Commit 855982a5 authored by Paulo Alcantara's avatar Paulo Alcantara Committed by Steve French
Browse files

smb: client: relax session and tcon reconnect attempts 



When the client re-establishes connection to the server, it will queue
a worker thread that will attempt to reconnect sessions and tcons on
every two seconds, which is kinda overkill as it is a very common
scenario when having expired passwords or KRB5 TGT tickets, or deleted
shares.

Use an exponential backoff strategy to handle session/tcon reconnect
attempts in the worker thread to prevent the client from overloading
the system when it is very unlikely to re-establish any session/tcon
soon while client is idle.

Signed-off-by: default avatarPaulo Alcantara (Red Hat) <pc@manguebit.org>
Reviewed-by: default avatarDavid Howells <dhowells@redhat.com>
Cc: Pierguido Lambri <plambri@redhat.com>
Cc: linux-cifs@vger.kernel.org
Signed-off-by: default avatarSteve French <stfrench@microsoft.com>
parent 4ae4dde6

fs/smb/client/cifsglob.h

+21 −0
Original line number Diff line number Diff line
@@ -745,6 +745,7 @@ struct TCP_Server_Info { 
	struct session_key session_key;

	unsigned long lstrp; /* when we got last response from this server */

	unsigned long neg_start; /* when negotiate started (jiffies) */

	unsigned long reconn_delay; /* when resched session and tcon reconnect */

	struct cifs_secmech secmech; /* crypto sec mech functs, descriptors */

#define	CIFS_NEGFLAVOR_UNENCAP	1	/* wct == 17, but no ext_sec */

#define	CIFS_NEGFLAVOR_EXTENDED	2	/* wct == 17, ext_sec bit set */
@@ -2292,4 +2293,24 @@ struct cifs_calc_sig_ctx { 
	struct shash_desc *shash;

};



#define CIFS_RECONN_DELAY_SECS	30

#define CIFS_MAX_RECONN_DELAY	(4 * CIFS_RECONN_DELAY_SECS)



static inline void cifs_queue_server_reconn(struct TCP_Server_Info *server)

{

	if (!delayed_work_pending(&server->reconnect)) {

		WRITE_ONCE(server->reconn_delay, 0);

		mod_delayed_work(cifsiod_wq, &server->reconnect, 0);

	}

}



static inline void cifs_requeue_server_reconn(struct TCP_Server_Info *server)

{

	unsigned long delay = READ_ONCE(server->reconn_delay);



	delay = umin(delay + CIFS_RECONN_DELAY_SECS, CIFS_MAX_RECONN_DELAY);

	WRITE_ONCE(server->reconn_delay, delay);

	queue_delayed_work(cifsiod_wq, &server->reconnect, delay * HZ);

}



#endif	/* _CIFS_GLOB_H */

fs/smb/client/connect.c

+2 −2
Original line number Diff line number Diff line
@@ -425,7 +425,7 @@ static int __cifs_reconnect(struct TCP_Server_Info *server, 
			spin_unlock(&server->srv_lock);

			cifs_swn_reset_server_dstaddr(server);

			cifs_server_unlock(server);

			mod_delayed_work(cifsiod_wq, &server->reconnect, 0);

			cifs_queue_server_reconn(server);

		}

	} while (server->tcpStatus == CifsNeedReconnect);
@@ -564,7 +564,7 @@ static int reconnect_dfs_server(struct TCP_Server_Info *server) 
		spin_unlock(&server->srv_lock);

		cifs_swn_reset_server_dstaddr(server);

		cifs_server_unlock(server);

		mod_delayed_work(cifsiod_wq, &server->reconnect, 0);

		cifs_queue_server_reconn(server);

	} while (server->tcpStatus == CifsNeedReconnect);



	dfs_cache_noreq_update_tgthint(ref_path, target_hint);

fs/smb/client/smb2pdu.c

+3 −3
Original line number Diff line number Diff line
@@ -497,7 +497,7 @@ smb2_reconnect(__le16 smb2_command, struct cifs_tcon *tcon, 
	spin_unlock(&ses->ses_lock);



	if (smb2_command != SMB2_INTERNAL_CMD)

		mod_delayed_work(cifsiod_wq, &server->reconnect, 0);

		cifs_queue_server_reconn(server);



	atomic_inc(&tconInfoReconnectCount);

out:
@@ -4316,7 +4316,7 @@ void smb2_reconnect_server(struct work_struct *work) 
done:

	cifs_dbg(FYI, "Reconnecting tcons and channels finished\n");

	if (resched)

		queue_delayed_work(cifsiod_wq, &server->reconnect, 2 * HZ);

		cifs_requeue_server_reconn(server);

	mutex_unlock(&pserver->reconnect_mutex);



	/* now we can safely release srv struct */
@@ -4340,7 +4340,7 @@ SMB2_echo(struct TCP_Server_Info *server) 
	    server->ops->need_neg(server)) {

		spin_unlock(&server->srv_lock);

		/* No need to send echo on newly established connections */

		mod_delayed_work(cifsiod_wq, &server->reconnect, 0);

		cifs_queue_server_reconn(server);

		return rc;

	}

	spin_unlock(&server->srv_lock);