cifs: don't block in dfs_cache_noreq_update_tgthint()

Avoid blocking in dfs_cache_noreq_update_tgthint() while reconnecting
servers or tcons as the cache refresh worker or new mounts might
already be updating their targets.

Move some more dfs related code out of connect.c while at it.

Signed-off-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Signed-off-by: Steve French <stfrench@microsoft.com>

4 files changed, 269 insertions, 274 deletions

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index db3a2b3ac497..41009ef7878f 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -529,9 +529,7 @@ static int reconnect_dfs_server(struct TCP_Server_Info *server)
 		mod_delayed_work(cifsiod_wq, &server->reconnect, 0);
 	} while (server->tcpStatus == CifsNeedReconnect);
 
-	if (target_hint)
-		dfs_cache_noreq_update_tgthint(refpath, target_hint);
-
+	dfs_cache_noreq_update_tgthint(refpath, target_hint);
 	dfs_cache_free_tgts(&tl);
 
 	/* Need to set up echo worker again once connection has been established */
@@ -4079,265 +4077,7 @@ cifs_prune_tlinks(struct work_struct *work)
 				TLINK_IDLE_EXPIRE);
 }
 
-#ifdef CONFIG_CIFS_DFS_UPCALL
-/* Update dfs referral path of superblock */
-static int update_server_fullpath(struct TCP_Server_Info *server, struct cifs_sb_info *cifs_sb,
-				  const char *target)
-{
-	int rc = 0;
-	size_t len = strlen(target);
-	char *refpath, *npath;
-
-	if (unlikely(len < 2 || *target != '\\'))
-		return -EINVAL;
-
-	if (target[1] == '\\') {
-		len += 1;
-		refpath = kmalloc(len, GFP_KERNEL);
-		if (!refpath)
-			return -ENOMEM;
-
-		scnprintf(refpath, len, "%s", target);
-	} else {
-		len += sizeof("\\");
-		refpath = kmalloc(len, GFP_KERNEL);
-		if (!refpath)
-			return -ENOMEM;
-
-		scnprintf(refpath, len, "\\%s", target);
-	}
-
-	npath = dfs_cache_canonical_path(refpath, cifs_sb->local_nls, cifs_remap(cifs_sb));
-	kfree(refpath);
-
-	if (IS_ERR(npath)) {
-		rc = PTR_ERR(npath);
-	} else {
-		mutex_lock(&server->refpath_lock);
-		kfree(server->leaf_fullpath);
-		server->leaf_fullpath = npath;
-		mutex_unlock(&server->refpath_lock);
-		server->current_fullpath = server->leaf_fullpath;
-	}
-	return rc;
-}
-
-static int target_share_matches_server(struct TCP_Server_Info *server, const char *tcp_host,
-				       size_t tcp_host_len, char *share, bool *target_match)
-{
-	int rc = 0;
-	const char *dfs_host;
-	size_t dfs_host_len;
-
-	*target_match = true;
-	extract_unc_hostname(share, &dfs_host, &dfs_host_len);
-
-	/* Check if hostnames or addresses match */
-	if (dfs_host_len != tcp_host_len || strncasecmp(dfs_host, tcp_host, dfs_host_len) != 0) {
-		cifs_dbg(FYI, "%s: %.*s doesn't match %.*s\n", __func__, (int)dfs_host_len,
-			 dfs_host, (int)tcp_host_len, tcp_host);
-		rc = match_target_ip(server, dfs_host, dfs_host_len, target_match);
-		if (rc)
-			cifs_dbg(VFS, "%s: failed to match target ip: %d\n", __func__, rc);
-	}
-	return rc;
-}
-
