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/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;