Kernel - Use the Rtl API to store DokanFCB in a Adelson-Velsky/Landis…

… (AVL) table

Store the DokanFCB in an AVL tree instead of a simple list which becomes slower when there is more context being opened on different files. Moving from O(n) to O(log n).

* The AVL tree is built by using the result of the RtlCompareUnicodeString between the two Fcb FileNames.
* The AVL allocation callback is using a new lookaside list for allocating the AVL Node that contains the Avl Node header and a DokanFCB pointer of the inserted object that is allocated by another lookaside list. This allows us to manage the lifetime of the object outside the Avl table.
* A new log macro was added when VCB is only accessible to limit the compare callback logging to the VCB instance (since we do not have the IRP RequestContext).
* The FCB lookup and insert code were merged as the Avl insert API is doing a lookup to return the matching existing item or the new one inserted.

sys/create.c

@@ -394,7 +394,6 @@ Return Value:
   BOOLEAN eventContextConsumed = FALSE;
   DWORD disposition = 0;
   BOOLEAN fcbLocked = FALSE;
-  BOOLEAN caseInSensitive = TRUE;
   DOKAN_INIT_LOGGER(logger, RequestContext->DeviceObject->DriverObject,
                     IRP_MJ_CREATE);
 
@@ -600,9 +599,6 @@ Return Value:
       __leave;
     }
 
-    caseInSensitive =
-        !(RequestContext->Dcb->MountOptions & DOKAN_EVENT_CASE_SENSITIVE);
-
     // this memory is freed by DokanGetFCB if needed
     // "+ sizeof(WCHAR)" is for the last NULL character
     fileName = DokanAllocZero(fileNameLength + sizeof(WCHAR));
@@ -671,11 +667,9 @@ Return Value:
           fileName = NULL;
           __leave;
         }
-        fcb = DokanGetFCB(RequestContext, parentDir, parentDirLength,
-                          caseInSensitive);
+        fcb = DokanGetFCB(RequestContext, parentDir, parentDirLength);
       } else {
-        fcb = DokanGetFCB(RequestContext, fileName, fileNameLength,
-                          caseInSensitive);
+        fcb = DokanGetFCB(RequestContext, fileName, fileNameLength);
       }
       if (fcb == NULL) {
         status = STATUS_INSUFFICIENT_RESOURCES;

sys/dokan.c

@@ -165,7 +165,7 @@ DokanFilterCallbackAcquireForCreateSection(__in PFS_FILTER_CALLBACK_DATA
 }
 
 BOOLEAN
-DokanLookasideCreate(LOOKASIDE_LIST_EX *pCache, size_t cbElement) {
+DokanLookasideCreate(__in LOOKASIDE_LIST_EX *pCache, __in size_t cbElement) {
   NTSTATUS Status = ExInitializeLookasideListEx(
       pCache, NULL, NULL, NonPagedPool, 0, cbElement, TAG, 0);
 

sys/dokan.h

@@ -366,6 +366,14 @@ typedef struct _DokanVolumeControlBlock {
   PDokanDCB Dcb;
   LIST_ENTRY NextFCB;
 
+  // Avl Table storing the DokanFCB instances.
+  RTL_AVL_TABLE FcbTable;
+  // Lookaside list for the FCB Avl table node containing the Avl header and a
+  // pointer to our DokanFCB that is allocated by the global fcb lookaside list.
+  LOOKASIDE_LIST_EX FCBAvlNodeLookasideList;
+  // Whether the lookaside list was initialized.
+  BOOLEAN FCBAvlNodeLookasideListInit;
+
   // NotifySync is used by notify directory change
   PNOTIFY_SYNC NotifySync;
   LIST_ENTRY DirNotifyList;
@@ -541,6 +549,12 @@ typedef struct _DokanFileControlBlock {
   // owned by the VCB and guarded by the VCB lock.
   BOOLEAN GarbageCollectionGracePeriodPassed;
 
