[PATCH AUTOSEL 5.18 64/68] cifs: fix potential deadlock in direct reclaim

From: Sasha Levin
Date: Tue Jun 07 2022 - 15:06:59 EST

From: Vincent Whitchurch <vincent.whitchurch@xxxxxxxx>

[ Upstream commit cc391b694ff085f62f133e6b8f864d43a8e69dfd ]

The srv_mutex is used during writeback so cifs should ensure that
allocations done when that mutex is held are done with GFP_NOFS, to
avoid having direct reclaim ending up waiting for the same mutex and
causing a deadlock. This is detected by lockdep with the splat below:

======================================================
WARNING: possible circular locking dependency detected
5.18.0 #70 Not tainted
------------------------------------------------------
kswapd0/49 is trying to acquire lock:
ffff8880195782e0 (&tcp_ses->srv_mutex){+.+.}-{3:3}, at: compound_send_recv

but task is already holding lock:
ffffffffa98e66c0 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #1 (fs_reclaim){+.+.}-{0:0}:
fs_reclaim_acquire
kmem_cache_alloc_trace
__request_module
crypto_alg_mod_lookup
crypto_alloc_tfm_node
crypto_alloc_shash
cifs_alloc_hash
smb311_crypto_shash_allocate
smb311_update_preauth_hash
compound_send_recv
cifs_send_recv
SMB2_negotiate
smb2_negotiate
cifs_negotiate_protocol
cifs_get_smb_ses
cifs_mount
cifs_smb3_do_mount
smb3_get_tree
vfs_get_tree
path_mount
__x64_sys_mount
do_syscall_64
entry_SYSCALL_64_after_hwframe

-> #0 (&tcp_ses->srv_mutex){+.+.}-{3:3}:
__lock_acquire
lock_acquire
__mutex_lock
mutex_lock_nested
compound_send_recv
cifs_send_recv
SMB2_write
smb2_sync_write
cifs_write
cifs_writepage_locked
cifs_writepage
shrink_page_list
shrink_lruvec
shrink_node
balance_pgdat
kswapd
kthread
ret_from_fork

other info that might help us debug this:

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(fs_reclaim);
lock(&tcp_ses->srv_mutex);
lock(fs_reclaim);
lock(&tcp_ses->srv_mutex);

*** DEADLOCK ***

1 lock held by kswapd0/49:
#0: ffffffffa98e66c0 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat

stack backtrace:
CPU: 2 PID: 49 Comm: kswapd0 Not tainted 5.18.0 #70
Call Trace:
<TASK>
dump_stack_lvl
dump_stack
print_circular_bug.cold
check_noncircular
__lock_acquire
lock_acquire
__mutex_lock
mutex_lock_nested
compound_send_recv
cifs_send_recv
SMB2_write
smb2_sync_write
cifs_write
cifs_writepage_locked
cifs_writepage
shrink_page_list
shrink_lruvec
shrink_node
balance_pgdat
kswapd
kthread
ret_from_fork
</TASK>

Fix this by using the memalloc_nofs_save/restore APIs around the places
where the srv_mutex is held. Do this in a wrapper function for the
lock/unlock of the srv_mutex, and rename the srv_mutex to avoid missing
call sites in the conversion.

Note that there is another lockdep warning involving internal crypto
locks, which was masked by this problem and is visible after this fix,
see the discussion in this thread:

https://lore.kernel.org/all/20220523123755.GA13668@xxxxxxxx/

Link: https://lore.kernel.org/r/CANT5p=rqcYfYMVHirqvdnnca4Mo+JQSw5Qu12v=kPfpk5yhhmg@xxxxxxxxxxxxxx/
Reported-by: Shyam Prasad N <nspmangalore@xxxxxxxxx>
Suggested-by: Lars Persson <larper@xxxxxxxx>
Reviewed-by: Ronnie Sahlberg <lsahlber@xxxxxxxxxx>
Reviewed-by: Enzo Matsumiya <ematsumiya@xxxxxxx>
Signed-off-by: Vincent Whitchurch <vincent.whitchurch@xxxxxxxx>
Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
fs/cifs/cifs_swn.c | 4 ++--
fs/cifs/cifsencrypt.c | 8 ++++----
fs/cifs/cifsglob.h | 20 +++++++++++++++++++-
fs/cifs/connect.c | 26 +++++++++++++-------------
fs/cifs/dfs_cache.c | 4 ++--
fs/cifs/sess.c | 6 +++---
fs/cifs/smb1ops.c | 6 +++---
fs/cifs/smb2pdu.c | 6 +++---
fs/cifs/smbdirect.c | 4 ++--
fs/cifs/transport.c | 40 ++++++++++++++++++++--------------------
10 files changed, 71 insertions(+), 53 deletions(-)

