From 254174b8e94c063f8d15bb86f5b55ac123a7953c Mon Sep 17 00:00:00 2001
From: Bill Zissimopoulos <billziss@navimatics.com>
Date: Mon, 4 Nov 2019 16:30:30 -0800
Subject: [PATCH] sys: avoid using FspFsextProvider unnecessarily

---
 src/sys/device.c | 16 +++++-----------
 src/sys/driver.h |  1 +
 src/sys/fsext.c  | 16 +---------------
 src/sys/volume.c |  9 ++++-----
 4 files changed, 11 insertions(+), 31 deletions(-)

diff --git a/src/sys/device.c b/src/sys/device.c
index 952187e6..859822f6 100644
--- a/src/sys/device.c
+++ b/src/sys/device.c
@@ -340,6 +340,7 @@ static NTSTATUS FspFsvolDeviceInit(PDEVICE_OBJECT DeviceObject)
             Result = Provider->DeviceInit(DeviceObject, &FsvolDeviceExtension->VolumeParams);
             if (!NT_SUCCESS(Result))
                 return Result;
+            FsvolDeviceExtension->Provider = Provider;
             FsvolDeviceExtension->InitDoneFsext = 1;
         }
         else
@@ -525,10 +526,8 @@ static VOID FspFsvolDeviceFini(PDEVICE_OBJECT DeviceObject)
     /* finalize any fsext provider */
     if (FsvolDeviceExtension->InitDoneFsext)
     {
-        FSP_FSEXT_PROVIDER *Provider = FspFsextProvider(
-            FsvolDeviceExtension->VolumeParams.FsextControlCode, 0);
-        if (0 != Provider)
-            Provider->DeviceFini(DeviceObject);
+        if (0 != FsvolDeviceExtension->Provider)
+            FsvolDeviceExtension->Provider->DeviceFini(DeviceObject);
     }
 }
 
@@ -577,13 +576,8 @@ static VOID FspFsvolDeviceExpirationRoutine(PVOID Context)
     FspMetaCacheInvalidateExpired(FsvolDeviceExtension->DirInfoCache, InterruptTime);
     FspMetaCacheInvalidateExpired(FsvolDeviceExtension->StreamInfoCache, InterruptTime);
     /* run any fsext provider expiration routine */
-    if (0 != FsvolDeviceExtension->VolumeParams.FsextControlCode)
-    {
-        FSP_FSEXT_PROVIDER *Provider = FspFsextProvider(
-            FsvolDeviceExtension->VolumeParams.FsextControlCode, 0);
-        if (0 != Provider)
-            Provider->DeviceExpirationRoutine(DeviceObject, InterruptTime);
-    }
+    if (0 != FsvolDeviceExtension->Provider)
+        FsvolDeviceExtension->Provider->DeviceExpirationRoutine(DeviceObject, InterruptTime);
     FspIoqRemoveExpired(FsvolDeviceExtension->Ioq, InterruptTime);
 
     KeAcquireSpinLock(&FsvolDeviceExtension->ExpirationLock, &Irql);
diff --git a/src/sys/driver.h b/src/sys/driver.h
index 787c87d8..c04e9858 100644
--- a/src/sys/driver.h
+++ b/src/sys/driver.h
@@ -1079,6 +1079,7 @@ typedef struct
     PVPB SwapVpb;
     FSP_DELAYED_WORK_ITEM DeleteVolumeDelayedWorkItem;
     FSP_FSCTL_VOLUME_PARAMS VolumeParams;
+    FSP_FSEXT_PROVIDER *Provider;
     UNICODE_STRING VolumePrefix;
     UNICODE_PREFIX_TABLE_ENTRY VolumePrefixEntry;
     FSP_IOQ *Ioq;
diff --git a/src/sys/fsext.c b/src/sys/fsext.c
index 0be629c4..e4faacb0 100644
--- a/src/sys/fsext.c
+++ b/src/sys/fsext.c
@@ -28,7 +28,7 @@
  * the data structure used to store providers (currently 2 parallel
  * arrays) must be revisited.
  */
-#define FSP_FSEXT_PROVIDER_COUNTMAX     4
+#define FSP_FSEXT_PROVIDER_COUNTMAX     16
 
 static KSPIN_LOCK FsextSpinLock = 0;
 static UINT32 FsextControlCodes[FSP_FSEXT_PROVIDER_COUNTMAX];
@@ -37,23 +37,9 @@ static FSP_FSEXT_PROVIDER *FsextProviders[FSP_FSEXT_PROVIDER_COUNTMAX];
 static inline
 FSP_FSEXT_PROVIDER *FspFsextProviderGet(UINT32 FsextControlCode)
 {
-#if 0
     for (ULONG I = 0; FSP_FSEXT_PROVIDER_COUNTMAX > I; I++)
         if (FsextControlCode == FsextControlCodes[I])
             return FsextProviders[I];
-#else
-    /* unroll by hand */
-    FSP_FSCTL_STATIC_ASSERT(4 == FSP_FSEXT_PROVIDER_COUNTMAX,
-        "unrolled loop expects FsextProviders to have 4 elements");
-    if (FsextControlCode == FsextControlCodes[0])
-        return FsextProviders[0];
-    if (FsextControlCode == FsextControlCodes[1])
-        return FsextProviders[1];
-    if (FsextControlCode == FsextControlCodes[2])
-        return FsextProviders[2];
-    if (FsextControlCode == FsextControlCodes[3])
-        return FsextProviders[3];
-#endif
 
     return 0;
 }
diff --git a/src/sys/volume.c b/src/sys/volume.c
index 3292d35c..bf78785f 100644
--- a/src/sys/volume.c
+++ b/src/sys/volume.c
@@ -992,14 +992,13 @@ NTSTATUS FspVolumeTransactFsext(
     if (!FspDeviceReference(FsvolDeviceObject))
         return STATUS_CANCELLED;
 
+    FSP_FSVOL_DEVICE_EXTENSION *FsvolDeviceExtension = FspFsvolDeviceExtension(FsvolDeviceObject);
     NTSTATUS Result = STATUS_INVALID_DEVICE_REQUEST;
     if (IrpSp->Parameters.FileSystemControl.FsControlCode ==
-        FspFsvolDeviceExtension(FsvolDeviceObject)->VolumeParams.FsextControlCode)
+        FsvolDeviceExtension->VolumeParams.FsextControlCode)
     {
-        FSP_FSEXT_PROVIDER *Provider = FspFsextProvider(
-            IrpSp->Parameters.FileSystemControl.FsControlCode, 0);
-        if (0 != Provider)
-            Result = Provider->DeviceTransact(FsvolDeviceObject, Irp);
+        if (0 != FsvolDeviceExtension->Provider)
+            Result = FsvolDeviceExtension->Provider->DeviceTransact(FsvolDeviceObject, Irp);
     }
 
     FspDeviceDereference(FsvolDeviceObject);