol_lock); + + queue_delayed_work(dfscache_wq, &refresh_task, + atomic_read(&cache_ttl) * HZ); }