smb: client: avoid unnecessary reconnects when refreshing referrals

Do not mark tcons for reconnect when current connection matches any of
the targets returned by new referral even when there is no cached
entry.
Signed-off-by: Paulo Alcantara (Red Hat) <pc@manguebit.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/smb/client/dfs_cache.c

@@ -1095,16 +1095,18 @@ int dfs_cache_get_tgt_share(char *path, const struct dfs_cache_tgt_iterator *it,
 	return 0;
 }
 
-static bool target_share_equal(struct TCP_Server_Info *server, const char *s1, const char *s2)
+static bool target_share_equal(struct cifs_tcon *tcon, const char *s1)
 {
-	char unc[sizeof("\\\\") + SERVER_NAME_LENGTH] = {0};
+	struct TCP_Server_Info *server = tcon->ses->server;
+	struct sockaddr_storage ss;
 	const char *host;
+	const char *s2 = &tcon->tree_name[1];
 	size_t hostlen;
-	struct sockaddr_storage ss;
+	char unc[sizeof("\\\\") + SERVER_NAME_LENGTH] = {0};
 	bool match;
 	int rc;
 
-	if (strcasecmp(s1, s2))
+	if (strcasecmp(s2, s1))
 		return false;
 
 	/*
@@ -1128,34 +1130,6 @@ static bool target_share_equal(struct TCP_Server_Info *server, const char *s1, c
 	return match;
 }
 
-/*
- * Mark dfs tcon for reconnecting when the currently connected tcon does not match any of the new
- * target shares in @refs.
- */
-static void mark_for_reconnect_if_needed(struct TCP_Server_Info *server,
-					 const char *path,
-					 struct dfs_cache_tgt_list *old_tl,
-					 struct dfs_cache_tgt_list *new_tl)
-{
-	struct dfs_cache_tgt_iterator *oit, *nit;
-
-	for (oit = dfs_cache_get_tgt_iterator(old_tl); oit;
-	     oit = dfs_cache_get_next_tgt(old_tl, oit)) {
-		for (nit = dfs_cache_get_tgt_iterator(new_tl); nit;
-		     nit = dfs_cache_get_next_tgt(new_tl, nit)) {
-			if (target_share_equal(server,
-					       dfs_cache_get_tgt_name(oit),
-					       dfs_cache_get_tgt_name(nit))) {
-				dfs_cache_noreq_update_tgthint(path, nit);
-				return;
-			}
-		}
-	}
-
-	cifs_dbg(FYI, "%s: no cached or matched targets. mark dfs share for reconnect.\n", __func__);
-	cifs_signal_cifsd_for_reconnect(server, true);
-}
-
 static bool is_ses_good(struct cifs_ses *ses)
 {
 	struct TCP_Server_Info *server = ses->server;
@@ -1172,41 +1146,35 @@ static bool is_ses_good(struct cifs_ses *ses)
 	return ret;
 }
 
-/* Refresh dfs referral of @ses and mark it for reconnect if needed */
-static void __refresh_ses_referral(struct cifs_ses *ses, bool force_refresh)
+static char *get_ses_refpath(struct cifs_ses *ses)
 {
 	struct TCP_Server_Info *server = ses->server;
-	DFS_CACHE_TGT_LIST(old_tl);
-	DFS_CACHE_TGT_LIST(new_tl);
-	bool needs_refresh = false;
-	struct cache_entry *ce;
-	unsigned int xid;
-	char *path = NULL;
-	int rc = 0;
-
-	xid = get_xid();
+	char *path = ERR_PTR(-ENOENT);
 
 	mutex_lock(&server->refpath_lock);
 	if (server->leaf_fullpath) {
 		path = kstrdup(server->leaf_fullpath + 1, GFP_ATOMIC);
 		if (!path)
-			rc = -ENOMEM;
+			path = ERR_PTR(-ENOMEM);
 	}
 	mutex_unlock(&server->refpath_lock);
-	if (!path)
-		goto out;
+	return path;
+}
 
-	down_read(&htable_rw_lock);
-	ce = lookup_cache_entry(path);
-	needs_refresh = force_refresh || IS_ERR(ce) || cache_entry_expired(ce);
-	if (!IS_ERR(ce)) {
-		rc = get_targets(ce, &old_tl);
-		cifs_dbg(FYI, "%s: get_targets: %d\n", __func__, rc);
-	}
-	up_read(&htable_rw_lock);
+/* Refresh dfs referral of @ses */
+static void refresh_ses_referral(struct cifs_ses *ses)
+{
+	struct cache_entry *ce;
+	unsigned int xid;
+	char *path;
+	int rc = 0;
 
-	if (!needs_refresh) {
-		rc = 0;
+	xid = get_xid();
+
+	path = get_ses_refpath(ses);
+	if (IS_ERR(path)) {
+		rc = PTR_ERR(path);
+		path = NULL;
 		goto out;
 	}
 
@@ -1217,29 +1185,106 @@ static void __refresh_ses_referral(struct cifs_ses *ses, bool force_refresh)
 		goto out;
 	}
 
