From: "Paulo Alcantara (SUSE)" pc@cjr.nz
commit 06d57378bcc9b2c33640945174842115593795d1 upstream.
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 Signed-off-by: Rishabh Bhatnagar risbhat@amazon.com --- 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 1efba8ee86bf..cf9267cf42e7 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); }