+  // The Fcb was removed from the Avl table and is waiting to be deleted when
+  // all existing handles are being closed. This can happen when a file is
+  // renamed with the destination having an open handle. NTFS denies this action
+  // but due to a Dokan bug, this is actually possible. Until it is fixed, we
+  // reproduce the behavior prior to the Avl table.
+  BOOLEAN ReplacedByRename;
 } DokanFCB, *PDokanFCB;
 
 #define DokanResourceLockRO(resource)                                          \
@@ -1178,6 +1192,9 @@ VOID DokanCreateMountPoint(__in PDokanDCB Dcb);
 VOID FlushFcb(__in PREQUEST_CONTEXT RequestContext, __in PDokanFCB fcb,
               __in_opt PFILE_OBJECT fileObject);
 
+BOOLEAN
+DokanLookasideCreate(__in LOOKASIDE_LIST_EX *pCache, __in size_t cbElement);
+
 PDEVICE_ENTRY
 FindDeviceForDeleteBySessionId(PDOKAN_GLOBAL dokanGlobal, ULONG sessionId);
 

sys/fileinfo.c

@@ -21,6 +21,7 @@ with this program. If not, see <http://www.gnu.org/licenses/>.
 */
 
 #include "dokan.h"
+#include "util/fcb.h"
 #include "util/irp_buffer_helper.h"
 #include "util/str.h"
 
@@ -350,54 +351,51 @@ VOID FlushFcb(__in PREQUEST_CONTEXT RequestContext, __in PDokanFCB Fcb,
   }
 }
 
-VOID FlushAllCachedFcb(__in PREQUEST_CONTEXT RequestContext,
-                       __in PDokanFCB fcbRelatedTo,
-                       __in_opt PFILE_OBJECT fileObject) {
-  PLIST_ENTRY thisEntry, nextEntry, listHead;
-  PDokanFCB fcb = NULL;
+VOID FlushIfDescendant(__in PREQUEST_CONTEXT RequestContext,
+                       __in PDokanFCB FcbRelatedTo, __in PDokanFCB Fcb) {
+  if (DokanFCBFlagsIsSet(Fcb, DOKAN_FILE_DIRECTORY)) {
+    DOKAN_LOG_FINE_IRP(RequestContext, "FCB=%p is directory so skip it.", Fcb);
+    return;
+  }
+
+  DOKAN_LOG_FINE_IRP(RequestContext, "Check \"%wZ\" if is related to \"%wZ\"",
+                     &Fcb->FileName, &FcbRelatedTo->FileName);
 
-  if (fcbRelatedTo == NULL) {
+  if (!StartsWith(&Fcb->FileName, &FcbRelatedTo->FileName)) {
+    return;
+  }
+  DOKAN_LOG_FINE_IRP(RequestContext, "Flush \"%wZ\" if it is possible.",
+                     &Fcb->FileName);
+  FlushFcb(RequestContext, Fcb, NULL);
+}
+
+VOID FlushAllCachedFcb(__in PREQUEST_CONTEXT RequestContext,
+                       __in PDokanFCB FcbRelatedTo,
+                       __in_opt PFILE_OBJECT FileObject) {
+  if (FcbRelatedTo == NULL) {
     return;
   }
 
-  if (!DokanFCBFlagsIsSet(fcbRelatedTo, DOKAN_FILE_DIRECTORY)) {
+  if (!DokanFCBFlagsIsSet(FcbRelatedTo, DOKAN_FILE_DIRECTORY)) {
     DOKAN_LOG_FINE_IRP(
         RequestContext,
         "FlushAllCachedFcb file passed in. Flush only: FCB=%p FileObject=%p.",
-        fcbRelatedTo, fileObject);
-    FlushFcb(RequestContext, fcbRelatedTo, fileObject);
+        FcbRelatedTo, FileObject);
+    FlushFcb(RequestContext, FcbRelatedTo, FileObject);
     return;
   }
 
-  DokanVCBLockRW(fcbRelatedTo->Vcb);
+  DokanVCBLockRW(FcbRelatedTo->Vcb);
 
