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: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
diff --git a/fs/cifs/cifs_debug.c b/fs/cifs/cifs_debug.c
index 40b5108..59841a6 100644
--- a/fs/cifs/cifs_debug.c
+++ b/fs/cifs/cifs_debug.c
@@ -107,9 +107,9 @@
#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;
@@ -122,43 +122,45 @@
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) ||
- (ses->serverNOS == NULL)) {
- seq_printf(m, "\nentry for %s not fully "
- "displayed\n\t", ses->serverName);
- } else {
- seq_printf(m,
+ 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);
+ } else {
+ seq_printf(m,
"\n%d) Name: %s Domain: %s Mounts: %d OS:"
" %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: %d SecMode: 0x%x Req On Wire: %d",
+ 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 @@
}
spin_unlock(&GlobalMid_Lock);
}
-
}
- read_unlock(&GlobalSMBSeslock);
+ read_unlock(&cifs_tcp_ses_lock);
seq_putc(m, '\n');
seq_puts(m, "Shares:");
diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 2946dab..a1e9662 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -1031,24 +1031,24 @@
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_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(&GlobalSMBSeslock);
+ read_unlock(&cifs_tcp_ses_lock);
} while (!kthread_should_stop());
return 0;
@@ -1060,7 +1060,6 @@
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
diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 313f7bf..631a99f 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -195,14 +195,14 @@
* 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 @@
/* 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 */
diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
index 0250a99..6f21ecb 100644
--- a/fs/cifs/cifsproto.h
+++ b/fs/cifs/cifsproto.h
@@ -102,7 +102,6 @@
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 *);
diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
index cd9e9a1..9c95617 100644
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -799,20 +799,16 @@
int rc = 0;
cFYI(1, ("In SMBLogoff for session disconnect"));
- if (ses)
- down(&ses->sesSem);
- else
+
+ /*
+ * 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;
- atomic_dec(&ses->inUse);
- if (atomic_read(&ses->inUse) > 0) {
- up(&ses->sesSem);
- return -EBUSY;
- }
-
- if (ses->server == NULL)
- 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 @@
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,
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index a031425..44130e0 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -144,23 +144,18 @@
/* before reconnecting the tcp session, mark the smb session (uid)
and the tid bad so they are not used until reconnected */
- read_lock(&GlobalSMBSeslock);
- list_for_each(tmp, &GlobalSMBSessionList) {
- ses = list_entry(tmp, struct cifsSesInfo, cifsSessionList);
- if (ses->server) {
- if (ses->server == server) {
- ses->need_reconnect = true;
- ses->ipc_tid = 0;
- }
- }
- /* else tcp and smb sessions need reconnection */
+ read_lock(&cifs_tcp_ses_lock);
+ list_for_each(tmp, &server->smb_ses_list) {
+ ses = list_entry(tmp, struct cifsSesInfo, smb_ses_list);
+ ses->need_reconnect = true;
+ ses->ipc_tid = 0;
}
+ read_unlock(&cifs_tcp_ses_lock);
list_for_each(tmp, &GlobalTreeConnectionList) {
tcon = list_entry(tmp, struct cifsTconInfo, cifsConnectionList);