-static int __tree_connect_dfs_target(const unsigned int xid, struct cifs_tcon *tcon,
-				     struct cifs_sb_info *cifs_sb, char *tree, bool islink,
-				     struct dfs_cache_tgt_list *tl)
-{
-	int rc;
-	struct TCP_Server_Info *server = tcon->ses->server;
-	const struct smb_version_operations *ops = server->ops;
-	struct cifs_ses *root_ses = CIFS_DFS_ROOT_SES(tcon->ses);
-	struct cifs_tcon *ipc = root_ses->tcon_ipc;
-	char *share = NULL, *prefix = NULL;
-	const char *tcp_host;
-	size_t tcp_host_len;
-	struct dfs_cache_tgt_iterator *tit;
-	bool target_match;
-
-	extract_unc_hostname(server->hostname, &tcp_host, &tcp_host_len);
-
-	tit = dfs_cache_get_tgt_iterator(tl);
-	if (!tit) {
-		rc = -ENOENT;
-		goto out;
-	}
-
-	/* Try to tree connect to all dfs targets */
-	for (; tit; tit = dfs_cache_get_next_tgt(tl, tit)) {
-		const char *target = dfs_cache_get_tgt_name(tit);
-		struct dfs_cache_tgt_list ntl = DFS_CACHE_TGT_LIST_INIT(ntl);
-
-		kfree(share);
-		kfree(prefix);
-		share = prefix = NULL;
-
-		/* Check if share matches with tcp ses */
-		rc = dfs_cache_get_tgt_share(server->current_fullpath + 1, tit, &share, &prefix);
-		if (rc) {
-			cifs_dbg(VFS, "%s: failed to parse target share: %d\n", __func__, rc);
-			break;
-		}
-
-		rc = target_share_matches_server(server, tcp_host, tcp_host_len, share,
-						 &target_match);
-		if (rc)
-			break;
-		if (!target_match) {
-			rc = -EHOSTUNREACH;
-			continue;
-		}
-
-		if (ipc->need_reconnect) {
-			scnprintf(tree, MAX_TREE_SIZE, "\\\\%s\\IPC$", server->hostname);
-			rc = ops->tree_connect(xid, ipc->ses, tree, ipc, cifs_sb->local_nls);
-			if (rc)
-				break;
-		}
-
-		scnprintf(tree, MAX_TREE_SIZE, "\\%s", share);
-		if (!islink) {
-			rc = ops->tree_connect(xid, tcon->ses, tree, tcon, cifs_sb->local_nls);
-			break;
-		}
-		/*
-		 * If no dfs referrals were returned from link target, then just do a TREE_CONNECT
-		 * to it.  Otherwise, cache the dfs referral and then mark current tcp ses for
-		 * reconnect so either the demultiplex thread or the echo worker will reconnect to
-		 * newly resolved target.
-		 */
-		if (dfs_cache_find(xid, root_ses, cifs_sb->local_nls, cifs_remap(cifs_sb), target,
-				   NULL, &ntl)) {
-			rc = ops->tree_connect(xid, tcon->ses, tree, tcon, cifs_sb->local_nls);
-			if (rc)
-				continue;
-			rc = dfs_cache_noreq_update_tgthint(server->current_fullpath + 1, tit);
-			if (!rc)
-				rc = cifs_update_super_prepath(cifs_sb, prefix);
-		} else {
-			/* Target is another dfs share */
-			rc = update_server_fullpath(server, cifs_sb, target);
-			dfs_cache_free_tgts(tl);
-
-			if (!rc) {
-				rc = -EREMOTE;
-				list_replace_init(&ntl.tl_list, &tl->tl_list);
-			} else
-				dfs_cache_free_tgts(&ntl);
-		}
-		break;
-	}
-
-out:
-	kfree(share);
-	kfree(prefix);
-
-	return rc;
-}
-
-static int tree_connect_dfs_target(const unsigned int xid, struct cifs_tcon *tcon,
-				   struct cifs_sb_info *cifs_sb, char *tree, bool islink,
-				   struct dfs_cache_tgt_list *tl)
-{
