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@xxxxxxxxxxxxx>
---
fs/cifs/transport.c | 38 ++++++++++++++++++++++++++++++++++++--
1 file changed, 36 insertions(+), 2 deletions(-)
diff --git a/fs/cifs/transport.c b/fs/cifs/transport.c
index 26e9912..2187bc3 100644
--- a/fs/cifs/transport.c
+++ b/fs/cifs/transport.c
@@ -869,6 +869,7 @@ 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;
@@ -896,6 +897,25 @@ 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
@@ -910,8 +930,6 @@ 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;
}
/*
@@ -922,6 +940,22 @@ 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])) {
--
2.7.4
