[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>

1 files changed, 24 insertions, 12 deletions

diff --git a/drivers/s390/char/vmlogrdr.c b/drivers/s390/char/vmlogrdr.c
index 9f661426e4a1..1cc726b98ec8 100644
--- 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;
 }