* FileCacheReadRequest: Implemented work-around for the problem that

file_cache_read() will reenter the file system which will overwrite the
  buffer associated with the port, so we can't allocate space in the buffer
  before calling it.
* FileCacheWriteRequest still has a similar problem, though it's probably better
  to rethink the kernel-userland communication completely.

BFS basically seems to work in userland, now. Didn't really test write
operations though. They will probably run into problems due to the issue above.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@29555 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/add-ons/kernel/file_systems/userlandfs/kernel_add_on/KernelRequestHandler.cpp

@@ -14,6 +14,9 @@
 
 #include <NodeMonitor.h>
 
+#include <AutoDeleter.h>
+
+
 // VolumePutter
 class VolumePutter {
 public:
@@ -644,6 +647,10 @@ KernelRequestHandler::_HandleRequest(FileCacheReadRequest* request)
 
 	size_t size = request->size;
 
+// TODO: Allocating the reply and the buffer first now would save an allocation
+// and copying the buffer, but since Volume::ReadFileCache() will reenter the
+// file system (io() hook) our allocation would be overwritten.
+#if 0
 	// allocate the reply
 	RequestAllocator allocator(fPort->GetPort());
 	FileCacheReadReply* reply;
@@ -662,6 +669,31 @@ KernelRequestHandler::_HandleRequest(FileCacheReadRequest* request)
 		result = volume->ReadFileCache(request->vnid, request->cookie,
 			request->pos, buffer, &size);
 	}
+#else
+	// allocate a buffer
+	void* buffer = malloc(size);
+		// TODO: Limit size!
+	if (buffer == NULL)
+		result = B_NO_MEMORY;
+	MemoryDeleter _2(buffer);
+
+	// execute the request
+	if (result == B_OK) {
+		result = volume->ReadFileCache(request->vnid, request->cookie,
+			request->pos, buffer, &size);
+	}
+
+	// allocate the reply
+	RequestAllocator allocator(fPort->GetPort());
+	FileCacheReadReply* reply;
+	status_t error = AllocateRequest(allocator, &reply);
+	if (error != B_OK)
+		RETURN_ERROR(error);
+
+	error = allocator.AllocateData(reply->buffer, buffer, size, 1, false);
+	if (error != B_OK)
+		return error;
+#endif
 
 	// prepare the reply
 	reply->error = result;
@@ -689,6 +721,8 @@ KernelRequestHandler::_HandleRequest(FileCacheWriteRequest* request)
 	size_t size = 0;
 	if (result == B_OK) {
 		size = request->buffer.GetSize();
+// TODO: WriteFileCache() will reenter the file system (io() hook) which will
+// overwrite the request and the buffer!
 		result = volume->WriteFileCache(request->vnid, request->cookie,
 			request->pos, request->buffer.GetData(), &size);
 	}