From 88edf5723e505d4335acbbb36d9631c702efb905 Mon Sep 17 00:00:00 2001
From: Bill Zissimopoulos <billziss@navimatics.com>
Date: Thu, 8 Oct 2020 16:56:31 -0700
Subject: [PATCH] sys: notify implementation

---
 inc/winfsp/winfsp.h            | 40 +++++++++++++++++++++++++++++
 src/dll/fs.c                   | 46 ++++++++++++++++++++++++++++++++++
 tst/winfsp-tests/notify-test.c | 41 ++++++++++++++++++++++++++++++
 3 files changed, 127 insertions(+)

diff --git a/inc/winfsp/winfsp.h b/inc/winfsp/winfsp.h
index 15dd6a77..8677c96b 100644
--- a/inc/winfsp/winfsp.h
+++ b/inc/winfsp/winfsp.h
@@ -1186,9 +1186,49 @@ FSP_API VOID FspFileSystemStopDispatcher(FSP_FILE_SYSTEM *FileSystem);
  */
 FSP_API VOID FspFileSystemSendResponse(FSP_FILE_SYSTEM *FileSystem,
     FSP_FSCTL_TRANSACT_RSP *Response);
+/**
+ * Begin notifying Windows that the file system has file changes.
+ *
+ * A file system that wishes to notify Windows about file changes must
+ * first issue an FspFileSystemBegin call, followed by 0 or more
+ * FspFileSystemNotify calls, followed by an FspFileSystemNotifyEnd call.
+ *
+ * This operation blocks concurrent file rename operations. File rename
+ * operations may interfere with file notification, because a file being
+ * notified may also be concurrently renamed. After all file change
+ * notifications have been issued, you must make sure to call
+ * FspFileSystemNotifyEnd to allow file rename operations to proceed.
+ *
+ * @param FileSystem
+ *     The file system object.
+ * @return
+ *     STATUS_SUCCESS or error code. The error code STATUS_CANT_WAIT means that
+ *     a file rename operation is currently in progress and the operation must be
+ *     retried at a later time.
+ */
+FSP_API NTSTATUS FspFileSystemNotifyBegin(FSP_FILE_SYSTEM *FileSystem, ULONG Timeout);
+/**
+ * End notifying Windows that the file system has file changes.
+ *
+ * A file system that wishes to notify Windows about file changes must
+ * first issue an FspFileSystemBegin call, followed by 0 or more
+ * FspFileSystemNotify calls, followed by an FspFileSystemNotifyEnd call.
+ *
+ * This operation allows any blocked file rename operations to proceed.
+ *
+ * @param FileSystem
+ *     The file system object.
+ * @return
+ *     STATUS_SUCCESS or error code.
+ */
+FSP_API NTSTATUS FspFileSystemNotifyEnd(FSP_FILE_SYSTEM *FileSystem);
 /**
  * Notify Windows that the file system has file changes.
  *
+ * A file system that wishes to notify Windows about file changes must
+ * first issue an FspFileSystemBegin call, followed by 0 or more
+ * FspFileSystemNotify calls, followed by an FspFileSystemNotifyEnd call.
+ *
  * @param FileSystem
  *     The file system object.
  * @param NotifyInfo
diff --git a/src/dll/fs.c b/src/dll/fs.c
index 4f926b59..d0d525bc 100644
--- a/src/dll/fs.c
+++ b/src/dll/fs.c
@@ -432,6 +432,52 @@ FSP_API FSP_FILE_SYSTEM_OPERATION_CONTEXT *FspFileSystemGetOperationContext(VOID
     return (FSP_FILE_SYSTEM_OPERATION_CONTEXT *)TlsGetValue(FspFileSystemTlsKey);
 }
 
