Commit 14fbf50d authored by Jeff Layton's avatar Jeff Layton Committed by Steve French
Browse files

cifs: reinstate sharing of SMB sessions sans races 



We do this by abandoning the global list of SMB sessions and instead
moving to a per-server list. This entails adding a new list head to the
TCP_Server_Info struct. The refcounting for the cifsSesInfo is moved to
a non-atomic variable. We have to protect it by a lock anyway, so there's
no benefit to making it an atomic. The list and refcount are protected
by the global cifs_tcp_ses_lock.

The patch also adds a new routines to find and put SMB sessions and
that properly take and put references under the lock.

Signed-off-by: default avatarJeff Layton <jlayton@redhat.com>
Signed-off-by: default avatarSteve French <sfrench@us.ibm.com>
parent e7ddee90

fs/cifs/cifs_debug.c

+27 −26
Original line number Diff line number Diff line
@@ -107,9 +107,9 @@ void cifs_dump_mids(struct TCP_Server_Info *server) 
#ifdef CONFIG_PROC_FS

static int cifs_debug_data_proc_show(struct seq_file *m, void *v)

{

	struct list_head *tmp;

	struct list_head *tmp1;

	struct list_head *tmp, *tmp2, *tmp3;

	struct mid_q_entry *mid_entry;

	struct TCP_Server_Info *server;

	struct cifsSesInfo *ses;

	struct cifsTconInfo *tcon;

	int i;
@@ -122,11 +122,16 @@ static int cifs_debug_data_proc_show(struct seq_file *m, void *v) 
	seq_printf(m, "Servers:");



	i = 0;

	read_lock(&GlobalSMBSeslock);

	list_for_each(tmp, &GlobalSMBSessionList) {

	read_lock(&cifs_tcp_ses_lock);

	list_for_each(tmp, &cifs_tcp_ses_list) {

		server = list_entry(tmp, struct TCP_Server_Info,

				    tcp_ses_list);

		i++;

		ses = list_entry(tmp, struct cifsSesInfo, cifsSessionList);

		if ((ses->serverDomain == NULL) || (ses->serverOS == NULL) ||

		list_for_each(tmp2, &server->smb_ses_list) {

			ses = list_entry(tmp2, struct cifsSesInfo,

					 smb_ses_list);

			if ((ses->serverDomain == NULL) ||

				(ses->serverOS == NULL) ||

				(ses->serverNOS == NULL)) {

				seq_printf(m, "\nentry for %s not fully "

					   "displayed\n\t", ses->serverName);
@@ -136,29 +141,26 @@ static int cifs_debug_data_proc_show(struct seq_file *m, void *v) 
				    " %s  \n\tNOS: %s\tCapability: 0x%x\n\tSMB"

				    " session status: %d\t",

				i, ses->serverName, ses->serverDomain,

				atomic_read(&ses->inUse),

				ses->serverOS, ses->serverNOS,

				ses->ses_count, ses->serverOS, ses->serverNOS,

				ses->capabilities, ses->status);

			}

		if (ses->server) {

			seq_printf(m, "TCP status: %d\n\tLocal Users To "

				   "Server: %d SecMode: 0x%x Req On Wire: %d",

				ses->server->tcpStatus,

				ses->server->srv_count,

				ses->server->secMode,

				atomic_read(&ses->server->inFlight));

				   server->tcpStatus, server->srv_count,

				   server->secMode,

				   atomic_read(&server->inFlight));



#ifdef CONFIG_CIFS_STATS2

			seq_printf(m, " In Send: %d In MaxReq Wait: %d",

				atomic_read(&ses->server->inSend),

				atomic_read(&ses->server->num_waiters));

				atomic_read(&server->inSend),

				atomic_read(&server->num_waiters));

#endif



			seq_puts(m, "\nMIDs:\n");



			spin_lock(&GlobalMid_Lock);

			list_for_each(tmp1, &ses->server->pending_mid_q) {

				mid_entry = list_entry(tmp1, struct

			list_for_each(tmp3, &server->pending_mid_q) {

				mid_entry = list_entry(tmp3, struct

					mid_q_entry,

					qhead);

				seq_printf(m, "State: %d com: %d pid:"
@@ -171,9 +173,8 @@ static int cifs_debug_data_proc_show(struct seq_file *m, void *v) 
			}

			spin_unlock(&GlobalMid_Lock);

		}



	}

	read_unlock(&GlobalSMBSeslock);

	read_unlock(&cifs_tcp_ses_lock);

	seq_putc(m, '\n');



	seq_puts(m, "Shares:");

fs/cifs/cifsfs.c

+8 −9
Original line number Diff line number Diff line
@@ -1031,24 +1031,24 @@ static int cifs_oplock_thread(void *dummyarg) 
static int cifs_dnotify_thread(void *dummyarg)

{

	struct list_head *tmp;

	struct cifsSesInfo *ses;

	struct TCP_Server_Info *server;



	do {

		if (try_to_freeze())

			continue;

		set_current_state(TASK_INTERRUPTIBLE);

		schedule_timeout(15*HZ);

		read_lock(&GlobalSMBSeslock);

