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cifs: Fix potential deadlock when updating vol in cifs_reconnect()
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) <pc@cjr.nz> Signed-off-by: Steve French <stfrench@microsoft.com>
This commit is contained in:
Paulo Alcantara (SUSE)
Steve French
parent
ff2f7fc082
commit
06d57378bc
@ -49,15 +49,20 @@ struct cache_entry {
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struct vol_info {
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char *fullpath;
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spinlock_t smb_vol_lock;
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struct smb_vol smb_vol;
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char *mntdata;
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struct list_head list;
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struct list_head rlist;
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struct kref refcnt;
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};
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static struct kmem_cache *cache_slab __read_mostly;
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static struct workqueue_struct *dfscache_wq __read_mostly;
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static int cache_ttl;
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static DEFINE_SPINLOCK(cache_ttl_lock);
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static struct nls_table *cache_nlsc;
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/*
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@ -69,7 +74,7 @@ static struct hlist_head cache_htable[CACHE_HTABLE_SIZE];
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static DEFINE_MUTEX(list_lock);
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static LIST_HEAD(vol_list);
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static DEFINE_MUTEX(vol_lock);
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static DEFINE_SPINLOCK(vol_list_lock);
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static void refresh_cache_worker(struct work_struct *work);
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@ -300,7 +305,6 @@ int dfs_cache_init(void)
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for (i = 0; i < CACHE_HTABLE_SIZE; i++)
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INIT_HLIST_HEAD(&cache_htable[i]);
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cache_ttl = -1;
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cache_nlsc = load_nls_default();
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cifs_dbg(FYI, "%s: initialized DFS referral cache\n", __func__);
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@ -471,15 +475,15 @@ add_cache_entry(unsigned int hash, const char *path,
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hlist_add_head_rcu(&ce->hlist, &cache_htable[hash]);
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mutex_lock(&vol_lock);
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if (cache_ttl < 0) {
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spin_lock(&cache_ttl_lock);
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if (!cache_ttl) {
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cache_ttl = ce->ttl;
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queue_delayed_work(dfscache_wq, &refresh_task, cache_ttl * HZ);
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} else {
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cache_ttl = min_t(int, cache_ttl, ce->ttl);
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mod_delayed_work(dfscache_wq, &refresh_task, cache_ttl * HZ);
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}
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mutex_unlock(&vol_lock);
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spin_unlock(&cache_ttl_lock);
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return ce;
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}
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@ -523,21 +527,32 @@ static inline void destroy_slab_cache(void)
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kmem_cache_destroy(cache_slab);
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}
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static inline void free_vol(struct vol_info *vi)
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static void __vol_release(struct vol_info *vi)
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{
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list_del(&vi->list);
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kfree(vi->fullpath);
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kfree(vi->mntdata);
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cifs_cleanup_volume_info_contents(&vi->smb_vol);
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kfree(vi);
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}
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static void vol_release(struct kref *kref)
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{
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struct vol_info *vi = container_of(kref, struct vol_info, refcnt);
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spin_lock(&vol_list_lock);
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list_del(&vi->list);
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spin_unlock(&vol_list_lock);
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__vol_release(vi);
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}
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static inline void free_vol_list(void)
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{
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struct vol_info *vi, *nvi;
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list_for_each_entry_safe(vi, nvi, &vol_list, list)
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free_vol(vi);
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list_for_each_entry_safe(vi, nvi, &vol_list, list) {
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list_del_init(&vi->list);
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__vol_release(vi);
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}
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}
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/**
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@ -1156,10 +1171,13 @@ int dfs_cache_add_vol(char *mntdata, struct smb_vol *vol, const char *fullpath)
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goto err_free_fullpath;
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vi->mntdata = mntdata;
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spin_lock_init(&vi->smb_vol_lock);
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kref_init(&vi->refcnt);
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mutex_lock(&vol_lock);
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spin_lock(&vol_list_lock);
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list_add_tail(&vi->list, &vol_list);
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mutex_unlock(&vol_lock);
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spin_unlock(&vol_list_lock);
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return 0;
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err_free_fullpath:
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@ -1169,7 +1187,8 @@ err_free_vi:
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return rc;
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}
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static inline struct vol_info *find_vol(const char *fullpath)
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/* Must be called with vol_list_lock held */
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static struct vol_info *find_vol(const char *fullpath)
