[S390] vmlogrdr: purge after recording is switched off

If automatic purge is enabled for a vmlogrdr device, old records are
purged before an IUCV recording service is switched on or off. If z/VM
generates a large number of records between purging and switching the
recording service off, these records remain queued, and may have a
negative performance impact on the z/VM system. To avoid this problem,
we need to purge the records after recording is switched off.

Signed-off-by: Stefan Weinhuber <wein@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

diff --git a/drivers/s390/char/vmlogrdr.c b/drivers/s390/char/vmlogrdr.c
index 9f66142..1cc726b 100644 (file)
--- a/drivers/s390/char/vmlogrdr.c
+++ b/drivers/s390/char/vmlogrdr.c
@@ -249,27 +249,25 @@ static int vmlogrdr_recording(struct vmlogrdr_priv_t * logptr,
        char cp_command[80];
        char cp_response[160];
        char *onoff, *qid_string;
+       int rc;
 
-       memset(cp_command, 0x00, sizeof(cp_command));
-       memset(cp_response, 0x00, sizeof(cp_response));
-
-        onoff = ((action == 1) ? "ON" : "OFF");
+       onoff = ((action == 1) ? "ON" : "OFF");
        qid_string = ((recording_class_AB == 1) ? " QID * " : "");
 
-        /*
+       /*
         * The recording commands needs to be called with option QID
         * for guests that have previlege classes A or B.
         * Purging has to be done as separate step, because recording
         * can't be switched on as long as records are on the queue.
         * Doing both at the same time doesn't work.
         */
-
-       if (purge) {
+       if (purge && (action == 1)) {
+               memset(cp_command, 0x00, sizeof(cp_command));
+               memset(cp_response, 0x00, sizeof(cp_response));
                snprintf(cp_command, sizeof(cp_command),
                         "RECORDING %s PURGE %s",
                         logptr->recording_name,
                         qid_string);
-
                cpcmd(cp_command, cp_response, sizeof(cp_response), NULL);
        }
 
@@ -279,19 +277,33 @@ static int vmlogrdr_recording(struct vmlogrdr_priv_t * logptr,
                logptr->recording_name,
                onoff,
                qid_string);
-
        cpcmd(cp_command, cp_response, sizeof(cp_response), NULL);
        /* The recording command will usually answer with 'Command complete'
         * on success, but when the specific service was never connected
         * before then there might be an additional informational message
         * 'HCPCRC8072I Recording entry not found' before the
-         * 'Command complete'. So I use strstr rather then the strncmp.
+        * 'Command complete'. So I use strstr rather then the strncmp.
         */
        if (strstr(cp_response,"Command complete"))
-               return 0;
+               rc = 0;
        else
-               return -EIO;
+               rc = -EIO;
+       /*
+        * If we turn recording off, we have to purge any remaining records
+        * afterwards, as a large number of queued records may impact z/VM
+        * performance.
+        */
+       if (purge && (action == 0)) {
+               memset(cp_command, 0x00, sizeof(cp_command));
+               memset(cp_response, 0x00, sizeof(cp_response));
+               snprintf(cp_command, sizeof(cp_command),
+                        "RECORDING %s PURGE %s",
+                        logptr->recording_name,
+                        qid_string);
+               cpcmd(cp_command, cp_response, sizeof(cp_response), NULL);
+       }
 
+       return rc;
 }