if ((tcon->ses) && (tcon->ses->server == server))
tcon->need_reconnect = true;
}
- read_unlock(&GlobalSMBSeslock);
/* do not want to be sending data on a socket we are freeing */
down(&server->tcpSem);
if (server->ssocket) {
@@ -696,29 +691,29 @@
if (smallbuf) /* no sense logging a debug message if NULL */
cifs_small_buf_release(smallbuf);
- read_lock(&GlobalSMBSeslock);
+ /*
+ * BB: we shouldn't have to do any of this. It shouldn't be
+ * possible to exit from the thread with active SMB sessions
+ */
+ read_lock(&cifs_tcp_ses_lock);
if (list_empty(&server->pending_mid_q)) {
/* loop through server session structures attached to this and
mark them dead */
- list_for_each(tmp, &GlobalSMBSessionList) {
- ses =
- list_entry(tmp, struct cifsSesInfo,
- cifsSessionList);
- if (ses->server == server) {
- ses->status = CifsExiting;
- ses->server = NULL;
- }
+ list_for_each(tmp, &server->smb_ses_list) {
+ ses = list_entry(tmp, struct cifsSesInfo,
+ smb_ses_list);
+ ses->status = CifsExiting;
+ ses->server = NULL;
}
- read_unlock(&GlobalSMBSeslock);
+ read_unlock(&cifs_tcp_ses_lock);
} else {
/* although we can not zero the server struct pointer yet,
since there are active requests which may depnd on them,
mark the corresponding SMB sessions as exiting too */
- list_for_each(tmp, &GlobalSMBSessionList) {
+ list_for_each(tmp, &server->smb_ses_list) {
ses = list_entry(tmp, struct cifsSesInfo,
- cifsSessionList);
- if (ses->server == server)
- ses->status = CifsExiting;
+ smb_ses_list);
+ ses->status = CifsExiting;
}
spin_lock(&GlobalMid_Lock);
@@ -733,7 +728,7 @@
}
}
spin_unlock(&GlobalMid_Lock);
- read_unlock(&GlobalSMBSeslock);
+ read_unlock(&cifs_tcp_ses_lock);
/* 1/8th of sec is more than enough time for them to exit */
msleep(125);
}
@@ -755,14 +750,13 @@
if there are any pointing to this (e.g
if a crazy root user tried to kill cifsd
kernel thread explicitly this might happen) */
- write_lock(&GlobalSMBSeslock);
- list_for_each(tmp, &GlobalSMBSessionList) {
- ses = list_entry(tmp, struct cifsSesInfo,
- cifsSessionList);
- if (ses->server == server)
- ses->server = NULL;
+ /* BB: This shouldn't be necessary, see above */
+ read_lock(&cifs_tcp_ses_lock);
+ list_for_each(tmp, &server->smb_ses_list) {
+ ses = list_entry(tmp, struct cifsSesInfo, smb_ses_list);
+ ses->server = NULL;
}
- write_unlock(&GlobalSMBSeslock);
+ read_unlock(&cifs_tcp_ses_lock);
kfree(server->hostname);
task_to_wake = xchg(&server->tsk, NULL);
@@ -1401,7 +1395,7 @@
return NULL;
}
-void
+static void
cifs_put_tcp_session(struct TCP_Server_Info *server)
{
struct task_struct *task;
@@ -1424,6 +1418,50 @@
force_sig(SIGKILL, task);
}
+static struct cifsSesInfo *
+cifs_find_smb_ses(struct TCP_Server_Info *server, char *username)
+{
+ struct list_head *tmp;
+ struct cifsSesInfo *ses;
+
+ write_lock(&cifs_tcp_ses_lock);
+ list_for_each(tmp, &server->smb_ses_list) {
+ ses = list_entry(tmp, struct cifsSesInfo, smb_ses_list);
+ if (strncmp(ses->userName, username, MAX_USERNAME_SIZE))
+ continue;
+
+ ++ses->ses_count;
+ write_unlock(&cifs_tcp_ses_lock);
+ return ses;
+ }
+ write_unlock(&cifs_tcp_ses_lock);
+ return NULL;
+}
+
+static void
+cifs_put_smb_ses(struct cifsSesInfo *ses)
+{
+ int xid;
+ struct TCP_Server_Info *server = ses->server;
+
+ write_lock(&cifs_tcp_ses_lock);
+ if (--ses->ses_count > 0) {
+ write_unlock(&cifs_tcp_ses_lock);
+ return;
+ }
+
+ list_del_init(&ses->smb_ses_list);
