4 files changed, 203 insertions, 40 deletions

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 1b04d6ec14dd..3781eee9360a 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -220,7 +220,7 @@ cifs_reconnect(struct TCP_Server_Info *server)
 #ifdef CONFIG_CIFS_DFS_UPCALL
 	struct super_block *sb = NULL;
 	struct cifs_sb_info *cifs_sb = NULL;
-	struct dfs_cache_tgt_list tgt_list = {0};
+	struct dfs_cache_tgt_list tgt_list = DFS_CACHE_TGT_LIST_INIT(tgt_list);
 	struct dfs_cache_tgt_iterator *tgt_it = NULL;
 #endif
 
@@ -3130,7 +3130,7 @@ static int do_dfs_failover(const char *path, const char *full_path, struct cifs_
 {
 	int rc;
 	char *npath = NULL;
-	struct dfs_cache_tgt_list tgt_list = {0};
+	struct dfs_cache_tgt_list tgt_list = DFS_CACHE_TGT_LIST_INIT(tgt_list);
 	struct dfs_cache_tgt_iterator *tgt_it = NULL;
 	struct smb3_fs_context tmp_ctx = {NULL};
 
diff --git a/fs/cifs/dfs_cache.c b/fs/cifs/dfs_cache.c
index 7c1769714609..283745592844 100644
--- a/fs/cifs/dfs_cache.c
+++ b/fs/cifs/dfs_cache.c
@@ -19,6 +19,7 @@
 #include "cifs_debug.h"
 #include "cifs_unicode.h"
 #include "smb2glob.h"
+#include "dns_resolve.h"
 
 #include "dfs_cache.h"
 
@@ -911,6 +912,7 @@ static int get_targets(struct cache_entry *ce, struct dfs_cache_tgt_list *tl)
 