-  listHead = &fcbRelatedTo->Vcb->NextFCB;
-
-  for (thisEntry = listHead->Flink; thisEntry != listHead;
-       thisEntry = nextEntry) {
-    nextEntry = thisEntry->Flink;
-
-    fcb = CONTAINING_RECORD(thisEntry, DokanFCB, NextFCB);
-
-    if (DokanFCBFlagsIsSet(fcb, DOKAN_FILE_DIRECTORY)) {
-      DOKAN_LOG_FINE_IRP(RequestContext, "FCB=%p is directory so skip it.",
-                    fcb);
-      continue;
-    }
-
-    DOKAN_LOG_FINE_IRP(RequestContext, "Check \"%wZ\" if is related to \"%wZ\"", &fcb->FileName,
-                  &fcbRelatedTo->FileName);
-
-    if (StartsWith(&fcb->FileName, &fcbRelatedTo->FileName)) {
-      DOKAN_LOG_FINE_IRP(RequestContext, "Flush \"%wZ\" if it is possible.",
-                    &fcb->FileName);
-      FlushFcb(RequestContext, fcb, NULL);
-    }
-
-    fcb = NULL;
+  for (PDokanFCB *fcbInTable = (PDokanFCB *)RtlEnumerateGenericTableAvl(
+           &RequestContext->Vcb->FcbTable, /*Restart=*/TRUE);
+       fcbInTable != NULL;
+       fcbInTable = (PDokanFCB *)RtlEnumerateGenericTableAvl(
+           &RequestContext->Vcb->FcbTable, /*Restart=*/FALSE)) {
+    FlushIfDescendant(RequestContext, FcbRelatedTo, *fcbInTable);
   }
 
-  DokanVCBUnlock(fcbRelatedTo->Vcb);
+  DokanVCBUnlock(FcbRelatedTo->Vcb);
 
   DOKAN_LOG_FINE_IRP(RequestContext, "Finished");
 }
@@ -888,14 +886,11 @@ VOID DokanCompleteSetInformation(__in PREQUEST_CONTEXT RequestContext,
           __leave;
         }
 
-        fcb->FileName.Buffer = buffer;
-        ASSERT(fcb->FileName.Buffer != NULL);
-
-        RtlCopyMemory(fcb->FileName.Buffer, EventInfo->Buffer,
-                      EventInfo->BufferLength);
-
-        fcb->FileName.Length = (USHORT)EventInfo->BufferLength;
-        fcb->FileName.MaximumLength = (USHORT)EventInfo->BufferLength;
+        RtlCopyMemory(buffer, EventInfo->Buffer, EventInfo->BufferLength);
+        DokanVCBLockRW(RequestContext->Vcb);
+        DokanRenameFcb(RequestContext, fcb, buffer,
+                       (USHORT)EventInfo->BufferLength);
+        DokanVCBUnlock(RequestContext->Vcb);
         DOKAN_LOG_FINE_IRP(RequestContext, "Fcb=%p renamed \"%wZ\"", fcb,
                            &fcb->FileName);
       }

sys/fscontrol.c

@@ -859,6 +859,8 @@ NTSTATUS DokanMountVolume(__in PREQUEST_CONTEXT RequestContext) {
   }
 
   InitializeListHead(&vcb->NextFCB);
+  RtlInitializeGenericTableAvl(&vcb->FcbTable, DokanCompareFcb,
+                               DokanAllocateFcbAvl, DokanFreeFcbAvl, vcb);
 
   InitializeListHead(&vcb->DirNotifyList);
   FsRtlNotifyInitializeSync(&vcb->NotifySync);

sys/notification.c

@@ -366,6 +366,9 @@ NTSTATUS DokanEventRelease(__in_opt PREQUEST_CONTEXT RequestContext,
   DokanStopFcbGarbageCollectorThread(vcb);
   ClearLongFlag(vcb->Flags, VCB_MOUNTED);
 
+  if (vcb->FCBAvlNodeLookasideListInit) {
+    ExDeleteLookasideListEx(&vcb->FCBAvlNodeLookasideList);
+  }
   DokanCleanupAllChangeNotificationWaiters(vcb);
   IoReleaseRemoveLockAndWait(&dcb->RemoveLock, RequestContext);