		/* check if any stuck requests that need

		   to be woken up and wakeq so the

		   thread can wake up and error out */

		list_for_each(tmp, &GlobalSMBSessionList) {

			ses = list_entry(tmp, struct cifsSesInfo,

				cifsSessionList);

			if (ses->server && atomic_read(&ses->server->inFlight))

				wake_up_all(&ses->server->response_q);

		}

		read_unlock(&GlobalSMBSeslock);

		read_lock(&cifs_tcp_ses_lock);

		list_for_each(tmp, &cifs_tcp_ses_list) {

			server = list_entry(tmp, struct TCP_Server_Info,

					 tcp_ses_list);

			if (atomic_read(&server->inFlight))

				wake_up_all(&server->response_q);

		}

		read_unlock(&cifs_tcp_ses_lock);

	} while (!kthread_should_stop());



	return 0;
@@ -1060,7 +1060,6 @@ init_cifs(void) 
	int rc = 0;

	cifs_proc_init();

	INIT_LIST_HEAD(&cifs_tcp_ses_list);

	INIT_LIST_HEAD(&GlobalSMBSessionList); /* BB to be removed by jl */

	INIT_LIST_HEAD(&GlobalTreeConnectionList); /* BB to be removed by jl */

	INIT_LIST_HEAD(&GlobalOplock_Q);

#ifdef CONFIG_CIFS_EXPERIMENTAL

fs/cifs/cifsglob.h

+2 −4
Original line number Diff line number Diff line
@@ -195,14 +195,14 @@ struct cifsUidInfo { 
 * Session structure.  One of these for each uid session with a particular host

 */

struct cifsSesInfo {

	struct list_head cifsSessionList;

	struct list_head smb_ses_list;

	struct list_head tcon_list;

	struct semaphore sesSem;

#if 0

	struct cifsUidInfo *uidInfo;	/* pointer to user info */

#endif

	struct TCP_Server_Info *server;	/* pointer to server info */

	atomic_t inUse; /* # of mounts (tree connections) on this ses */

	int ses_count;		/* reference counter */

	enum statusEnum status;

	unsigned overrideSecFlg;  /* if non-zero override global sec flags */

	__u16 ipc_tid;		/* special tid for connection to IPC share */
@@ -602,8 +602,6 @@ GLOBAL_EXTERN struct list_head cifs_tcp_ses_list; 


/* protects cifs_tcp_ses_list and srv_count for each tcp session */

GLOBAL_EXTERN rwlock_t		cifs_tcp_ses_lock;



GLOBAL_EXTERN struct list_head GlobalSMBSessionList; /* BB to be removed by jl*/

GLOBAL_EXTERN struct list_head GlobalTreeConnectionList; /* BB to be removed */

GLOBAL_EXTERN rwlock_t GlobalSMBSeslock;  /* protects list inserts on 3 above */

fs/cifs/cifsproto.h

+0 −1
Original line number Diff line number Diff line
@@ -102,7 +102,6 @@ extern void acl_to_uid_mode(struct inode *inode, const char *path, 
			    const __u16 *pfid);

extern int mode_to_acl(struct inode *inode, const char *path, __u64);



extern void cifs_put_tcp_session(struct TCP_Server_Info *server);

extern int cifs_mount(struct super_block *, struct cifs_sb_info *, char *,

			const char *);

extern int cifs_umount(struct super_block *, struct cifs_sb_info *);

fs/cifs/cifssmb.c

+7 −15
Original line number Diff line number Diff line
@@ -799,20 +799,16 @@ CIFSSMBLogoff(const int xid, struct cifsSesInfo *ses) 
	int rc = 0;



	cFYI(1, ("In SMBLogoff for session disconnect"));

	if (ses)

		down(&ses->sesSem);

	else

		return -EIO;



	atomic_dec(&ses->inUse);

	if (atomic_read(&ses->inUse) > 0) {

		up(&ses->sesSem);

		return -EBUSY;

	}



	if (ses->server == NULL)

	/*

	 * BB: do we need to check validity of ses and server? They should

	 * always be valid since we have an active reference. If not, that

	 * should probably be a BUG()

	 */

	if (!ses || !ses->server)

		return -EIO;



	down(&ses->sesSem);

	if (ses->need_reconnect)

		goto session_already_dead; /* no need to send SMBlogoff if uid

					      already closed due to reconnect */
@@ -833,10 +829,6 @@ CIFSSMBLogoff(const int xid, struct cifsSesInfo *ses) 
	pSMB->AndXCommand = 0xFF;

	rc = SendReceiveNoRsp(xid, ses, (struct smb_hdr *) pSMB, 0);

session_already_dead:

	if (ses->server) {

		cifs_put_tcp_session(ses->server);

		rc = 0;

	}

	up(&ses->sesSem);



	/* if session dead then we do not need to do ulogoff,

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