+ write_unlock(&cifs_tcp_ses_lock);
+
+ if (ses->status == CifsGood) {
+ xid = GetXid();
+ CIFSSMBLogoff(xid, ses);
+ _FreeXid(xid);
+ }
+ sesInfoFree(ses);
+ cifs_put_tcp_session(server);
+}
+
int
get_dfs_path(int xid, struct cifsSesInfo *pSesInfo, const char *old_path,
const struct nls_table *nls_codepage, unsigned int *pnum_referrals,
@@ -1958,7 +1996,6 @@
struct sockaddr_in6 *sin_server6 = (struct sockaddr_in6 *) &addr;
struct smb_vol volume_info;
struct cifsSesInfo *pSesInfo = NULL;
- struct cifsSesInfo *existingCifsSes = NULL;
struct cifsTconInfo *tcon = NULL;
struct TCP_Server_Info *srvTcp = NULL;
@@ -2112,6 +2149,7 @@
volume_info.target_rfc1001_name, 16);
srvTcp->sequence_number = 0;
INIT_LIST_HEAD(&srvTcp->tcp_ses_list);
+ INIT_LIST_HEAD(&srvTcp->smb_ses_list);
++srvTcp->srv_count;
write_lock(&cifs_tcp_ses_lock);
list_add(&srvTcp->tcp_ses_list,
@@ -2120,10 +2158,16 @@
}
}
- if (existingCifsSes) {
- pSesInfo = existingCifsSes;
+ pSesInfo = cifs_find_smb_ses(srvTcp, volume_info.username);
+ if (pSesInfo) {
cFYI(1, ("Existing smb sess found (status=%d)",
pSesInfo->status));
+ /*
+ * The existing SMB session already has a reference to srvTcp,
+ * so we can put back the extra one we got before
+ */
+ cifs_put_tcp_session(srvTcp);
+
down(&pSesInfo->sesSem);
if (pSesInfo->need_reconnect) {
cFYI(1, ("Session needs reconnect"));
@@ -2134,41 +2178,44 @@
} else if (!rc) {
cFYI(1, ("Existing smb sess not found"));
pSesInfo = sesInfoAlloc();
- if (pSesInfo == NULL)
+ if (pSesInfo == NULL) {
rc = -ENOMEM;
- else {
- pSesInfo->server = srvTcp;
- sprintf(pSesInfo->serverName, "%u.%u.%u.%u",
- NIPQUAD(sin_server->sin_addr.s_addr));
+ goto mount_fail_check;
}
- if (!rc) {
- /* volume_info.password freed at unmount */
- if (volume_info.password) {
- pSesInfo->password = volume_info.password;
- /* set to NULL to prevent freeing on exit */
- volume_info.password = NULL;
- }
- if (volume_info.username)
- strncpy(pSesInfo->userName,
- volume_info.username,
- MAX_USERNAME_SIZE);
- if (volume_info.domainname) {
- int len = strlen(volume_info.domainname);
- pSesInfo->domainName =
- kmalloc(len + 1, GFP_KERNEL);
- if (pSesInfo->domainName)
- strcpy(pSesInfo->domainName,
- volume_info.domainname);
- }
- pSesInfo->linux_uid = volume_info.linux_uid;
- pSesInfo->overrideSecFlg = volume_info.secFlg;
- down(&pSesInfo->sesSem);
- /* BB FIXME need to pass vol->secFlgs BB */
- rc = cifs_setup_session(xid, pSesInfo,
- cifs_sb->local_nls);
- up(&pSesInfo->sesSem);
+ /* new SMB session uses our srvTcp ref */
+ pSesInfo->server = srvTcp;
+ sprintf(pSesInfo->serverName, "%u.%u.%u.%u",
+ NIPQUAD(sin_server->sin_addr.s_addr));
+
+ write_lock(&cifs_tcp_ses_lock);
+ list_add(&pSesInfo->smb_ses_list, &srvTcp->smb_ses_list);
+ write_unlock(&cifs_tcp_ses_lock);
+
+ /* volume_info.password freed at unmount */
+ if (volume_info.password) {
+ pSesInfo->password = volume_info.password;
+ /* set to NULL to prevent freeing on exit */
+ volume_info.password = NULL;
}
+ if (volume_info.username)
+ strncpy(pSesInfo->userName, volume_info.username,
+ MAX_USERNAME_SIZE);
+ if (volume_info.domainname) {
+ int len = strlen(volume_info.domainname);
+ pSesInfo->domainName = kmalloc(len + 1, GFP_KERNEL);
+ if (pSesInfo->domainName)
+ strcpy(pSesInfo->domainName,
+ volume_info.domainname);
+ }
+ pSesInfo->linux_uid = volume_info.linux_uid;
+ pSesInfo->overrideSecFlg = volume_info.secFlg;