diff --git a/fs/cifs/cifs_swn.c b/fs/cifs/cifs_swn.c
index 180c234c2f46..1e4c7cc5287f 100644
--- a/fs/cifs/cifs_swn.c
+++ b/fs/cifs/cifs_swn.c
@@ -465,7 +465,7 @@ static int cifs_swn_reconnect(struct cifs_tcon *tcon, struct sockaddr_storage *a
int ret = 0;

/* Store the reconnect address */
- mutex_lock(&tcon->ses->server->srv_mutex);
+ cifs_server_lock(tcon->ses->server);
if (cifs_sockaddr_equal(&tcon->ses->server->dstaddr, addr))
goto unlock;

@@ -501,7 +501,7 @@ static int cifs_swn_reconnect(struct cifs_tcon *tcon, struct sockaddr_storage *a
cifs_signal_cifsd_for_reconnect(tcon->ses->server, false);

unlock:
- mutex_unlock(&tcon->ses->server->srv_mutex);
+ cifs_server_unlock(tcon->ses->server);

return ret;
}
diff --git a/fs/cifs/cifsencrypt.c b/fs/cifs/cifsencrypt.c
index 0912d8bbbac1..663cb9db4908 100644
--- a/fs/cifs/cifsencrypt.c
+++ b/fs/cifs/cifsencrypt.c
@@ -236,9 +236,9 @@ int cifs_verify_signature(struct smb_rqst *rqst,
cpu_to_le32(expected_sequence_number);
cifs_pdu->Signature.Sequence.Reserved = 0;

- mutex_lock(&server->srv_mutex);
+ cifs_server_lock(server);
rc = cifs_calc_signature(rqst, server, what_we_think_sig_should_be);
- mutex_unlock(&server->srv_mutex);
+ cifs_server_unlock(server);

if (rc)
return rc;
@@ -626,7 +626,7 @@ setup_ntlmv2_rsp(struct cifs_ses *ses, const struct nls_table *nls_cp)

memcpy(ses->auth_key.response + baselen, tiblob, tilen);

- mutex_lock(&ses->server->srv_mutex);
+ cifs_server_lock(ses->server);

rc = cifs_alloc_hash("hmac(md5)",
&ses->server->secmech.hmacmd5,
@@ -678,7 +678,7 @@ setup_ntlmv2_rsp(struct cifs_ses *ses, const struct nls_table *nls_cp)
cifs_dbg(VFS, "%s: Could not generate md5 hash\n", __func__);

unlock:
- mutex_unlock(&ses->server->srv_mutex);
+ cifs_server_unlock(ses->server);
setup_ntlmv2_rsp_ret:
kfree(tiblob);

diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 8de977c359b1..719d419a0a06 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -16,6 +16,7 @@
#include <linux/mempool.h>
#include <linux/workqueue.h>
#include <linux/utsname.h>
+#include <linux/sched/mm.h>
#include <linux/netfs.h>
#include "cifs_fs_sb.h"
#include "cifsacl.h"
@@ -621,7 +622,8 @@ struct TCP_Server_Info {
unsigned int in_flight; /* number of requests on the wire to server */
unsigned int max_in_flight; /* max number of requests that were on wire */
spinlock_t req_lock; /* protect the two values above */
- struct mutex srv_mutex;
+ struct mutex _srv_mutex;
+ unsigned int nofs_flag;
struct task_struct *tsk;
char server_GUID[16];
__u16 sec_mode;
@@ -736,6 +738,22 @@ struct TCP_Server_Info {
#endif
};

