CIFS: Process reconnects for SMB2 shares

Signed-off-by: Pavel Shilovsky <piastry@etersoft.ru>
Signed-off-by: Steve French <smfrench@gmail.com>

1 files changed, 126 insertions, 1 deletions

diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
index 1bf037ec5a9d..48c04b2832e2 100644
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -127,7 +127,132 @@ static int
 smb2_reconnect(__le16 smb2_command, struct cifs_tcon *tcon)
 {
         int rc = 0;
-        /* BB add missing code here */
+        struct nls_table *nls_codepage;
+        struct cifs_ses *ses;
+        struct TCP_Server_Info *server;
+
+        /*
+         * SMB2s NegProt, SessSetup, Logoff do not have tcon yet so
+         * check for tcp and smb session status done differently
+         * for those three - in the calling routine.
+         */
+        if (tcon == NULL)
+                return rc;
+
+        if (smb2_command == SMB2_TREE_CONNECT)
+                return rc;
+
+        if (tcon->tidStatus == CifsExiting) {
+                /*
+                 * only tree disconnect, open, and write,
+                 * (and ulogoff which does not have tcon)
+                 * are allowed as we start force umount.
+                 */
+                if ((smb2_command != SMB2_WRITE) &&
+                   (smb2_command != SMB2_CREATE) &&
+                   (smb2_command != SMB2_TREE_DISCONNECT)) {
+                        cFYI(1, "can not send cmd %d while umounting",
+                                smb2_command);
+                        return -ENODEV;
+                }
+        }
+        if ((!tcon->ses) || (tcon->ses->status == CifsExiting) ||
+            (!tcon->ses->server))
+                return -EIO;
+
+        ses = tcon->ses;
+        server = ses->server;
+
+        /*
+         * Give demultiplex thread up to 10 seconds to reconnect, should be
+         * greater than cifs socket timeout which is 7 seconds
+         */
+        while (server->tcpStatus == CifsNeedReconnect) {
+                /*
+                 * Return to caller for TREE_DISCONNECT and LOGOFF and CLOSE
+                 * here since they are implicitly done when session drops.
+                 */
+                switch (smb2_command) {
+                /*
+                 * BB Should we keep oplock break and add flush to exceptions?
+                 */
+                case SMB2_TREE_DISCONNECT:
+                case SMB2_CANCEL:
+                case SMB2_CLOSE:
+                case SMB2_OPLOCK_BREAK:
+                        return -EAGAIN;
+                }
+
+                wait_event_interruptible_timeout(server->response_q,
+                        (server->tcpStatus != CifsNeedReconnect), 10 * HZ);
+
+                /* are we still trying to reconnect? */
+                if (server->tcpStatus != CifsNeedReconnect)
+                        break;
+
+                /*
+                 * on "soft" mounts we wait once. Hard mounts keep
+                 * retrying until process is killed or server comes
+                 * back on-line
+                 */
+                if (!tcon->retry) {
+                        cFYI(1, "gave up waiting on reconnect in smb_init");
+                        return -EHOSTDOWN;
+                }
+        }
+
+        if (!tcon->ses->need_reconnect && !tcon->need_reconnect)
+                return rc;
+
+        nls_codepage = load_nls_default();
+
+        /*
+         * need to prevent multiple threads trying to simultaneously reconnect
+         * the same SMB session
+         */
+        mutex_lock(&tcon->ses->session_mutex);
+        rc = cifs_negotiate_protocol(0, tcon->ses);
+        if (!rc && tcon->ses->need_reconnect)
+                rc = cifs_setup_session(0, tcon->ses, nls_codepage);
+
+        if (rc || !tcon->need_reconnect) {
+                mutex_unlock(&tcon->ses->session_mutex);
+                goto out;
+        }
+
+        cifs_mark_open_files_invalid(tcon);
+        rc = SMB2_tcon(0, tcon->ses, tcon->treeName, tcon, nls_codepage);
+        mutex_unlock(&tcon->ses->session_mutex);
+        cFYI(1, "reconnect tcon rc = %d", rc);
+        if (rc)
+                goto out;
+        atomic_inc(&tconInfoReconnectCount);
+        /*
+         * BB FIXME add code to check if wsize needs update due to negotiated
+         * smb buffer size shrinking.
+         */
+out:
+        /*
+         * Check if handle based operation so we know whether we can continue
+         * or not without returning to caller to reset file handle.
+         */
+        /*
+         * BB Is flush done by server on drop of tcp session? Should we special
+         * case it and skip above?
+         */
+        switch (smb2_command) {
+        case SMB2_FLUSH:
+        case SMB2_READ:
+        case SMB2_WRITE:
+        case SMB2_LOCK:
+        case SMB2_IOCTL:
+        case SMB2_QUERY_DIRECTORY:
+        case SMB2_CHANGE_NOTIFY:
+        case SMB2_QUERY_INFO:
+        case SMB2_SET_INFO:
+                return -EAGAIN;
+        }
+        unload_nls(nls_codepage);
         return rc;
 }