Commit ee36a3b3 authored by Shyam Prasad N's avatar Shyam Prasad N Committed by Steve French
Browse files

cifs: make sure that channel scaling is done only once 



Following a successful cifs_tree_connect, we have the code
to scale up/down the number of channels in the session.
However, it is not protected by a lock today.

As a result, this code can be executed by several processes
that select the same channel. The core functions handle this
well, as they pick chan_lock. However, we've seen cases where
smb2_reconnect throws some warnings.

To fix that, this change introduces a flags bitmap inside the
cifs_ses structure. A new flag type is used to ensure that
only one process enters this section at any time.

Signed-off-by: default avatarShyam Prasad N <sprasad@microsoft.com>
Signed-off-by: default avatarSteve French <stfrench@microsoft.com>
parent 41bccc98

fs/smb/client/cifsglob.h

+3 −0
Original line number Diff line number Diff line
@@ -1032,6 +1032,8 @@ struct cifs_chan { 
	__u8 signkey[SMB3_SIGN_KEY_SIZE];

};



#define CIFS_SES_FLAG_SCALE_CHANNELS (0x1)



/*

 * Session structure.  One of these for each uid session with a particular host

 */
@@ -1064,6 +1066,7 @@ struct cifs_ses { 
	enum securityEnum sectype; /* what security flavor was specified? */

	bool sign;		/* is signing required? */

	bool domainAuto:1;

	unsigned int flags;

	__u16 session_flags;

	__u8 smb3signingkey[SMB3_SIGN_KEY_SIZE];

	__u8 smb3encryptionkey[SMB3_ENC_DEC_KEY_SIZE];

fs/smb/client/smb2pdu.c

+17 −3
Original line number Diff line number Diff line
@@ -399,6 +399,15 @@ smb2_reconnect(__le16 smb2_command, struct cifs_tcon *tcon, 
		goto out;

	}



	spin_lock(&ses->ses_lock);

	if (ses->flags & CIFS_SES_FLAG_SCALE_CHANNELS) {

		spin_unlock(&ses->ses_lock);

		mutex_unlock(&ses->session_mutex);

		goto skip_add_channels;

	}

	ses->flags |= CIFS_SES_FLAG_SCALE_CHANNELS;

	spin_unlock(&ses->ses_lock);



	if (!rc &&

	    (server->capabilities & SMB2_GLOBAL_CAP_MULTI_CHANNEL)) {

		mutex_unlock(&ses->session_mutex);
@@ -428,17 +437,22 @@ smb2_reconnect(__le16 smb2_command, struct cifs_tcon *tcon, 
		if (ses->chan_max > ses->chan_count &&

		    ses->iface_count &&

		    !SERVER_IS_CHAN(server)) {

			if (ses->chan_count == 1)

			if (ses->chan_count == 1) {

				cifs_server_dbg(VFS, "supports multichannel now\n");



			cifs_try_adding_channels(ses);

				queue_delayed_work(cifsiod_wq, &tcon->query_interfaces,

						 (SMB_INTERFACE_POLL_INTERVAL * HZ));

			}



			cifs_try_adding_channels(ses);

		}

	} else {

		mutex_unlock(&ses->session_mutex);

	}



skip_add_channels:

	spin_lock(&ses->ses_lock);

	ses->flags &= ~CIFS_SES_FLAG_SCALE_CHANNELS;

	spin_unlock(&ses->ses_lock);



	if (smb2_command != SMB2_INTERNAL_CMD)

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