 err_free_it:
 	list_for_each_entry_safe(it, nit, head, it_list) {
+		list_del(&it->it_list);
 		kfree(it->it_name);
 		kfree(it);
 	}
@@ -1293,6 +1295,194 @@ 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)
+{
+	char unc[sizeof("\\\\") + SERVER_NAME_LENGTH] = {0};
+	const char *host;
+	size_t hostlen;
+	char *ip = NULL;
+	struct sockaddr sa;
+	bool match;
+	int rc;
+
+	if (strcasecmp(s1, s2))
+		return false;
+
+	/*
+	 * Resolve share's hostname and check if server address matches.  Otherwise just ignore it
+	 * as we could not have upcall to resolve hostname or failed to convert ip address.
+	 */
+	match = true;
+	extract_unc_hostname(s1, &host, &hostlen);
+	scnprintf(unc, sizeof(unc), "\\\\%.*s", (int)hostlen, host);
+
+	rc = dns_resolve_server_name_to_ip(unc, &ip, NULL);
+	if (rc < 0) {
+		cifs_dbg(FYI, "%s: could not resolve %.*s. assuming server address matches.\n",
+			 __func__, (int)hostlen, host);
+		return true;
+	}
+
+	if (!cifs_convert_address(&sa, ip, strlen(ip))) {
+		cifs_dbg(VFS, "%s: failed to convert address \'%s\'. skip address matching.\n",
+			 __func__, ip);
+	} else {
+		mutex_lock(&server->srv_mutex);
+		match = cifs_match_ipaddr((struct sockaddr *)&server->dstaddr, &sa);
+		mutex_unlock(&server->srv_mutex);
+	}
+
+	kfree(ip);
+	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 cifs_tcon *tcon, struct dfs_cache_tgt_list *tl,
+					 const struct dfs_info3_param *refs, int numrefs)
+{
+	struct dfs_cache_tgt_iterator *it;
+	int i;
+
+	for (it = dfs_cache_get_tgt_iterator(tl); it; it = dfs_cache_get_next_tgt(tl, it)) {
+		for (i = 0; i < numrefs; i++) {
+			if (target_share_equal(tcon->ses->server, dfs_cache_get_tgt_name(it),
+					       refs[i].node_name))
+				return;
+		}
+	}
+
+	cifs_dbg(FYI, "%s: no cached or matched targets. mark dfs share for reconnect.\n", __func__);
+	for (i = 0; i < tcon->ses->chan_count; i++) {
+		spin_lock(&GlobalMid_Lock);
+		if (tcon->ses->chans[i].server->tcpStatus != CifsExiting)
+			tcon->ses->chans[i].server->tcpStatus = CifsNeedReconnect;
+		spin_unlock(&GlobalMid_Lock);
+	}
+}
+
+/* Refresh dfs referral of tcon and mark it for reconnect if needed */
+static int refresh_tcon(struct cifs_ses **sessions, struct cifs_tcon *tcon, bool force_refresh)
+{
+	const char *path = tcon->dfs_path + 1;
+	struct cifs_ses *ses;
+	struct cache_entry *ce;
+	struct dfs_info3_param *refs = NULL;
+	int numrefs = 0;
+	bool needs_refresh = false;
+	struct dfs_cache_tgt_list tl = DFS_CACHE_TGT_LIST_INIT(tl);
+	int rc = 0;
+	unsigned int xid;
+
+	ses = find_ipc_from_server_path(sessions, path);
+	if (IS_ERR(ses)) {
+		cifs_dbg(FYI, "%s: could not find ipc session\n", __func__);
+		return PTR_ERR(ses);
+	}
+
+	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, &tl);
+		if (rc)
+			cifs_dbg(FYI, "%s: could not get dfs targets: %d\n", __func__, rc);
+	}
+	up_read(&htable_rw_lock);
+
+	if (!needs_refresh) {
+		rc = 0;
+		goto out;
+	}
+
+	xid = get_xid();
+	rc = get_dfs_referral(xid, ses, path, &refs, &numrefs);
+	free_xid(xid);
+
+	/* Create or update a cache entry with the new referral */
+	if (!rc) {
+		dump_refs(refs, numrefs);
+
+		down_write(&htable_rw_lock);
+		ce = lookup_cache_entry(path);
+		if (IS_ERR(ce))
+			add_cache_entry_locked(refs, numrefs);
+		else if (force_refresh || cache_entry_expired(ce))
+			update_cache_entry_locked(ce, refs, numrefs);
+		up_write(&htable_rw_lock);
+
+		mark_for_reconnect_if_needed(tcon, &tl, refs, numrefs);
+	}
+
+out:
+	dfs_cache_free_tgts(&tl);
+	free_dfs_info_array(refs, numrefs);
+	return rc;
+}
+
+/**
+ * dfs_cache_remount_fs - remount a DFS share
+ *
+ * Reconfigure dfs mount by forcing a new DFS referral and if the currently cached targets do not
+ * match any of the new targets, mark it for reconnect.
+ *
+ * @cifs_sb: cifs superblock.
+ *
+ * Return zero if remounted, otherwise non-zero.
+ */
+int dfs_cache_remount_fs(struct cifs_sb_info *cifs_sb)
+{
+	struct cifs_tcon *tcon;
+	struct mount_group *mg;
+	struct cifs_ses *sessions[CACHE_MAX_ENTRIES + 1] = {NULL};
+	int rc;
+
+	if (!cifs_sb || !cifs_sb->master_tlink)
+		return -EINVAL;
+
+	tcon = cifs_sb_master_tcon(cifs_sb);
+	if (!tcon->dfs_path) {
+		cifs_dbg(FYI, "%s: not a dfs tcon\n", __func__);
+		return 0;
+	}
+
+	if (uuid_is_null(&cifs_sb->dfs_mount_id)) {
+		cifs_dbg(FYI, "%s: tcon has no dfs mount group id\n", __func__);
+		return -EINVAL;
+	}
+
+	mutex_lock(&mount_group_list_lock);
+	mg = find_mount_group_locked(&cifs_sb->dfs_mount_id);
+	if (IS_ERR(mg)) {
+		mutex_unlock(&mount_group_list_lock);
+		cifs_dbg(FYI, "%s: tcon has ipc session to refresh referral\n", __func__);
+		return PTR_ERR(mg);
+	}
+	kref_get(&mg->refcount);
+	mutex_unlock(&mount_group_list_lock);
+
+	spin_lock(&mg->lock);
+	memcpy(&sessions, mg->sessions, mg->num_sessions * sizeof(mg->sessions[0]));
+	spin_unlock(&mg->lock);
+
+	/*
+	 * After reconnecting to a different server, unique ids won't match anymore, so we disable
+	 * serverino. This prevents dentry revalidation to think the dentry are stale (ESTALE).
+	 */
+	cifs_autodisable_serverino(cifs_sb);
+	/*
+	 * Force the use of prefix path to support failover on DFS paths that resolve to targets
+	 * that have different prefix paths.
+	 */
+	cifs_sb->mnt_cifs_flags |= CIFS_MOUNT_USE_PREFIX_PATH;
+	rc = refresh_tcon(sessions, tcon, true);
+
+	kref_put(&mg->refcount, mount_group_release);
+	return rc;
+}
+
 /*
  * Refresh all active dfs mounts regardless of whether they are in cache or not.
  * (cache can be cleared)
@@ -1303,7 +1493,6 @@ static void refresh_mounts(struct cifs_ses **sessions)
 	struct cifs_ses *ses;
 	struct cifs_tcon *tcon, *ntcon;
 	struct list_head tcons;
-	unsigned int xid;
 