+static inline void cifs_server_lock(struct TCP_Server_Info *server)
+{
+ unsigned int nofs_flag = memalloc_nofs_save();
+
+ mutex_lock(&server->_srv_mutex);
+ server->nofs_flag = nofs_flag;
+}
+
+static inline void cifs_server_unlock(struct TCP_Server_Info *server)
+{
+ unsigned int nofs_flag = server->nofs_flag;
+
+ mutex_unlock(&server->_srv_mutex);
+ memalloc_nofs_restore(nofs_flag);
+}
+
struct cifs_credits {
unsigned int value;
unsigned int instance;
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 42e14f408856..5226f975d8e4 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -148,7 +148,7 @@ static void cifs_resolve_server(struct work_struct *work)
struct TCP_Server_Info *server = container_of(work,
struct TCP_Server_Info, resolve.work);

- mutex_lock(&server->srv_mutex);
+ cifs_server_lock(server);

/*
* Resolve the hostname again to make sure that IP address is up-to-date.
@@ -159,7 +159,7 @@ static void cifs_resolve_server(struct work_struct *work)
__func__, rc);
}

- mutex_unlock(&server->srv_mutex);
+ cifs_server_unlock(server);
}

/*
@@ -267,7 +267,7 @@ cifs_abort_connection(struct TCP_Server_Info *server)

/* do not want to be sending data on a socket we are freeing */
cifs_dbg(FYI, "%s: tearing down socket\n", __func__);
- mutex_lock(&server->srv_mutex);
+ cifs_server_lock(server);
if (server->ssocket) {
cifs_dbg(FYI, "State: 0x%x Flags: 0x%lx\n", server->ssocket->state,
server->ssocket->flags);
@@ -296,7 +296,7 @@ cifs_abort_connection(struct TCP_Server_Info *server)
mid->mid_flags |= MID_DELETED;
}
spin_unlock(&GlobalMid_Lock);
- mutex_unlock(&server->srv_mutex);
+ cifs_server_unlock(server);

cifs_dbg(FYI, "%s: issuing mid callbacks\n", __func__);
list_for_each_entry_safe(mid, nmid, &retry_list, qhead) {
@@ -306,9 +306,9 @@ cifs_abort_connection(struct TCP_Server_Info *server)
}

if (cifs_rdma_enabled(server)) {
- mutex_lock(&server->srv_mutex);
+ cifs_server_lock(server);
smbd_destroy(server);
- mutex_unlock(&server->srv_mutex);
+ cifs_server_unlock(server);
}
}

@@ -359,7 +359,7 @@ static int __cifs_reconnect(struct TCP_Server_Info *server,

do {
try_to_freeze();
- mutex_lock(&server->srv_mutex);
+ cifs_server_lock(server);

if (!cifs_swn_set_server_dstaddr(server)) {
/* resolve the hostname again to make sure that IP address is up-to-date */
@@ -372,7 +372,7 @@ static int __cifs_reconnect(struct TCP_Server_Info *server,
else
rc = generic_ip_connect(server);
if (rc) {
- mutex_unlock(&server->srv_mutex);
+ cifs_server_unlock(server);
cifs_dbg(FYI, "%s: reconnect error %d\n", __func__, rc);
msleep(3000);
} else {
@@ -383,7 +383,7 @@ static int __cifs_reconnect(struct TCP_Server_Info *server,
server->tcpStatus = CifsNeedNegotiate;
spin_unlock(&cifs_tcp_ses_lock);
cifs_swn_reset_server_dstaddr(server);
- mutex_unlock(&server->srv_mutex);
+ cifs_server_unlock(server);
mod_delayed_work(cifsiod_wq, &server->reconnect, 0);
}
} while (server->tcpStatus == CifsNeedReconnect);
@@ -488,12 +488,12 @@ static int reconnect_dfs_server(struct TCP_Server_Info *server)

do {
try_to_freeze();
- mutex_lock(&server->srv_mutex);
+ cifs_server_lock(server);

rc = reconnect_target_unlocked(server, &tl, &target_hint);
if (rc) {
/* Failed to reconnect socket */
- mutex_unlock(&server->srv_mutex);
+ cifs_server_unlock(server);
cifs_dbg(FYI, "%s: reconnect error %d\n", __func__, rc);
msleep(3000);
continue;
@@ -510,7 +510,7 @@ static int reconnect_dfs_server(struct TCP_Server_Info *server)
server->tcpStatus = CifsNeedNegotiate;
spin_unlock(&cifs_tcp_ses_lock);
cifs_swn_reset_server_dstaddr(server);
- mutex_unlock(&server->srv_mutex);
+ cifs_server_unlock(server);
mod_delayed_work(cifsiod_wq, &server->reconnect, 0);
} while (server->tcpStatus == CifsNeedReconnect);

