cifs: do not share tcp sessions of dfs connections

Make sure that we do not share tcp sessions of dfs mounts when
mounting regular shares that connect to same server.  DFS connections
rely on a single instance of tcp in order to do failover properly in
cifs_reconnect().

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

diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index ade7080f7eaa89ca429de5bfc6da02967e68cfd7..c0bfc2f01030df4d1615f4866d4ad9a0d782cddf 100644 (file)
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -693,6 +693,9 @@ struct TCP_Server_Info {
        bool use_swn_dstaddr;
        struct sockaddr_storage swn_dstaddr;
 #endif
+#ifdef CONFIG_CIFS_DFS_UPCALL
+       bool is_dfs_conn; /* if a dfs connection */
+#endif
 };
 
 struct cifs_credits {

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 6b6c3e341b42891214817f7c6cb228ed5d919601..1b04d6ec14ddac7d0f8aa4f86fd7898b1ff3d808 100644 (file)
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -1268,6 +1268,16 @@ cifs_find_tcp_session(struct smb3_fs_context *ctx)
 
        spin_lock(&cifs_tcp_ses_lock);
        list_for_each_entry(server, &cifs_tcp_ses_list, tcp_ses_list) {
+#ifdef CONFIG_CIFS_DFS_UPCALL
+               /*
+                * DFS failover implementation in cifs_reconnect() requires unique tcp sessions for
+                * DFS connections to do failover properly, so avoid sharing them with regular
+                * shares or even links that may connect to same server but having completely
+                * different failover targets.
+                */
+               if (server->is_dfs_conn)
+                       continue;
+#endif
                /*
                 * Skip ses channels since they're only handled in lower layers
                 * (e.g. cifs_send_recv).
@@ -2968,6 +2978,23 @@ static int mount_setup_tlink(struct cifs_sb_info *cifs_sb, struct cifs_ses *ses,
 }
 
 #ifdef CONFIG_CIFS_DFS_UPCALL
+static int mount_get_dfs_conns(struct smb3_fs_context *ctx, struct cifs_sb_info *cifs_sb,
+                              unsigned int *xid, struct TCP_Server_Info **nserver,
+                              struct cifs_ses **nses, struct cifs_tcon **ntcon)
+{
+       int rc;
+
+       ctx->nosharesock = true;
+       rc = mount_get_conns(ctx, cifs_sb, xid, nserver, nses, ntcon);
+       if (*nserver) {
+               cifs_dbg(FYI, "%s: marking tcp session as a dfs connection\n", __func__);
+               spin_lock(&cifs_tcp_ses_lock);
+               (*nserver)->is_dfs_conn = true;
+               spin_unlock(&cifs_tcp_ses_lock);
+       }
+       return rc;
+}
+
 /*
  * cifs_build_path_to_root returns full path to root when we do not have an
  * existing connection (tcon)
@@ -3163,7 +3190,7 @@ static int do_dfs_failover(const char *path, const char *full_path, struct cifs_
                         tmp_ctx.prepath);
 
                mount_put_conns(cifs_sb, *xid, *server, *ses, *tcon);
-               rc = mount_get_conns(&tmp_ctx, cifs_sb, xid, server, ses, tcon);
+               rc = mount_get_dfs_conns(&tmp_ctx, cifs_sb, xid, server, ses, tcon);
                if (!rc || (*server && *ses)) {
                        /*
                         * We were able to connect to new target server. Update current context with
@@ -3462,7 +3489,12 @@ int cifs_mount(struct cifs_sb_info *cifs_sb, struct smb3_fs_context *ctx)
                        goto error;
        }
 
-       ctx->nosharesock = true;
+       mount_put_conns(cifs_sb, xid, server, ses, tcon);
+       /*
+        * Ignore error check here because we may failover to other targets from cached a
+        * referral.
+        */
+       (void)mount_get_dfs_conns(ctx, cifs_sb, &xid, &server, &ses, &tcon);
 
        /* Get path of DFS root */
        ref_path = build_unc_path_to_root(ctx, cifs_sb, false);
@@ -3491,7 +3523,7 @@ int cifs_mount(struct cifs_sb_info *cifs_sb, struct smb3_fs_context *ctx)
                /* Connect to new DFS target only if we were redirected */
                if (oldmnt != cifs_sb->ctx->mount_options) {
                        mount_put_conns(cifs_sb, xid, server, ses, tcon);
-                       rc = mount_get_conns(ctx, cifs_sb, &xid, &server, &ses, &tcon);
+                       rc = mount_get_dfs_conns(ctx, cifs_sb, &xid, &server, &ses, &tcon);
                }
                if (rc && !server && !ses) {
                        /* Failed to connect. Try to connect to other targets in the referral. */