-	int rc;
-	int num_links = 0;
-	struct TCP_Server_Info *server = tcon->ses->server;
-
-	do {
-		rc = __tree_connect_dfs_target(xid, tcon, cifs_sb, tree, islink, tl);
-		if (!rc || rc != -EREMOTE)
-			break;
-	} while (rc = -ELOOP, ++num_links < MAX_NESTED_LINKS);
-	/*
-	 * If we couldn't tree connect to any targets from last referral path, then retry from
-	 * original referral path.
-	 */
-	if (rc && server->current_fullpath != server->origin_fullpath) {
-		server->current_fullpath = server->origin_fullpath;
-		cifs_signal_cifsd_for_reconnect(server, true);
-	}
-
-	dfs_cache_free_tgts(tl);
-	return rc;
-}
-
-int cifs_tree_connect(const unsigned int xid, struct cifs_tcon *tcon, const struct nls_table *nlsc)
-{
-	int rc;
-	struct TCP_Server_Info *server = tcon->ses->server;
-	const struct smb_version_operations *ops = server->ops;
-	struct super_block *sb = NULL;
-	struct cifs_sb_info *cifs_sb;
-	struct dfs_cache_tgt_list tl = DFS_CACHE_TGT_LIST_INIT(tl);
-	char *tree;
-	struct dfs_info3_param ref = {0};
-
-	/* only send once per connect */
-	spin_lock(&tcon->tc_lock);
-	if (tcon->ses->ses_status != SES_GOOD ||
-	    (tcon->status != TID_NEW &&
-	    tcon->status != TID_NEED_TCON)) {
-		spin_unlock(&tcon->tc_lock);
-		return 0;
-	}
-	tcon->status = TID_IN_TCON;
-	spin_unlock(&tcon->tc_lock);
-
-	tree = kzalloc(MAX_TREE_SIZE, GFP_KERNEL);
-	if (!tree) {
-		rc = -ENOMEM;
-		goto out;
-	}
-
-	if (tcon->ipc) {
-		scnprintf(tree, MAX_TREE_SIZE, "\\\\%s\\IPC$", server->hostname);
-		rc = ops->tree_connect(xid, tcon->ses, tree, tcon, nlsc);
-		goto out;
-	}
-
-	sb = cifs_get_tcp_super(server);
-	if (IS_ERR(sb)) {
-		rc = PTR_ERR(sb);
-		cifs_dbg(VFS, "%s: could not find superblock: %d\n", __func__, rc);
-		goto out;
-	}
-
-	cifs_sb = CIFS_SB(sb);
-
-	/* If it is not dfs or there was no cached dfs referral, then reconnect to same share */
-	if (!server->current_fullpath ||
-	    dfs_cache_noreq_find(server->current_fullpath + 1, &ref, &tl)) {
-		rc = ops->tree_connect(xid, tcon->ses, tcon->tree_name, tcon, cifs_sb->local_nls);
-		goto out;
-	}
-
-	rc = tree_connect_dfs_target(xid, tcon, cifs_sb, tree, ref.server_type == DFS_TYPE_LINK,
-				     &tl);
-	free_dfs_info_param(&ref);
-
-out:
-	kfree(tree);
-	cifs_put_tcp_super(sb);
-
-	if (rc) {
-		spin_lock(&tcon->tc_lock);
-		if (tcon->status == TID_IN_TCON)
-			tcon->status = TID_NEED_TCON;
-		spin_unlock(&tcon->tc_lock);
-	} else {
-		spin_lock(&tcon->tc_lock);
-		if (tcon->status == TID_IN_TCON)
-			tcon->status = TID_GOOD;
-		spin_unlock(&tcon->tc_lock);
-		tcon->need_reconnect = false;
-	}
-
-	return rc;
-}
-#else
+#ifndef CONFIG_CIFS_DFS_UPCALL
 int cifs_tree_connect(const unsigned int xid, struct cifs_tcon *tcon, const struct nls_table *nlsc)
 {
 	int rc;
diff --git a/fs/cifs/dfs.c b/fs/cifs/dfs.c
index fbc8e880a1fe..5afabca654c1 100644
--- a/fs/cifs/dfs.c
+++ b/fs/cifs/dfs.c
@@ -284,3 +284,262 @@ int dfs_mount_share(struct cifs_mount_ctx *mnt_ctx, bool *isdfs)
 