@@ -1565,7 +1565,7 @@ cifs_get_tcp_session(struct smb3_fs_context *ctx,
init_waitqueue_head(&tcp_ses->response_q);
init_waitqueue_head(&tcp_ses->request_q);
INIT_LIST_HEAD(&tcp_ses->pending_mid_q);
- mutex_init(&tcp_ses->srv_mutex);
+ mutex_init(&tcp_ses->_srv_mutex);
memcpy(tcp_ses->workstation_RFC1001_name,
ctx->source_rfc1001_name, RFC1001_NAME_LEN_WITH_NULL);
memcpy(tcp_ses->server_RFC1001_name,
diff --git a/fs/cifs/dfs_cache.c b/fs/cifs/dfs_cache.c
index 956f8e5cf3e7..261ebe88a328 100644
--- a/fs/cifs/dfs_cache.c
+++ b/fs/cifs/dfs_cache.c
@@ -1327,9 +1327,9 @@ static bool target_share_equal(struct TCP_Server_Info *server, const char *s1, c
cifs_dbg(VFS, "%s: failed to convert address \'%s\'. skip address matching.\n",
__func__, ip);
} else {
- mutex_lock(&server->srv_mutex);
+ cifs_server_lock(server);
match = cifs_match_ipaddr((struct sockaddr *)&server->dstaddr, &sa);
- mutex_unlock(&server->srv_mutex);
+ cifs_server_unlock(server);
}

kfree(ip);
diff --git a/fs/cifs/sess.c b/fs/cifs/sess.c
index 32f478c7a66d..dadfc3c6ba60 100644
--- a/fs/cifs/sess.c
+++ b/fs/cifs/sess.c
@@ -1093,14 +1093,14 @@ sess_establish_session(struct sess_data *sess_data)
struct cifs_ses *ses = sess_data->ses;
struct TCP_Server_Info *server = sess_data->server;

- mutex_lock(&server->srv_mutex);
+ cifs_server_lock(server);
if (!server->session_estab) {
if (server->sign) {
server->session_key.response =
kmemdup(ses->auth_key.response,
ses->auth_key.len, GFP_KERNEL);
if (!server->session_key.response) {
- mutex_unlock(&server->srv_mutex);
+ cifs_server_unlock(server);
return -ENOMEM;
}
server->session_key.len =
@@ -1109,7 +1109,7 @@ sess_establish_session(struct sess_data *sess_data)
server->sequence_number = 0x2;
server->session_estab = true;
}
- mutex_unlock(&server->srv_mutex);
+ cifs_server_unlock(server);

cifs_dbg(FYI, "CIFS session established successfully\n");
return 0;
diff --git a/fs/cifs/smb1ops.c b/fs/cifs/smb1ops.c
index c71c9a44bef4..2e20ee4dab7b 100644
--- a/fs/cifs/smb1ops.c
+++ b/fs/cifs/smb1ops.c
@@ -38,10 +38,10 @@ send_nt_cancel(struct TCP_Server_Info *server, struct smb_rqst *rqst,
in_buf->WordCount = 0;
put_bcc(0, in_buf);

- mutex_lock(&server->srv_mutex);
+ cifs_server_lock(server);
rc = cifs_sign_smb(in_buf, server, &mid->sequence_number);
if (rc) {
- mutex_unlock(&server->srv_mutex);
+ cifs_server_unlock(server);
return rc;
}

@@ -55,7 +55,7 @@ send_nt_cancel(struct TCP_Server_Info *server, struct smb_rqst *rqst,
if (rc < 0)
server->sequence_number--;

