[PATCH 1/3] XenDisk: Report Discard support by issuing an Inquiry

[Owen Smith <owen.smith@xxxxxxxxxx>]

From: Owen Smith <owen.smith@xxxxxxxxx>

When XenDisk starts, issue an inquiry to determine the status of discard
support in the backend. If the backend exposes discard support, allow
XenDisk to respond to the appropriate property requests, and forward the
trim requests to XenVbd.

Signed-off-by: Owen Smith <owen.smith@xxxxxxxxxx>
---
 src/xendisk/pdo.c | 88 ++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 84 insertions(+), 4 deletions(-)

diff --git a/src/xendisk/pdo.c b/src/xendisk/pdo.c
index f714efb..5d40a13 100644
--- a/src/xendisk/pdo.c
+++ b/src/xendisk/pdo.c
@@ -63,6 +63,7 @@ struct _XENDISK_PDO {
     PXENDISK_FDO                Fdo;
 
     BOOLEAN                     InterceptTrim;
+    BOOLEAN                     DiscardSupported;
     ULONG                       SectorSize;
     ULONG                       PhysSectorSize;
 };
@@ -519,6 +520,72 @@ fail1:
     return status;
 }
 
+static NTSTATUS
+PdoSendInquiryB0Synchronous(
+    IN  PXENDISK_PDO        Pdo,
+    OUT PBOOLEAN            Supported
+    )
+{
+    SCSI_REQUEST_BLOCK      Srb;
+    PCDB                    Cdb;
+    PVPD_BLOCK_LIMITS_PAGE  BlockLimits;
+    ULONG                   Length;
+    NTSTATUS                status;
+
+    Trace("====>\n");
+
+    Length = sizeof(VPD_BLOCK_LIMITS_PAGE);
+    *Supported = FALSE;
+
+    status = STATUS_NO_MEMORY;
+    BlockLimits = __PdoAllocate(Length);
+    if (BlockLimits == NULL)
+        goto fail1;
+
+    RtlZeroMemory(&Srb, sizeof(SCSI_REQUEST_BLOCK));
+    Srb.Length = sizeof(SCSI_REQUEST_BLOCK);
+    Srb.SrbFlags = 0;
+    Srb.Function = SRB_FUNCTION_EXECUTE_SCSI;
+    Srb.DataBuffer = BlockLimits;
+    Srb.DataTransferLength = Length;
+    Srb.TimeOutValue = (ULONG)-1;
+    Srb.CdbLength = 6;
+
+    Cdb = (PCDB)&Srb.Cdb[0];
+    Cdb->CDB6INQUIRY3.OperationCode = SCSIOP_INQUIRY;
+    Cdb->CDB6INQUIRY3.PageCode = 0xB0;
+    Cdb->CDB6INQUIRY3.EnableVitalProductData = 1;
+    Cdb->CDB6INQUIRY3.AllocationLength = (UCHAR)Length;
+
+    status = PdoSendAwaitSrb(Pdo, &Srb);
+    if (!NT_SUCCESS(status))
+        goto fail2;
+
+    status = STATUS_UNSUCCESSFUL;
+    if (Srb.DataTransferLength < Length)
+        goto fail3;
+
+    *Supported = BlockLimits->UGAValid;
+
+    __PdoFree(BlockLimits);
+
+    Trace("<====\n");
+    return STATUS_SUCCESS;
+
+fail3:
+    Error("fail3\n");
+
+fail2:
+    Error("fail2\n");
+
+    __PdoFree(BlockLimits);
+
+fail1:
+    Error("fail1 (%08x)\n", status);
+
+    return status;
+}
+
 static NTSTATUS
 PdoSendTrimSynchronous(
     IN  PXENDISK_PDO            Pdo,
@@ -674,7 +741,7 @@ PdoQueryProperty(
 
     switch (Query->PropertyId) {
     case StorageDeviceTrimProperty:
-        if (!Pdo->InterceptTrim) {
+        if (!Pdo->InterceptTrim || !Pdo->DiscardSupported) {
             status = PdoForwardIrpAndForget(Pdo, Irp);
             break;
         }
@@ -753,7 +820,7 @@ PdoManageDataSetAttributes(
 
     switch (Attributes->Action) {
     case DeviceDsmAction_Trim:
-        if (!Pdo->InterceptTrim) {
+        if (!Pdo->InterceptTrim || !Pdo->DiscardSupported) {
             status = PdoForwardIrpAndForget(Pdo, Irp);
             break;
         }
@@ -830,6 +897,7 @@ PdoStartDevice(
     ULONG               PhysSectorSize;
     ULONG64             SectorCount;
     ULONG64             Size;
+    BOOLEAN             DiscardSupported;
     POWER_STATE         PowerState;
     NTSTATUS            status;
 
@@ -848,14 +916,22 @@ PdoStartDevice(
     if (!NT_SUCCESS(status))
         goto fail3;
 
+    status = PdoSendInquiryB0Synchronous(Pdo,
+                                         &DiscardSupported);
+    if (!NT_SUCCESS(status))
+        goto fail4;
+
     Pdo->SectorSize = SectorSize;
     Pdo->PhysSectorSize = PhysSectorSize;
+    Pdo->DiscardSupported = DiscardSupported;
 
     Size = SectorSize * SectorCount;
     Size >>= 20; // Scale to megabytes
 
-    Verbose("%s: %luMB (%uB sectors)\n",
-            __PdoGetName(Pdo), Size, SectorSize);
+    Verbose("%s: %luMB (%uB sectors)%s%s\n",
+            __PdoGetName(Pdo), Size, SectorSize,
+            Pdo->DiscardSupported ? " DISCARD" : "",
+            Pdo->InterceptTrim ? "" : " (VETOED)");
 
     __PdoSetSystemPowerState(Pdo, PowerSystemWorking);
     __PdoSetDevicePowerState(Pdo, PowerDeviceD0);
@@ -874,6 +950,9 @@ PdoStartDevice(
 
     return STATUS_SUCCESS;
 
+fail4:
+    Error("fail4\n");
+
 fail3:
     Error("fail3\n");
 
@@ -1904,6 +1983,7 @@ PdoDestroy(
     Dx->Pdo = NULL;
 
     Pdo->InterceptTrim = FALSE;
+    Pdo->DiscardSupported = FALSE;
 
     RtlZeroMemory(Pdo->Name, sizeof (Pdo->Name));
 
-- 
2.51.2.windows.1