 	INIT_LIST_HEAD(&tcons);
 
@@ -1321,44 +1510,8 @@ static void refresh_mounts(struct cifs_ses **sessions)
 	spin_unlock(&cifs_tcp_ses_lock);
 
 	list_for_each_entry_safe(tcon, ntcon, &tcons, ulist) {
-		const char *path = tcon->dfs_path + 1;
-		struct cache_entry *ce;
-		struct dfs_info3_param *refs = NULL;
-		int numrefs = 0;
-		bool needs_refresh = false;
-		int rc = 0;
-
 		list_del_init(&tcon->ulist);
-
-		ses = find_ipc_from_server_path(sessions, path);
-		if (IS_ERR(ses))
-			goto next_tcon;
-
-		down_read(&htable_rw_lock);
-		ce = lookup_cache_entry(path);
-		needs_refresh = IS_ERR(ce) || cache_entry_expired(ce);
-		up_read(&htable_rw_lock);
-
-		if (!needs_refresh)
-			goto next_tcon;
-
-		xid = get_xid();
-		rc = get_dfs_referral(xid, ses, path, &refs, &numrefs);
-		free_xid(xid);
-
-		/* Create or update a cache entry with the new referral */
-		if (!rc) {
-			down_write(&htable_rw_lock);
-			ce = lookup_cache_entry(path);
-			if (IS_ERR(ce))
-				add_cache_entry_locked(refs, numrefs);
-			else if (cache_entry_expired(ce))
-				update_cache_entry_locked(ce, refs, numrefs);
-			up_write(&htable_rw_lock);
-		}
-
-next_tcon:
-		free_dfs_info_array(refs, numrefs);
+		refresh_tcon(sessions, tcon, false);
 		cifs_put_tcon(tcon);
 	}
 }
diff --git a/fs/cifs/dfs_cache.h b/fs/cifs/dfs_cache.h
index b29d3ae64829..52070d1df189 100644
--- a/fs/cifs/dfs_cache.h
+++ b/fs/cifs/dfs_cache.h
@@ -13,6 +13,8 @@
 #include <linux/uuid.h>
 #include "cifsglob.h"
 
+#define DFS_CACHE_TGT_LIST_INIT(var) { .tl_numtgts = 0, .tl_list = LIST_HEAD_INIT((var).tl_list), }
+
 struct dfs_cache_tgt_list {
 	int tl_numtgts;
 	struct list_head tl_list;
@@ -44,6 +46,7 @@ int dfs_cache_get_tgt_share(char *path, const struct dfs_cache_tgt_iterator *it,
 void dfs_cache_put_refsrv_sessions(const uuid_t *mount_id);
 void dfs_cache_add_refsrv_session(const uuid_t *mount_id, struct cifs_ses *ses);
 char *dfs_cache_canonical_path(const char *path, const struct nls_table *cp, int remap);
+int dfs_cache_remount_fs(struct cifs_sb_info *cifs_sb);
 
 static inline struct dfs_cache_tgt_iterator *
 dfs_cache_get_next_tgt(struct dfs_cache_tgt_list *tl,
diff --git a/fs/cifs/fs_context.c b/fs/cifs/fs_context.c
index 553adfbcc22a..9a59d7ff9a11 100644
--- a/fs/cifs/fs_context.c
+++ b/fs/cifs/fs_context.c
@@ -13,6 +13,9 @@
 #include <linux/magic.h>
 #include <linux/security.h>
 #include <net/net_namespace.h>
+#ifdef CONFIG_CIFS_DFS_UPCALL
+#include "dfs_cache.h"
+#endif
 */
 
 #include <linux/ctype.h>
@@ -779,6 +782,10 @@ static int smb3_reconfigure(struct fs_context *fc)
 	smb3_cleanup_fs_context_contents(cifs_sb->ctx);
 	rc = smb3_fs_context_dup(cifs_sb->ctx, ctx);
 	smb3_update_mnt_flags(cifs_sb);
+#ifdef CONFIG_CIFS_DFS_UPCALL
+	if (!rc)
+		rc = dfs_cache_remount_fs(cifs_sb);
+#endif
 
 	return rc;
 }