From e0b0b1b367f470b5fa1d5e7b0f171485e248823f Mon Sep 17 00:00:00 2001
From: Bill Zissimopoulos <billziss@navimatics.com>
Date: Sat, 22 Oct 2016 14:04:31 -0700
Subject: [PATCH] sys: read,write: IRP_MN_MDL improvements

---
 src/sys/read.c  |  2 --
 src/sys/util.c  | 48 ++++++------------------------------------------
 src/sys/write.c |  2 --
 3 files changed, 6 insertions(+), 46 deletions(-)

diff --git a/src/sys/read.c b/src/sys/read.c
index 405dbbce..1a9f0bd4 100644
--- a/src/sys/read.c
+++ b/src/sys/read.c
@@ -175,8 +175,6 @@ static NTSTATUS FspFsvolReadCached(
     }
     else
     {
-        ASSERT(0 == Irp->MdlAddress);
-
         Result = FspCcMdlRead(FileObject, &ReadOffset, ReadLength, &Irp->MdlAddress,
             &Irp->IoStatus);
         if (!NT_SUCCESS(Result))
diff --git a/src/sys/util.c b/src/sys/util.c
index 9b28cae2..8989b52a 100644
--- a/src/sys/util.c
+++ b/src/sys/util.c
@@ -442,33 +442,15 @@ NTSTATUS FspCcMdlRead(PFILE_OBJECT FileObject, PLARGE_INTEGER FileOffset, ULONG
 {
     PAGED_CODE();
 
-    NTSTATUS Result;
-
-    *PMdlChain = 0;
-
     try
     {
         CcMdlRead(FileObject, FileOffset, Length, PMdlChain, IoStatus);
-        Result = IoStatus->Status;
+        return IoStatus->Status;
     }
-    except(EXCEPTION_EXECUTE_HANDLER)
+    except (EXCEPTION_EXECUTE_HANDLER)
     {
-        Result = GetExceptionCode();
+        return GetExceptionCode();
     }
-
-    if (!NT_SUCCESS(Result))
-    {
-        if (0 != *PMdlChain)
-        {
-            CcMdlReadComplete(FileObject, *PMdlChain);
-            *PMdlChain = 0;
-        }
-
-        IoStatus->Information = 0;
-        IoStatus->Status = Result;
-    }
-
-    return Result;
 }
 
 NTSTATUS FspCcMdlReadComplete(PFILE_OBJECT FileObject, PMDL MdlChain)
@@ -491,33 +473,15 @@ NTSTATUS FspCcPrepareMdlWrite(PFILE_OBJECT FileObject, PLARGE_INTEGER FileOffset
 {
     PAGED_CODE();
 
-    NTSTATUS Result;
-
-    *PMdlChain = 0;
-
     try
     {
         CcPrepareMdlWrite(FileObject, FileOffset, Length, PMdlChain, IoStatus);
-        Result = IoStatus->Status;
+        return IoStatus->Status;
     }
-    except(EXCEPTION_EXECUTE_HANDLER)
+    except (EXCEPTION_EXECUTE_HANDLER)
     {
-        Result = GetExceptionCode();
+        return GetExceptionCode();
     }
-
-    if (!NT_SUCCESS(Result))
-    {
-        if (0 != *PMdlChain)
-        {
-            CcMdlWriteAbort(FileObject, *PMdlChain);
-            *PMdlChain = 0;
-        }
-
-        IoStatus->Information = 0;
-        IoStatus->Status = Result;
-    }
-
-    return Result;
 }
 
 NTSTATUS FspCcMdlWriteComplete(PFILE_OBJECT FileObject, PLARGE_INTEGER FileOffset, PMDL MdlChain)
diff --git a/src/sys/write.c b/src/sys/write.c
index 7f7f851a..550f4a11 100644
--- a/src/sys/write.c
+++ b/src/sys/write.c
@@ -218,8 +218,6 @@ static NTSTATUS FspFsvolWriteCached(
     }
     else
     {
-        ASSERT(0 == Irp->MdlAddress);
-
         Result = FspCcPrepareMdlWrite(FileObject, &WriteOffset, WriteLength, &Irp->MdlAddress,
             &Irp->IoStatus);
         if (!NT_SUCCESS(Result))