 	return __dfs_mount_share(mnt_ctx);
 }
+
+/* Update dfs referral path of superblock */
+static int update_server_fullpath(struct TCP_Server_Info *server, struct cifs_sb_info *cifs_sb,
+				  const char *target)
+{
+	int rc = 0;
+	size_t len = strlen(target);
+	char *refpath, *npath;
+
+	if (unlikely(len < 2 || *target != '\\'))
+		return -EINVAL;
+
+	if (target[1] == '\\') {
+		len += 1;
+		refpath = kmalloc(len, GFP_KERNEL);
+		if (!refpath)
+			return -ENOMEM;
+
+		scnprintf(refpath, len, "%s", target);
+	} else {
+		len += sizeof("\\");
+		refpath = kmalloc(len, GFP_KERNEL);
+		if (!refpath)
+			return -ENOMEM;
+
+		scnprintf(refpath, len, "\\%s", target);
+	}
+
+	npath = dfs_cache_canonical_path(refpath, cifs_sb->local_nls, cifs_remap(cifs_sb));
+	kfree(refpath);
+
+	if (IS_ERR(npath)) {
+		rc = PTR_ERR(npath);
+	} else {
+		mutex_lock(&server->refpath_lock);
+		kfree(server->leaf_fullpath);
+		server->leaf_fullpath = npath;
+		mutex_unlock(&server->refpath_lock);
+		server->current_fullpath = server->leaf_fullpath;
+	}
+	return rc;
+}
+
+static int target_share_matches_server(struct TCP_Server_Info *server, const char *tcp_host,
+				       size_t tcp_host_len, char *share, bool *target_match)
+{
+	int rc = 0;
+	const char *dfs_host;
+	size_t dfs_host_len;
+
+	*target_match = true;
+	extract_unc_hostname(share, &dfs_host, &dfs_host_len);
+
+	/* Check if hostnames or addresses match */
+	if (dfs_host_len != tcp_host_len || strncasecmp(dfs_host, tcp_host, dfs_host_len) != 0) {
+		cifs_dbg(FYI, "%s: %.*s doesn't match %.*s\n", __func__, (int)dfs_host_len,
+			 dfs_host, (int)tcp_host_len, tcp_host);
+		rc = match_target_ip(server, dfs_host, dfs_host_len, target_match);
+		if (rc)
+			cifs_dbg(VFS, "%s: failed to match target ip: %d\n", __func__, rc);
+	}
+	return rc;
+}
+
+static int __tree_connect_dfs_target(const unsigned int xid, struct cifs_tcon *tcon,
+				     struct cifs_sb_info *cifs_sb, char *tree, bool islink,
+				     struct dfs_cache_tgt_list *tl)
+{
+	int rc;
+	struct TCP_Server_Info *server = tcon->ses->server;
+	const struct smb_version_operations *ops = server->ops;
+	struct cifs_ses *root_ses = CIFS_DFS_ROOT_SES(tcon->ses);
+	struct cifs_tcon *ipc = root_ses->tcon_ipc;
+	char *share = NULL, *prefix = NULL;
+	const char *tcp_host;
+	size_t tcp_host_len;
+	struct dfs_cache_tgt_iterator *tit;
+	bool target_match;
+
+	extract_unc_hostname(server->hostname, &tcp_host, &tcp_host_len);
+
+	tit = dfs_cache_get_tgt_iterator(tl);
+	if (!tit) {
+		rc = -ENOENT;
+		goto out;
+	}
+
+	/* Try to tree connect to all dfs targets */
+	for (; tit; tit = dfs_cache_get_next_tgt(tl, tit)) {
+		const char *target = dfs_cache_get_tgt_name(tit);
+		struct dfs_cache_tgt_list ntl = DFS_CACHE_TGT_LIST_INIT(ntl);
+
+		kfree(share);
+		kfree(prefix);
+		share = prefix = NULL;
+
+		/* Check if share matches with tcp ses */
+		rc = dfs_cache_get_tgt_share(server->current_fullpath + 1, tit, &share, &prefix);
+		if (rc) {
+			cifs_dbg(VFS, "%s: failed to parse target share: %d\n", __func__, rc);
+			break;
+		}
+
+		rc = target_share_matches_server(server, tcp_host, tcp_host_len, share,
+						 &target_match);
+		if (rc)
+			break;
+		if (!target_match) {
+			rc = -EHOSTUNREACH;
+			continue;
+		}
+
+		dfs_cache_noreq_update_tgthint(server->current_fullpath + 1, tit);
+
+		if (ipc->need_reconnect) {
+			scnprintf(tree, MAX_TREE_SIZE, "\\\\%s\\IPC$", server->hostname);
+			rc = ops->tree_connect(xid, ipc->ses, tree, ipc, cifs_sb->local_nls);
+			if (rc)
+				break;
+		}
+
+		scnprintf(tree, MAX_TREE_SIZE, "\\%s", share);
+		if (!islink) {
+			rc = ops->tree_connect(xid, tcon->ses, tree, tcon, cifs_sb->local_nls);
+			break;
+		}
+		/*
+		 * If no dfs referrals were returned from link target, then just do a TREE_CONNECT
+		 * to it.  Otherwise, cache the dfs referral and then mark current tcp ses for
+		 * reconnect so either the demultiplex thread or the echo worker will reconnect to
+		 * newly resolved target.