+FSP_API NTSTATUS FspFileSystemNotifyBegin(FSP_FILE_SYSTEM *FileSystem, ULONG Timeout)
+{
+    static const ULONG Delays[] =
+    {
+         10/*ms*/,
+         10/*ms*/,
+         50/*ms*/,
+         50/*ms*/,
+        100/*ms*/,
+        100/*ms*/,
+        300/*ms*/,
+    };
+    ULONG Total = 0, Delay;
+    NTSTATUS Result;
+
+    for (ULONG i = 0, n = sizeof(Delays) / sizeof(Delays[0]);; i++)
+    {
+        Result = FspFsctlNotify(FileSystem->VolumeHandle, 0, 0);
+        if (STATUS_CANT_WAIT != Result)
+            return Result;
+
+        Delay = n > i ? Delays[i] : Delays[n - 1];
+        if (INFINITE == Timeout)
+            Sleep(Delay);
+        else
+        {
+            if (Total >= Timeout)
+                break;
+            if (Total + Delay > Timeout)
+                Delay = Timeout - Total;
+            Total += Delay;
+            Sleep(Delay);
+        }
+    }
+
+    return Result;
+}
+
+FSP_API NTSTATUS FspFileSystemNotifyEnd(FSP_FILE_SYSTEM *FileSystem)
+{
+    FSP_FSCTL_NOTIFY_INFO NotifyInfo;
+
+    memset(&NotifyInfo, 0, sizeof NotifyInfo);
+    return FspFsctlNotify(FileSystem->VolumeHandle, &NotifyInfo, sizeof NotifyInfo.Size);
+}
+
 FSP_API NTSTATUS FspFileSystemNotify(FSP_FILE_SYSTEM *FileSystem,
     FSP_FSCTL_NOTIFY_INFO *NotifyInfo, SIZE_T Size)
 {
diff --git a/tst/winfsp-tests/notify-test.c b/tst/winfsp-tests/notify-test.c
index 3482f731..2bcbcaa9 100644
--- a/tst/winfsp-tests/notify-test.c
+++ b/tst/winfsp-tests/notify-test.c
@@ -111,11 +111,52 @@ void notify_abandon_rename_test(void)
         notify_abandon_rename_dotest(MemfsNet, L"\\\\memfs\\share");
 }
 
+static
+void notify_timeout_dotest(ULONG Flags)
+{
+    void *memfs = memfs_start(Flags);
+    FSP_FILE_SYSTEM *FileSystem = MemfsFileSystem(memfs);
+    NTSTATUS Result;
+
+    Result = FspFsctlNotify(FileSystem->VolumeHandle, 0, 0);
+    ASSERT(STATUS_SUCCESS == Result);
+
+    Result = FspFileSystemNotifyBegin(FileSystem, 0);
+    ASSERT(STATUS_CANT_WAIT == Result);
+
+    Result = FspFileSystemNotifyBegin(FileSystem, 9);
+    ASSERT(STATUS_CANT_WAIT == Result);
+
+    Result = FspFileSystemNotifyBegin(FileSystem, 10);
+    ASSERT(STATUS_CANT_WAIT == Result);
+
+    Result = FspFileSystemNotifyBegin(FileSystem, 11);
+    ASSERT(STATUS_CANT_WAIT == Result);
+
+    Result = FspFileSystemNotifyBegin(FileSystem, 20);
+    ASSERT(STATUS_CANT_WAIT == Result);
+
+    Result = FspFileSystemNotifyBegin(FileSystem, 1000);
+    ASSERT(STATUS_CANT_WAIT == Result);
+
+    memfs_stop(memfs);
+}
+
+static
+void notify_timeout_test(void)
+{
+    if (WinFspDiskTests)
+        notify_timeout_dotest(MemfsDisk);
+    if (WinFspNetTests)
+        notify_timeout_dotest(MemfsNet);
+}
+
 void notify_tests(void)
 {
     if (!OptExternal)
     {
         TEST(notify_abandon_test);
         TEST(notify_abandon_rename_test);
+        TEST(notify_timeout_test);
     }
 }