- mutex_unlock(&server->srv_mutex);
+ cifs_server_unlock(server);

cifs_dbg(FYI, "issued NT_CANCEL for mid %u, rc = %d\n",
get_mid(in_buf), rc);
diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
index 1b7ad0c09566..2397bcf22235 100644
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -1369,13 +1369,13 @@ SMB2_sess_establish_session(struct SMB2_sess_data *sess_data)
struct cifs_ses *ses = sess_data->ses;
struct TCP_Server_Info *server = sess_data->server;

- mutex_lock(&server->srv_mutex);
+ cifs_server_lock(server);
if (server->ops->generate_signingkey) {
rc = server->ops->generate_signingkey(ses, server);
if (rc) {
cifs_dbg(FYI,
"SMB3 session key generation failed\n");
- mutex_unlock(&server->srv_mutex);
+ cifs_server_unlock(server);
return rc;
}
}
@@ -1383,7 +1383,7 @@ SMB2_sess_establish_session(struct SMB2_sess_data *sess_data)
server->sequence_number = 0x2;
server->session_estab = true;
}
- mutex_unlock(&server->srv_mutex);
+ cifs_server_unlock(server);

cifs_dbg(FYI, "SMB2/3 session established successfully\n");
return rc;
diff --git a/fs/cifs/smbdirect.c b/fs/cifs/smbdirect.c
index 31ef64eb7fbb..35829d2a0918 100644
--- a/fs/cifs/smbdirect.c
+++ b/fs/cifs/smbdirect.c
@@ -1382,9 +1382,9 @@ void smbd_destroy(struct TCP_Server_Info *server)
log_rdma_event(INFO, "freeing mr list\n");
wake_up_interruptible_all(&info->wait_mr);
while (atomic_read(&info->mr_used_count)) {
- mutex_unlock(&server->srv_mutex);
+ cifs_server_unlock(server);
msleep(1000);
- mutex_lock(&server->srv_mutex);
+ cifs_server_lock(server);
}
destroy_mr_list(info);

diff --git a/fs/cifs/transport.c b/fs/cifs/transport.c
index c667e6ddfe2f..71750cf7bf55 100644
--- a/fs/cifs/transport.c
+++ b/fs/cifs/transport.c
@@ -822,7 +822,7 @@ cifs_call_async(struct TCP_Server_Info *server, struct smb_rqst *rqst,
} else
instance = exist_credits->instance;

- mutex_lock(&server->srv_mutex);
+ cifs_server_lock(server);

/*
* We can't use credits obtained from the previous session to send this
@@ -830,14 +830,14 @@ cifs_call_async(struct TCP_Server_Info *server, struct smb_rqst *rqst,
* return -EAGAIN in such cases to let callers handle it.
*/
if (instance != server->reconnect_instance) {
- mutex_unlock(&server->srv_mutex);
+ cifs_server_unlock(server);
add_credits_and_wake_if(server, &credits, optype);
return -EAGAIN;
}

mid = server->ops->setup_async_request(server, rqst);
if (IS_ERR(mid)) {
- mutex_unlock(&server->srv_mutex);
+ cifs_server_unlock(server);
add_credits_and_wake_if(server, &credits, optype);
return PTR_ERR(mid);
}
@@ -868,7 +868,7 @@ cifs_call_async(struct TCP_Server_Info *server, struct smb_rqst *rqst,
cifs_delete_mid(mid);
}

- mutex_unlock(&server->srv_mutex);
+ cifs_server_unlock(server);

if (rc == 0)
return 0;
@@ -1109,7 +1109,7 @@ compound_send_recv(const unsigned int xid, struct cifs_ses *ses,
* of smb data.
*/

- mutex_lock(&server->srv_mutex);
+ cifs_server_lock(server);

/*
* All the parts of the compound chain belong obtained credits from the
@@ -1119,7 +1119,7 @@ compound_send_recv(const unsigned int xid, struct cifs_ses *ses,
* handle it.
*/
if (instance != server->reconnect_instance) {
- mutex_unlock(&server->srv_mutex);
+ cifs_server_unlock(server);
for (j = 0; j < num_rqst; j++)
add_credits(server, &credits[j], optype);
return -EAGAIN;
@@ -1131,7 +1131,7 @@ compound_send_recv(const unsigned int xid, struct cifs_ses *ses,
revert_current_mid(server, i);
for (j = 0; j < i; j++)
cifs_delete_mid(midQ[j]);
- mutex_unlock(&server->srv_mutex);
+ cifs_server_unlock(server);