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{
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struct vol_info *vi;
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@ -1191,7 +1210,6 @@ static inline struct vol_info *find_vol(const char *fullpath)
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*/
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int dfs_cache_update_vol(const char *fullpath, struct TCP_Server_Info *server)
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{
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int rc;
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struct vol_info *vi;
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if (!fullpath || !server)
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@ -1199,22 +1217,24 @@ int dfs_cache_update_vol(const char *fullpath, struct TCP_Server_Info *server)
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cifs_dbg(FYI, "%s: fullpath: %s\n", __func__, fullpath);
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mutex_lock(&vol_lock);
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spin_lock(&vol_list_lock);
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vi = find_vol(fullpath);
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if (IS_ERR(vi)) {
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rc = PTR_ERR(vi);
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goto out;
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spin_unlock(&vol_list_lock);
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return PTR_ERR(vi);
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}
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kref_get(&vi->refcnt);
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spin_unlock(&vol_list_lock);
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cifs_dbg(FYI, "%s: updating volume info\n", __func__);
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spin_lock(&vi->smb_vol_lock);
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memcpy(&vi->smb_vol.dstaddr, &server->dstaddr,
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sizeof(vi->smb_vol.dstaddr));
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rc = 0;
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spin_unlock(&vi->smb_vol_lock);
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out:
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mutex_unlock(&vol_lock);
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return rc;
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kref_put(&vi->refcnt, vol_release);
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return 0;
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}
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/**
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@ -1231,11 +1251,11 @@ void dfs_cache_del_vol(const char *fullpath)
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cifs_dbg(FYI, "%s: fullpath: %s\n", __func__, fullpath);
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mutex_lock(&vol_lock);
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spin_lock(&vol_list_lock);
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vi = find_vol(fullpath);
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if (!IS_ERR(vi))
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free_vol(vi);
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mutex_unlock(&vol_lock);
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spin_unlock(&vol_list_lock);
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kref_put(&vi->refcnt, vol_release);
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}
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/* Get all tcons that are within a DFS namespace and can be refreshed */
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@ -1449,27 +1469,52 @@ out:
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*/
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static void refresh_cache_worker(struct work_struct *work)
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{
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struct vol_info *vi;
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struct vol_info *vi, *nvi;
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struct TCP_Server_Info *server;
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LIST_HEAD(list);
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LIST_HEAD(vols);
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LIST_HEAD(tcons);
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struct cifs_tcon *tcon, *ntcon;
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mutex_lock(&vol_lock);
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/*
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* Find SMB volumes that are eligible (server->tcpStatus == CifsGood)
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* for refreshing.
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*/
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spin_lock(&vol_list_lock);
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list_for_each_entry(vi, &vol_list, list) {
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server = get_tcp_server(&vi->smb_vol);
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if (!server)
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continue;
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get_tcons(server, &list);
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list_for_each_entry_safe(tcon, ntcon, &list, ulist) {
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kref_get(&vi->refcnt);
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list_add_tail(&vi->rlist, &vols);
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put_tcp_server(server);
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}
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spin_unlock(&vol_list_lock);
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/* Walk through all TCONs and refresh any expired cache entry */
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list_for_each_entry_safe(vi, nvi, &vols, rlist) {
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spin_lock(&vi->smb_vol_lock);
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server = get_tcp_server(&vi->smb_vol);
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spin_unlock(&vi->smb_vol_lock);
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if (!server)
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goto next_vol;
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get_tcons(server, &tcons);
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list_for_each_entry_safe(tcon, ntcon, &tcons, ulist) {
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refresh_tcon(vi, tcon);
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list_del_init(&tcon->ulist);
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cifs_put_tcon(tcon);
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}
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put_tcp_server(server);
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next_vol:
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list_del_init(&vi->rlist);
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kref_put(&vi->refcnt, vol_release);
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}
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spin_lock(&cache_ttl_lock);
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queue_delayed_work(dfscache_wq, &refresh_task, cache_ttl * HZ);
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mutex_unlock(&vol_lock);
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spin_unlock(&cache_ttl_lock);
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}
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