-	ce = cache_refresh_path(xid, ses, path, true);
-	if (!IS_ERR(ce)) {
-		rc = get_targets(ce, &new_tl);
+	ce = cache_refresh_path(xid, ses, path, false);
+	if (!IS_ERR(ce))
 		up_read(&htable_rw_lock);
-		cifs_dbg(FYI, "%s: get_targets: %d\n", __func__, rc);
-		mark_for_reconnect_if_needed(server, path, &old_tl, &new_tl);
-	}
+	else
+		rc = PTR_ERR(ce);
 
 out:
 	free_xid(xid);
-	dfs_cache_free_tgts(&old_tl);
-	dfs_cache_free_tgts(&new_tl);
 	kfree(path);
 }
 
-static inline void refresh_ses_referral(struct cifs_ses *ses)
+static int __refresh_tcon_referral(struct cifs_tcon *tcon,
+				   const char *path,
+				   struct dfs_info3_param *refs,
+				   int numrefs, bool force_refresh)
 {
-	__refresh_ses_referral(ses, false);
+	struct cache_entry *ce;
+	bool reconnect = force_refresh;
+	int rc = 0;
+	int i;
+
+	if (unlikely(!numrefs))
+		return 0;
+
+	if (force_refresh) {
+		for (i = 0; i < numrefs; i++) {
+			/* TODO: include prefix paths in the matching */
+			if (target_share_equal(tcon, refs[i].node_name)) {
+				reconnect = false;
+				break;
+			}
+		}
+	}
+
+	down_write(&htable_rw_lock);
+	ce = lookup_cache_entry(path);
+	if (!IS_ERR(ce)) {
+		if (force_refresh || cache_entry_expired(ce))
+			rc = update_cache_entry_locked(ce, refs, numrefs);
+	} else if (PTR_ERR(ce) == -ENOENT) {
+		ce = add_cache_entry_locked(refs, numrefs);
+	}
+	up_write(&htable_rw_lock);
+
+	if (IS_ERR(ce))
+		rc = PTR_ERR(ce);
+	if (reconnect) {
+		cifs_tcon_dbg(FYI, "%s: mark for reconnect\n", __func__);
+		cifs_signal_cifsd_for_reconnect(tcon->ses->server, true);
+	}
+	return rc;
 }
 
-static inline void force_refresh_ses_referral(struct cifs_ses *ses)
+static void refresh_tcon_referral(struct cifs_tcon *tcon, bool force_refresh)
 {
-	__refresh_ses_referral(ses, true);
+	struct dfs_info3_param *refs = NULL;
+	struct cache_entry *ce;
+	struct cifs_ses *ses;
+	unsigned int xid;
+	bool needs_refresh;
+	char *path;
+	int numrefs = 0;
+	int rc = 0;
+
+	xid = get_xid();
+	ses = tcon->ses;
+
+	path = get_ses_refpath(ses);
+	if (IS_ERR(path)) {
+		rc = PTR_ERR(path);
+		path = NULL;
+		goto out;
+	}
+
+	down_read(&htable_rw_lock);
+	ce = lookup_cache_entry(path);
+	needs_refresh = force_refresh || IS_ERR(ce) || cache_entry_expired(ce);
+	if (!needs_refresh) {
+		up_read(&htable_rw_lock);
+		goto out;
+	}
+	up_read(&htable_rw_lock);
+
+	ses = CIFS_DFS_ROOT_SES(ses);
+	if (!is_ses_good(ses)) {
+		cifs_dbg(FYI, "%s: skip cache refresh due to disconnected ipc\n",
+			 __func__);
+		goto out;
+	}
+
+	rc = get_dfs_referral(xid, ses, path, &refs, &numrefs);
+	if (!rc) {
+		rc = __refresh_tcon_referral(tcon, path, refs,
+					     numrefs, force_refresh);
+	}
+
+out:
+	free_xid(xid);
+	kfree(path);
+	free_dfs_info_array(refs, numrefs);
 }
 
 /**
@@ -1280,7 +1325,7 @@ int dfs_cache_remount_fs(struct cifs_sb_info *cifs_sb)
 	 */
 	cifs_sb->mnt_cifs_flags |= CIFS_MOUNT_USE_PREFIX_PATH;
 
-	force_refresh_ses_referral(tcon->ses);
+	refresh_tcon_referral(tcon, true);
 	return 0;
 }
 
@@ -1291,9 +1336,11 @@ void dfs_cache_refresh(struct work_struct *work)
 	struct cifs_ses *ses;
 
 	tcon = container_of(work, struct cifs_tcon, dfs_cache_work.work);
+	ses = tcon->ses->dfs_root_ses;
 
-	for (ses = tcon->ses; ses; ses = ses->dfs_root_ses)
+	for (; ses; ses = ses->dfs_root_ses)
 		refresh_ses_referral(ses);
+	refresh_tcon_referral(tcon, false);
 
 	queue_delayed_work(dfscache_wq, &tcon->dfs_cache_work,
 			   atomic_read(&dfs_cache_ttl) * HZ);