/* Update # of requests on wire to server */
for (j = 0; j < num_rqst; j++)
@@ -1163,7 +1163,7 @@ compound_send_recv(const unsigned int xid, struct cifs_ses *ses,
server->sequence_number -= 2;
}

- mutex_unlock(&server->srv_mutex);
+ cifs_server_unlock(server);

/*
* If sending failed for some reason or it is an oplock break that we
@@ -1190,9 +1190,9 @@ compound_send_recv(const unsigned int xid, struct cifs_ses *ses,
if ((ses->status == CifsNew) || (optype & CIFS_NEG_OP) || (optype & CIFS_SESS_OP)) {
spin_unlock(&cifs_tcp_ses_lock);

- mutex_lock(&server->srv_mutex);
+ cifs_server_lock(server);
smb311_update_preauth_hash(ses, server, rqst[0].rq_iov, rqst[0].rq_nvec);
- mutex_unlock(&server->srv_mutex);
+ cifs_server_unlock(server);

spin_lock(&cifs_tcp_ses_lock);
}
@@ -1266,9 +1266,9 @@ compound_send_recv(const unsigned int xid, struct cifs_ses *ses,
.iov_len = resp_iov[0].iov_len
};
spin_unlock(&cifs_tcp_ses_lock);
- mutex_lock(&server->srv_mutex);
+ cifs_server_lock(server);
smb311_update_preauth_hash(ses, server, &iov, 1);
- mutex_unlock(&server->srv_mutex);
+ cifs_server_unlock(server);
spin_lock(&cifs_tcp_ses_lock);
}
spin_unlock(&cifs_tcp_ses_lock);
@@ -1385,11 +1385,11 @@ SendReceive(const unsigned int xid, struct cifs_ses *ses,
and avoid races inside tcp sendmsg code that could cause corruption
of smb data */

- mutex_lock(&server->srv_mutex);
+ cifs_server_lock(server);

rc = allocate_mid(ses, in_buf, &midQ);
if (rc) {
- mutex_unlock(&server->srv_mutex);
+ cifs_server_unlock(server);
/* Update # of requests on wire to server */
add_credits(server, &credits, 0);
return rc;
@@ -1397,7 +1397,7 @@ SendReceive(const unsigned int xid, struct cifs_ses *ses,

rc = cifs_sign_smb(in_buf, server, &midQ->sequence_number);
if (rc) {
- mutex_unlock(&server->srv_mutex);
+ cifs_server_unlock(server);
goto out;
}

@@ -1411,7 +1411,7 @@ SendReceive(const unsigned int xid, struct cifs_ses *ses,
if (rc < 0)
server->sequence_number -= 2;

- mutex_unlock(&server->srv_mutex);
+ cifs_server_unlock(server);

if (rc < 0)
goto out;
@@ -1530,18 +1530,18 @@ SendReceiveBlockingLock(const unsigned int xid, struct cifs_tcon *tcon,
and avoid races inside tcp sendmsg code that could cause corruption
of smb data */

- mutex_lock(&server->srv_mutex);
+ cifs_server_lock(server);

rc = allocate_mid(ses, in_buf, &midQ);
if (rc) {
- mutex_unlock(&server->srv_mutex);
+ cifs_server_unlock(server);
return rc;
}

rc = cifs_sign_smb(in_buf, server, &midQ->sequence_number);
if (rc) {
cifs_delete_mid(midQ);
- mutex_unlock(&server->srv_mutex);
+ cifs_server_unlock(server);
return rc;
}

@@ -1554,7 +1554,7 @@ SendReceiveBlockingLock(const unsigned int xid, struct cifs_tcon *tcon,
if (rc < 0)
server->sequence_number -= 2;

- mutex_unlock(&server->srv_mutex);
+ cifs_server_unlock(server);

if (rc < 0) {
cifs_delete_mid(midQ);
--
2.35.1