+		 */
+		if (dfs_cache_find(xid, root_ses, cifs_sb->local_nls, cifs_remap(cifs_sb), target,
+				   NULL, &ntl)) {
+			rc = ops->tree_connect(xid, tcon->ses, tree, tcon, cifs_sb->local_nls);
+			if (rc)
+				continue;
+
+			rc = cifs_update_super_prepath(cifs_sb, prefix);
+		} else {
+			/* Target is another dfs share */
+			rc = update_server_fullpath(server, cifs_sb, target);
+			dfs_cache_free_tgts(tl);
+
+			if (!rc) {
+				rc = -EREMOTE;
+				list_replace_init(&ntl.tl_list, &tl->tl_list);
+			} else
+				dfs_cache_free_tgts(&ntl);
+		}
+		break;
+	}
+
+out:
+	kfree(share);
+	kfree(prefix);
+
+	return rc;
+}
+
+static int tree_connect_dfs_target(const unsigned int xid, struct cifs_tcon *tcon,
+				   struct cifs_sb_info *cifs_sb, char *tree, bool islink,
+				   struct dfs_cache_tgt_list *tl)
+{
+	int rc;
+	int num_links = 0;
+	struct TCP_Server_Info *server = tcon->ses->server;
+
+	do {
+		rc = __tree_connect_dfs_target(xid, tcon, cifs_sb, tree, islink, tl);
+		if (!rc || rc != -EREMOTE)
+			break;
+	} while (rc = -ELOOP, ++num_links < MAX_NESTED_LINKS);
+	/*
+	 * If we couldn't tree connect to any targets from last referral path, then retry from
+	 * original referral path.
+	 */
+	if (rc && server->current_fullpath != server->origin_fullpath) {
+		server->current_fullpath = server->origin_fullpath;
+		cifs_signal_cifsd_for_reconnect(server, true);
+	}
+
+	dfs_cache_free_tgts(tl);
+	return rc;
+}
+
+int cifs_tree_connect(const unsigned int xid, struct cifs_tcon *tcon, const struct nls_table *nlsc)
+{
+	int rc;
+	struct TCP_Server_Info *server = tcon->ses->server;
+	const struct smb_version_operations *ops = server->ops;
+	struct super_block *sb = NULL;
+	struct cifs_sb_info *cifs_sb;
+	struct dfs_cache_tgt_list tl = DFS_CACHE_TGT_LIST_INIT(tl);
+	char *tree;
+	struct dfs_info3_param ref = {0};
+
+	/* only send once per connect */
+	spin_lock(&tcon->tc_lock);
+	if (tcon->ses->ses_status != SES_GOOD ||
+	    (tcon->status != TID_NEW &&
+	    tcon->status != TID_NEED_TCON)) {
+		spin_unlock(&tcon->tc_lock);
+		return 0;
+	}
+	tcon->status = TID_IN_TCON;
+	spin_unlock(&tcon->tc_lock);
+
+	tree = kzalloc(MAX_TREE_SIZE, GFP_KERNEL);
+	if (!tree) {
+		rc = -ENOMEM;
+		goto out;
+	}
+
+	if (tcon->ipc) {
+		scnprintf(tree, MAX_TREE_SIZE, "\\\\%s\\IPC$", server->hostname);
+		rc = ops->tree_connect(xid, tcon->ses, tree, tcon, nlsc);
+		goto out;
+	}
+
+	sb = cifs_get_tcp_super(server);
+	if (IS_ERR(sb)) {
+		rc = PTR_ERR(sb);
+		cifs_dbg(VFS, "%s: could not find superblock: %d\n", __func__, rc);
+		goto out;
+	}
+
+	cifs_sb = CIFS_SB(sb);
+
+	/* If it is not dfs or there was no cached dfs referral, then reconnect to same share */
+	if (!server->current_fullpath ||
+	    dfs_cache_noreq_find(server->current_fullpath + 1, &ref, &tl)) {
+		rc = ops->tree_connect(xid, tcon->ses, tcon->tree_name, tcon, cifs_sb->local_nls);
+		goto out;
+	}
+
+	rc = tree_connect_dfs_target(xid, tcon, cifs_sb, tree, ref.server_type == DFS_TYPE_LINK,
+				     &tl);
+	free_dfs_info_param(&ref);
+
+out:
+	kfree(tree);
+	cifs_put_tcp_super(sb);
+
+	if (rc) {
+		spin_lock(&tcon->tc_lock);
+		if (tcon->status == TID_IN_TCON)
+			tcon->status = TID_NEED_TCON;
+		spin_unlock(&tcon->tc_lock);
+	} else {
+		spin_lock(&tcon->tc_lock);
+		if (tcon->status == TID_IN_TCON)
+			tcon->status = TID_GOOD;
+		spin_unlock(&tcon->tc_lock);
+		tcon->need_reconnect = false;
+	}
+
+	return rc;
+}
diff --git a/fs/cifs/dfs_cache.c b/fs/cifs/dfs_cache.c
index cb83b86eafe6..43ad1176dcb9 100644
--- a/fs/cifs/dfs_cache.c
+++ b/fs/cifs/dfs_cache.c
@@ -1082,26 +1082,23 @@ out_free_path:
  *
  * Return zero if the target hint was updated successfully, otherwise non-zero.
  */
-int dfs_cache_noreq_update_tgthint(const char *path, const struct dfs_cache_tgt_iterator *it)
+void dfs_cache_noreq_update_tgthint(const char *path, const struct dfs_cache_tgt_iterator *it)
 {
-	int rc;
-	struct cache_entry *ce;
 	struct cache_dfs_tgt *t;
+	struct cache_entry *ce;
 