+ down(&pSesInfo->sesSem);
+
+ /* BB FIXME need to pass vol->secFlgs BB */
+ rc = cifs_setup_session(xid, pSesInfo,
+ cifs_sb->local_nls);
+ up(&pSesInfo->sesSem);
}
/* search for existing tcon to this server share */
@@ -2209,11 +2256,9 @@
tcon->Flags));
}
}
- if (!rc) {
- atomic_inc(&pSesInfo->inUse);
- tcon->seal = volume_info.seal;
- } else
+ if (rc)
goto mount_fail_check;
+ tcon->seal = volume_info.seal;
}
/* we can have only one retry value for a connection
@@ -2234,29 +2279,19 @@
/* BB FIXME fix time_gran to be larger for LANMAN sessions */
sb->s_time_gran = 100;
-/* on error free sesinfo and tcon struct if needed */
mount_fail_check:
+ /* on error free sesinfo and tcon struct if needed */
if (rc) {
/* If find_unc succeeded then rc == 0 so we can not end */
/* up accidently freeing someone elses tcon struct */
if (tcon)
tconInfoFree(tcon);
- if (existingCifsSes == NULL) {
- if (pSesInfo) {
- if ((pSesInfo->server) &&
- (pSesInfo->status == CifsGood))
- CIFSSMBLogoff(xid, pSesInfo);
- else {
- cFYI(1, ("No session or bad tcon"));
- if (pSesInfo->server)
- cifs_put_tcp_session(
- pSesInfo->server);
- }
- sesInfoFree(pSesInfo);
- /* pSesInfo = NULL; */
- }
- }
+ /* should also end up putting our tcp session ref if needed */
+ if (pSesInfo)
+ cifs_put_smb_ses(pSesInfo);
+ else
+ cifs_put_tcp_session(srvTcp);
} else {
atomic_inc(&tcon->useCount);
cifs_sb->tcon = tcon;
@@ -3551,16 +3586,7 @@
}
DeleteTconOplockQEntries(cifs_sb->tcon);
tconInfoFree(cifs_sb->tcon);
- if ((ses) && (ses->server)) {
- /* save off task so we do not refer to ses later */
- cFYI(1, ("About to do SMBLogoff "));
- rc = CIFSSMBLogoff(xid, ses);
- if (rc == -EBUSY) {
- FreeXid(xid);
- return 0;
- }
- } else
- cFYI(1, ("No session or bad tcon"));
+ cifs_put_smb_ses(ses);
}
cifs_sb->tcon = NULL;
@@ -3568,8 +3594,6 @@
cifs_sb->prepathlen = 0;
cifs_sb->prepath = NULL;
kfree(tmp);
- if (ses)
- sesInfoFree(ses);
FreeXid(xid);
return rc;
diff --git a/fs/cifs/misc.c b/fs/cifs/misc.c
index 88786ba..46c8c7b 100644
--- a/fs/cifs/misc.c
+++ b/fs/cifs/misc.c
@@ -75,12 +75,11 @@
ret_buf = kzalloc(sizeof(struct cifsSesInfo), GFP_KERNEL);
if (ret_buf) {
- write_lock(&GlobalSMBSeslock);
atomic_inc(&sesInfoAllocCount);
ret_buf->status = CifsNew;
- list_add(&ret_buf->cifsSessionList, &GlobalSMBSessionList);
+ ++ret_buf->ses_count;
+ INIT_LIST_HEAD(&ret_buf->smb_ses_list);
init_MUTEX(&ret_buf->sesSem);
- write_unlock(&GlobalSMBSeslock);
}
return ret_buf;
}
@@ -93,10 +92,7 @@
return;
}
- write_lock(&GlobalSMBSeslock);
atomic_dec(&sesInfoAllocCount);
- list_del(&buf_to_free->cifsSessionList);
- write_unlock(&GlobalSMBSeslock);
kfree(buf_to_free->serverOS);
kfree(buf_to_free->serverDomain);
kfree(buf_to_free->serverNOS);
@@ -350,9 +346,9 @@
if (current->fsuid != treeCon->ses->linux_uid) {
cFYI(1, ("Multiuser mode and UID "
"did not match tcon uid"));
- read_lock(&GlobalSMBSeslock);
- list_for_each(temp_item, &GlobalSMBSessionList) {
- ses = list_entry(temp_item, struct cifsSesInfo, cifsSessionList);
+ read_lock(&cifs_tcp_ses_lock);
+ list_for_each(temp_item, &treeCon->ses->server->smb_ses_list) {
+ ses = list_entry(temp_item, struct cifsSesInfo, smb_ses_list);
if (ses->linux_uid == current->fsuid) {
if (ses->server == treeCon->ses->server) {
cFYI(1, ("found matching uid substitute right smb_uid"));
@@ -364,7 +360,7 @@
}
}
}
- read_unlock(&GlobalSMBSeslock);
+ read_unlock(&cifs_tcp_ses_lock);
}
}
}