From 8a7e04ffd3e582854f92989540a8aad6d052b7ff Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Wed, 25 Oct 2017 19:20:18 +0100
Subject: Add optimistic checking and pruning of background write results if it
 can be done without waiting for the lock

---
 netfs/fuse/fuseApp.h     |  2 ++
 netfs/fuse/fuseFiles.cpp | 25 ++++++++++++++++++++++++-
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/netfs/fuse/fuseApp.h b/netfs/fuse/fuseApp.h
index c37ba6d..2169e85 100644
--- a/netfs/fuse/fuseApp.h
+++ b/netfs/fuse/fuseApp.h
@@ -33,12 +33,14 @@ namespace NetFS {
 					OpenFile(FilePrx remote, const std::string & path, int flags);
 
 					void flush();
+					void nonBlockingFlush();
 					void wait() const;
 
 					FilePrx remote;
 					const std::string path;
 					const int flags;
 					std::list<Ice::AsyncResultPtr> bg;
+					mutable boost::shared_mutex _lock;
 			};
 			typedef IceUtil::Handle<OpenFile> OpenFilePtr;
 			typedef std::map<int, OpenFilePtr> OpenFiles;
diff --git a/netfs/fuse/fuseFiles.cpp b/netfs/fuse/fuseFiles.cpp
index e31b4db..e81dd45 100644
--- a/netfs/fuse/fuseFiles.cpp
+++ b/netfs/fuse/fuseFiles.cpp
@@ -39,6 +39,7 @@ NetFS::FuseApp::clearFileProxy(uint64_t localID)
 void
 NetFS::FuseApp::OpenFile::wait() const
 {
+	SharedLock(_lock);
 	for (const auto & w : bg) {
 		w->waitForCompleted();
 	}
@@ -47,6 +48,7 @@ NetFS::FuseApp::OpenFile::wait() const
 void
 NetFS::FuseApp::OpenFile::flush()
 {
+	Lock(_lock);
 	while (!bg.empty()) {
 		auto w = bg.front();
 		bg.pop_front();
@@ -55,6 +57,24 @@ NetFS::FuseApp::OpenFile::flush()
 	}
 }
 
+void
+NetFS::FuseApp::OpenFile::nonBlockingFlush()
+{
+	boost::unique_lock<boost::shared_mutex> lock(_lock, boost::try_to_lock);
+	if (lock.owns_lock()) {
+		for (auto wi = bg.begin(); wi != bg.end(); ) {
+			auto w = *wi;
+			if (w->isCompleted()) {
+				wi = bg.erase(wi);
+				w->throwLocalException();
+			}
+			else {
+				wi++;
+			}
+		}
+	}
+}
+
 int
 NetFS::FuseApp::open(const char * p, struct fuse_file_info * fi)
 {
@@ -138,7 +158,10 @@ NetFS::FuseApp::write(const char *, const char * buf, size_t s, off_t o, struct
 		auto remote = of->remote;
 		auto r = remote->begin_write(o, s, NetFS::Buffer(buf, buf + s));
 		if (fcr->Async) {
-			of->bg.push_back(r);
+			ScopeLock(of->_lock) {
+				of->bg.push_back(r);
+			}
+			of->nonBlockingFlush();
 		}
 		else {
 			r->throwLocalException();
-- 
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