-	if (!it)
-		return -EINVAL;
+	if (!path || !it)
+		return;
 
 	cifs_dbg(FYI, "%s: path: %s\n", __func__, path);
 
-	down_write(&htable_rw_lock);
+	if (!down_write_trylock(&htable_rw_lock))
+		return;
 
 	ce = lookup_cache_entry(path);
-	if (IS_ERR(ce)) {
-		rc = PTR_ERR(ce);
+	if (IS_ERR(ce))
 		goto out_unlock;
-	}
 
-	rc = 0;
 	t = ce->tgthint;
 
 	if (unlikely(!strcasecmp(it->it_name, t->name)))
@@ -1118,7 +1115,6 @@ int dfs_cache_noreq_update_tgthint(const char *path, const struct dfs_cache_tgt_
 
 out_unlock:
 	up_write(&htable_rw_lock);
-	return rc;
 }
 
 /**
diff --git a/fs/cifs/dfs_cache.h b/fs/cifs/dfs_cache.h
index 52070d1df189..f7cff0be9327 100644
--- a/fs/cifs/dfs_cache.h
+++ b/fs/cifs/dfs_cache.h
@@ -38,7 +38,7 @@ int dfs_cache_noreq_find(const char *path, struct dfs_info3_param *ref,
 int dfs_cache_update_tgthint(const unsigned int xid, struct cifs_ses *ses,
 			     const struct nls_table *cp, int remap, const char *path,
 			     const struct dfs_cache_tgt_iterator *it);
-int dfs_cache_noreq_update_tgthint(const char *path, const struct dfs_cache_tgt_iterator *it);
+void dfs_cache_noreq_update_tgthint(const char *path, const struct dfs_cache_tgt_iterator *it);
 int dfs_cache_get_tgt_referral(const char *path, const struct dfs_cache_tgt_iterator *it,
 			       struct dfs_info3_param *ref);
 int dfs_cache_get_tgt_share(char *path, const struct dfs_cache_tgt_iterator *it, char **share,