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CIFS: Check for reconnects before sending compound requests 

The reconnect might have happended after we obtained credits
and before we acquired srv_mutex. Check for that under the mutex
and retry a sync operation if the reconnect is detected.

Signed-off-by: Pavel Shilovsky <pshilov@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
hifive-unleashed-5.1
Pavel Shilovsky 2019-01-15 16:07:52 -08:00 committed by Steve French
parent 3349c3a79f
commit 97ea499883
1 changed files with 36 additions and 2 deletions
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38
fs/cifs/transport.c
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@ -843,6 +843,7 @@ compound_send_recv(const unsigned int xid, struct cifs_ses *ses,
{ .value = 0, .instance = 0 }
};
unsigned int instance;
unsigned int first_instance = 0;
char *buf;
timeout = flags & CIFS_TIMEOUT_MASK;
@ -870,6 +871,25 @@ compound_send_recv(const unsigned int xid, struct cifs_ses *ses,
for (i = 0; i < num_rqst; i++) {
rc = wait_for_free_request(ses->server, timeout, optype,
&instance);
if (rc == 0) {
credits[i].value = 1;
credits[i].instance = instance;
/*
* All parts of the compound chain must get credits from
* the same session, otherwise we may end up using more
* credits than the server granted. If there were
* reconnects in between, return -EAGAIN and let callers
* handle it.
*/
if (i == 0)
first_instance = instance;
else if (first_instance != instance) {
i++;
rc = -EAGAIN;
}
}
if (rc) {
/*
* We haven't sent an SMB packet to the server yet but
@ -884,8 +904,6 @@ compound_send_recv(const unsigned int xid, struct cifs_ses *ses,
add_credits(ses->server, &credits[j], optype);
return rc;
}
credits[i].value = 1;
credits[i].instance = instance;
}
/*
@ -896,6 +914,22 @@ compound_send_recv(const unsigned int xid, struct cifs_ses *ses,
mutex_lock(&ses->server->srv_mutex);
/*
* All the parts of the compound chain belong obtained credits from the
* same session (see the appropriate checks above). In the same time
* there might be reconnects after those checks but before we acquired
* the srv_mutex. We can not use credits obtained from the previous
* session to send this request. Check if there were reconnects after
* we obtained credits and return -EAGAIN in such cases to let callers
* handle it.
*/
if (first_instance != ses->server->reconnect_instance) {
mutex_unlock(&ses->server->srv_mutex);
for (j = 0; j < num_rqst; j++)
add_credits(ses->server, &credits[j], optype);
return -EAGAIN;
}
for (i = 0; i < num_rqst; i++) {
midQ[i] = ses->server->ops->setup_request(ses, &rqst[i]);
if (IS_ERR(midQ[i])) {