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cifs: reinstate sharing of SMB sessions sans races

Browse source 
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>
This commit is contained in:
Jeff Layton 2008-11-14 13:53:46 -05:00 committed by Steve French
parent e7ddee9037
commit 14fbf50d69
7 changed files with 175 additions and 166 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

53
fs/cifs/cifs_debug.c
View file

@ -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;
@ -122,43 +122,45 @@ 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) ||
(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 @@ 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:");

17
fs/cifs/cifsfs.c
View file

@ -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_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 @@ 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

6
fs/cifs/cifsglob.h
View file

@ -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 */

1
fs/cifs/cifsproto.h
View file

@ -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 *);

24
fs/cifs/cifssmb.c
View file

@ -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,

224
fs/cifs/connect.c
View file

@ -144,23 +144,18 @@ cifs_reconnect(struct TCP_Server_Info *server)
/* 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 @@ cifs_demultiplex_thread(struct TCP_Server_Info *server)
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 @@ cifs_demultiplex_thread(struct TCP_Server_Info *server)
}
}
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 @@ cifs_demultiplex_thread(struct TCP_Server_Info *server)
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 @@ cifs_find_tcp_session(struct sockaddr *addr)
return NULL;
}
void
static void
cifs_put_tcp_session(struct TCP_Server_Info *server)
{
struct task_struct *task;
@ -1424,6 +1418,50 @@ cifs_put_tcp_session(struct TCP_Server_Info *server)
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 @@ cifs_mount(struct super_block *sb, struct cifs_sb_info *cifs_sb,
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 @@ cifs_mount(struct super_block *sb, struct cifs_sb_info *cifs_sb,
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 @@ cifs_mount(struct super_block *sb, struct cifs_sb_info *cifs_sb,
}
}
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 @@ cifs_mount(struct super_block *sb, struct cifs_sb_info *cifs_sb,
} 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 @@ cifs_mount(struct super_block *sb, struct cifs_sb_info *cifs_sb,
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 @@ cifs_mount(struct super_block *sb, struct cifs_sb_info *cifs_sb,
/* 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 @@ cifs_umount(struct super_block *sb, struct cifs_sb_info *cifs_sb)
}
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_umount(struct super_block *sb, struct cifs_sb_info *cifs_sb)
cifs_sb->prepathlen = 0;
cifs_sb->prepath = NULL;
kfree(tmp);
if (ses)
sesInfoFree(ses);
FreeXid(xid);
return rc;

16
fs/cifs/misc.c
View file

@ -75,12 +75,11 @@ sesInfoAlloc(void)
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 @@ sesInfoFree(struct cifsSesInfo *buf_to_free)
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 @@ header_assemble(struct smb_hdr *buffer, char smb_command /* command */ ,
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 @@ header_assemble(struct smb_hdr *buffer, char smb_command /* command */ ,
}
}
}
read_unlock(&GlobalSMBSeslock);
read_unlock(&cifs_tcp_ses_lock);
}
}
}