[win-pv-devel] [PATCH 3/4] Remove FreshSrbs queue

[<owen.smith@xxxxxxxxxx>]

From: Owen Smith <owen.smith@xxxxxxxxxx>

Any SRB that fails to prepare will be completed with SRB_STATUS_BUSY,
so that storport can manage the queue. SRBs are prepared in the StartIo
handler, and appended to the PreparedReqs queue. All possible PreparedReqs
are submitted, and if there is more PreparedReqs, the DPC is triggered to
submit more when possible.

Signed-off-by: Owen Smith <owen.smith@xxxxxxxxxx>
---
 src/xenvbd/ring.c | 112 +++++++++++-------------------------------------------
 1 file changed, 23 insertions(+), 89 deletions(-)

diff --git a/src/xenvbd/ring.c b/src/xenvbd/ring.c
index e569dbd..ef94513 100644
--- a/src/xenvbd/ring.c
+++ b/src/xenvbd/ring.c
@@ -80,7 +80,6 @@ struct _XENVBD_RING {
     PXENBUS_CACHE                   RequestCache;
     PXENBUS_CACHE                   SegmentCache;
     PXENBUS_CACHE                   IndirectCache;
-    XENVBD_QUEUE                    FreshSrbs;
     XENVBD_QUEUE                    PreparedReqs;
     XENVBD_QUEUE                    SubmittedReqs;
     XENVBD_QUEUE                    ShutdownSrbs;
@@ -936,40 +935,26 @@ fail1:
 }
 
 static FORCEINLINE BOOLEAN
-RingPrepareFresh(
-    IN  PXENVBD_RING    Ring
+RingPrepareRequest(
+    IN  PXENVBD_RING    Ring,
+    IN  PXENVBD_SRBEXT  SrbExt
     )
 {
-    PXENVBD_SRBEXT      SrbExt;
-    PLIST_ENTRY         ListEntry;
-
-    ListEntry = QueuePop(&Ring->FreshSrbs);
-    if (ListEntry == NULL)
-        return FALSE;   // fresh queue is empty
-
-    SrbExt = CONTAINING_RECORD(ListEntry, XENVBD_SRBEXT, ListEntry);
-
     switch (Cdb_OperationEx(SrbExt->Srb)) {
     case SCSIOP_READ:
     case SCSIOP_WRITE:
-        if (RingPrepareReadWrite(Ring, SrbExt))
-            return TRUE;    // prepared this SRB
-        break;
+        return RingPrepareReadWrite(Ring, SrbExt);
+
     case SCSIOP_SYNCHRONIZE_CACHE:
-        if (RingPrepareSyncCache(Ring, SrbExt))
-            return TRUE;    // prepared this SRB
-        break;
+        return RingPrepareSyncCache(Ring, SrbExt);
+
     case SCSIOP_UNMAP:
-        if (RingPrepareUnmap(Ring, SrbExt))
-            return TRUE;    // prepared this SRB
-        break;
+        return RingPrepareUnmap(Ring, SrbExt);
+
     default:
         ASSERT(FALSE);
-        break;
+        return FALSE;
     }
-    QueueUnPop(&Ring->FreshSrbs, &SrbExt->ListEntry);
-
-    return FALSE;       // prepare failed
 }
 
 static BOOLEAN
@@ -1009,7 +994,7 @@ RingSubmit(
 }
 
 static FORCEINLINE BOOLEAN
-RingSubmitPrepared(
+RingSubmitRequests(
     IN  PXENVBD_RING    Ring
     )
 {
@@ -1039,10 +1024,10 @@ RingSubmitPrepared(
 
         QueueRemove(&Ring->SubmittedReqs, &Request->ListEntry);
         QueueUnPop(&Ring->PreparedReqs, &Request->ListEntry);
-        return FALSE;   // ring full
+        break;
     }
 
-    return TRUE;
+    return QueueCount(&Ring->PreparedReqs) != 0;
 }
 
 static FORCEINLINE VOID
@@ -1056,8 +1041,7 @@ RingCompleteShutdown(
     if (QueueCount(&Ring->ShutdownSrbs) == 0)
         return;
 
-    if (QueueCount(&Ring->FreshSrbs) ||
-        QueueCount(&Ring->PreparedReqs) ||
+    if (QueueCount(&Ring->PreparedReqs) ||
         QueueCount(&Ring->SubmittedReqs))
         return;
 
