cifs: commands that are retried should have replay flag set

MS-SMB2 states that the header flag SMB2_FLAGS_REPLAY_OPERATION
needs to be set when a command needs to be retried, so that
the server is aware that this is a replay for an operation that
appeared before.

This can be very important, for example, for state changing
operations and opens which get retried following a reconnect;
since the client maybe unaware of the status of the previous
open.

This is particularly important for multichannel scenario, since
disconnection of one connection does not mean that the session
is lost. The requests can be replayed on another channel.

This change also makes use of exponential back-off before replays
and also limits the number of retries to "retrans" mount option
value.

Also, this change does not modify the read/write codepath.

Signed-off-by: Shyam Prasad N <sprasad@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

1 files changed, 19 insertions, 4 deletions

diff --git a/fs/smb/client/cached_dir.c b/fs/smb/client/cached_dir.c
index 5730c65ffb40..1daeb5714faa 100644
--- a/fs/smb/client/cached_dir.c
+++ b/fs/smb/client/cached_dir.c
@@ -145,21 +145,27 @@ int open_cached_dir(unsigned int xid, struct cifs_tcon *tcon,
 	struct cached_fid *cfid;
 	struct cached_fids *cfids;
 	const char *npath;
+	int retries = 0, cur_sleep = 1;
 
 	if (tcon == NULL || tcon->cfids == NULL || tcon->nohandlecache ||
 	    is_smb1_server(tcon->ses->server) || (dir_cache_timeout == 0))
 		return -EOPNOTSUPP;
 
 	ses = tcon->ses;
-	server = cifs_pick_channel(ses);
 	cfids = tcon->cfids;
 
-	if (!server->ops->new_lease_key)
-		return -EIO;
-
 	if (cifs_sb->root == NULL)
 		return -ENOENT;
 
+replay_again:
+	/* reinitialize for possible replay */
+	flags = 0;
+	oplock = SMB2_OPLOCK_LEVEL_II;
+	server = cifs_pick_channel(ses);
+
+	if (!server->ops->new_lease_key)
+		return -EIO;
+
 	utf16_path = cifs_convert_path_to_utf16(path, cifs_sb);
 	if (!utf16_path)
 		return -ENOMEM;
@@ -268,6 +274,11 @@ int open_cached_dir(unsigned int xid, struct cifs_tcon *tcon,
 	 */
 	cfid->has_lease = true;
 
+	if (retries) {
+		smb2_set_replay(server, &rqst[0]);
+		smb2_set_replay(server, &rqst[1]);
+	}
+
 	rc = compound_send_recv(xid, ses, server,
 				flags, 2, rqst,
 				resp_buftype, rsp_iov);
@@ -368,6 +379,10 @@ out:
 	}
 	kfree(utf16_path);
 
+	if (is_replayable_error(rc) &&
+	    smb2_should_replay(tcon, &retries, &cur_sleep))
+		goto replay_again;
+
 	return rc;
 }