[reactos] 49/100: [NTOS:CC] Restore read-ahead behaviour in CcCopyRead

[Jérôme Gardou]

https://git.reactos.org/?p=reactos.git;a=commitdiff;h=a52bc6d1799385726097e…

commit a52bc6d1799385726097ecf701f833b7a327a08e
Author:     Jérôme Gardou <jerome.gardou(a)reactos.org>
AuthorDate: Fri Dec 11 14:31:08 2020 +0100
Commit:     Jérôme Gardou <jerome.gardou(a)reactos.org>
CommitDate: Wed Feb 3 09:41:22 2021 +0100

    [NTOS:CC] Restore read-ahead behaviour in CcCopyRead
---
 ntoskrnl/cc/copy.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/ntoskrnl/cc/copy.c b/ntoskrnl/cc/copy.c
index 315e9f1f1b0..3dd172fa9db 100644
--- a/ntoskrnl/cc/copy.c
+++ b/ntoskrnl/cc/copy.c
@@ -556,6 +556,27 @@ CcCopyRead (
     IoStatus->Status = STATUS_SUCCESS;
     IoStatus->Information = ReadLength;
 
+    /* If that was a successful sync read operation, let's handle read ahead */
+    if (Length == 0 && Wait)
+    {
+        PPRIVATE_CACHE_MAP PrivateCacheMap = FileObject->PrivateCacheMap;
+
+        /* If file isn't random access and next read may get us cross VACB boundary,
+         * schedule next read
+         */
+        if (!BooleanFlagOn(FileObject->Flags, FO_RANDOM_ACCESS) &&
+            (CurrentOffset - 1) / VACB_MAPPING_GRANULARITY != (CurrentOffset + ReadLength
- 1) / VACB_MAPPING_GRANULARITY)
+        {
+            CcScheduleReadAhead(FileObject, FileOffset, ReadLength);
+        }
+
+        /* And update read history in private cache map */
+        PrivateCacheMap->FileOffset1.QuadPart =
PrivateCacheMap->FileOffset2.QuadPart;
+        PrivateCacheMap->BeyondLastByte1.QuadPart =
PrivateCacheMap->BeyondLastByte2.QuadPart;
+        PrivateCacheMap->FileOffset2.QuadPart = FileOffset->QuadPart;
+        PrivateCacheMap->BeyondLastByte2.QuadPart = FileOffset->QuadPart +
ReadLength;
+    }
+
     return TRUE;
 }