@@ -1079,38 +1063,6 @@ RingCompleteShutdown(
     }
 }
 
-static BOOLEAN
-RingSubmitRequests(
-    IN  PXENVBD_RING    Ring
-    )
-{
-    BOOLEAN             Retry = FALSE;
-
-    for (;;) {
-        // submit all prepared requests (0 or more requests)
-        // return TRUE if submitted 0 or more requests from prepared queue
-        // return FALSE iff ring is full
-        if (!RingSubmitPrepared(Ring))
-            break;
-
-        // prepare a single SRB (into 1 or more requests)
-        // return TRUE if prepare succeeded
-        // return FALSE if prepare failed or fresh queue empty
-        if (!RingPrepareFresh(Ring))
-            break;
-
-        // back off, check DPC timeout and try again
-        Retry = TRUE;
-        break;
-    }
-
-    // if no requests/SRBs outstanding, complete any shutdown SRBs
-    if (!Retry)
-        RingCompleteShutdown(Ring);
-
-    return Retry;
-}
-
 static FORCEINLINE PCHAR
 __BlkifOperationName(
     IN  UCHAR   Operation
@@ -1258,6 +1210,7 @@ RingNotifyResponses(
     Retry |= RingPoll(Ring);
     Retry |= RingSubmitRequests(Ring);
 
+    RingCompleteShutdown(Ring);
     return Retry;
 }
 
@@ -1415,9 +1368,6 @@ RingDebugCallback(
                  Ring->SegsGranted,
                  Ring->SegsBounced);
 
-    QueueDebugCallback(&Ring->FreshSrbs,
-                       "Fresh    ",
-                       &Ring->DebugInterface);
     QueueDebugCallback(&Ring->PreparedReqs,
                        "Prepared ",
                        &Ring->DebugInterface);
@@ -1557,7 +1507,6 @@ RingCreate(
     KeInitializeThreadedDpc(&(*Ring)->Dpc, RingDpc, *Ring);
     KeSetImportanceDpc(&(*Ring)->Dpc, MediumHighImportance);
 
-    QueueInit(&(*Ring)->FreshSrbs);
     QueueInit(&(*Ring)->PreparedReqs);
     QueueInit(&(*Ring)->SubmittedReqs);
     QueueInit(&(*Ring)->ShutdownSrbs);
@@ -1661,7 +1610,6 @@ fail2:
     RtlZeroMemory(&(*Ring)->CacheInterface,
                   sizeof (XENBUS_CACHE_INTERFACE));
 
-    RtlZeroMemory(&(*Ring)->FreshSrbs, sizeof(XENVBD_QUEUE));
     RtlZeroMemory(&(*Ring)->PreparedReqs, sizeof(XENVBD_QUEUE));
     RtlZeroMemory(&(*Ring)->SubmittedReqs, sizeof(XENVBD_QUEUE));
     RtlZeroMemory(&(*Ring)->ShutdownSrbs, sizeof(XENVBD_QUEUE));
@@ -1704,7 +1652,6 @@ RingDestroy(
     RtlZeroMemory(&Ring->CacheInterface,
                   sizeof (XENBUS_CACHE_INTERFACE));
 
-    RtlZeroMemory(&Ring->FreshSrbs, sizeof(XENVBD_QUEUE));
     RtlZeroMemory(&Ring->PreparedReqs, sizeof(XENVBD_QUEUE));
     RtlZeroMemory(&Ring->SubmittedReqs, sizeof(XENVBD_QUEUE));
     RtlZeroMemory(&Ring->ShutdownSrbs, sizeof(XENVBD_QUEUE));
@@ -2011,23 +1958,6 @@ RingDisable(
             QueueCount(&Ring->SubmittedReqs),
             Count);
 
-    // Abort Fresh SRBs
-    for (;;) {
-        PXENVBD_SRBEXT      SrbExt;
-        PSCSI_REQUEST_BLOCK Srb;
-        PLIST_ENTRY         ListEntry;
-
-        ListEntry = QueuePop(&Ring->FreshSrbs);
-        if (ListEntry == NULL)
-            break;
-        SrbExt = CONTAINING_RECORD(ListEntry, XENVBD_SRBEXT, ListEntry);
-        Srb = SrbExt->Srb;
-
-        Srb->SrbStatus = SRB_STATUS_ABORTED;
-        Srb->ScsiStatus = 0x40; // SCSI_ABORTED;
-        AdapterCompleteSrb(Adapter, SrbExt);
-    }
-
     // Fail PreparedReqs
     for (;;) {
         PXENVBD_SRBEXT      SrbExt;
@@ -2131,14 +2061,18 @@ RingQueueRequest(
     if (!Ring->Enabled)
         goto fail1;
 
-    QueueAppend(&Ring->FreshSrbs,
-                &SrbExt->ListEntry);
+    if (!RingPrepareRequest(Ring, SrbExt))
+        goto fail2;
 
-    if (KeInsertQueueDpc(&Ring->Dpc, NULL, NULL))
-           ++Ring->Dpcs;
+    if (RingSubmitRequests(Ring)) {
+        // more prepared-reqs to submit
+        if (KeInsertQueueDpc(&Ring->Dpc, NULL, NULL))
+            ++Ring->Dpcs;
+    }
 
     return TRUE;
 
+fail2:
 fail1:
     Srb->SrbStatus = SRB_STATUS_BUSY;
     return FALSE;
-- 
2.8.3


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