From b488ce077ce235d4e05be8c9b1bd7d6748599a54 Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Mon, 1 Jan 2018 20:35:13 +0000
Subject: Refactor to allow read to only wait on overlapping writes

---
 netfs/fuse/fuseApp.h     |  3 ++
 netfs/fuse/fuseFiles.cpp | 73 ++++++++++++++++++++++++++++--------------------
 2 files changed, 45 insertions(+), 31 deletions(-)

diff --git a/netfs/fuse/fuseApp.h b/netfs/fuse/fuseApp.h
index 9486e41..41ff9ad 100644
--- a/netfs/fuse/fuseApp.h
+++ b/netfs/fuse/fuseApp.h
@@ -115,6 +115,9 @@ namespace NetFS {
 			template<typename Handle>
 			std::map<int, Handle> & getMap();
 
+			template<typename Rtn, typename F> static inline Rtn
+				waitOnWriteRangeAndThen(size_t s, off_t o, const OpenFilePtr & of, const F & f);
+
 			ReqEnv reqEnv();
 
 			Ice::StringSeq args;
diff --git a/netfs/fuse/fuseFiles.cpp b/netfs/fuse/fuseFiles.cpp
index b587809..222cab0 100644
--- a/netfs/fuse/fuseFiles.cpp
+++ b/netfs/fuse/fuseFiles.cpp
@@ -106,14 +106,47 @@ FuseApp::flush(const char *, struct fuse_file_info * fi)
 	}
 }
 
+template<typename Rtn, typename F>
+inline
+Rtn
+FuseApp::waitOnWriteRangeAndThen(size_t s, off_t o, const OpenFilePtr & of, const F & f)
+{
+	const auto key = OpenFile::range(o, s);
+	while (true) {
+		std::unique_lock<decltype(of->_lock)> _l(of->_lock);
+		// Acquire operations to wait for
+		auto R = of->bg.equal_range(key);
+		if (R.first == R.second) {
+			// Perform operation
+			return f(key);
+		}
+		else {
+			// Wait for them whilst unlocked
+			_l.release()->unlock();
+			std::vector<Ice::AsyncResultPtr> overlap;
+			overlap.reserve(std::distance(R.first, R.second));
+			for (auto i = R.first; i != R.second; i++) {
+				overlap.push_back(i->second);
+			}
+			for (const auto & r : overlap) {
+				r->waitForCompleted();
+			}
+			// Cause this thread to yield so the callback can acquire _lock
+			usleep(0);
+		}
+	}
+}
+
 int
 FuseApp::read(const char *, char * buf, size_t s, off_t o, struct fuse_file_info * fi)
 {
 	try {
 		auto of = getProxy<OpenFilePtr>(fi->fh);
-		of->wait();
 		auto remote = of->remote;
-		Buffer data = remote->read(o, s);
+		auto data = (fcr->Async) ?
+			waitOnWriteRangeAndThen<Buffer>(s, o, of, [o, s, &remote](const auto &){
+				return remote->read(o, s);
+			}) : remote->read(o, s);
 		memcpy(buf, &data.front(), data.size());
 		return data.size();
 	}
@@ -129,36 +162,14 @@ FuseApp::write(const char *, const char * buf, size_t s, off_t o, struct fuse_fi
 		auto of = getProxy<OpenFilePtr>(fi->fh);
 		auto remote = of->remote;
 		if (fcr->Async) {
-			const auto key = OpenFile::range(o, s);
-			while (true) {
-				std::unique_lock<decltype(of->_lock)> _l(of->_lock);
-				// Acquire operations to wait for
-				std::vector<Ice::AsyncResultPtr> overlap;
-				auto R = of->bg.equal_range(key);
-				if (R.first == R.second) {
-					// Begin write and store operation
-					auto r = remote->begin_write(o, s, Buffer(buf, buf + s), [of,key](const Ice::AsyncResultPtr &) {
-						ScopeLock(of->_lock) {
-							of->bg.erase(key);
-						}
-					});
-					of->bg.insert({key, r});
-					break;
-				}
-				else {
-					// Wait for them whilst unlocked
-					_l.release()->unlock();
-					overlap.reserve(std::distance(R.first, R.second));
-					for (auto i = R.first; i != R.second; i++) {
-						overlap.push_back(i->second);
-					}
-					for (const auto & r : overlap) {
-						r->waitForCompleted();
+			waitOnWriteRangeAndThen<void>(s, o, of, [o, s, buf, &of, &remote](const auto & key){
+				auto r = remote->begin_write(o, s, Buffer(buf, buf + s), [of,key](const Ice::AsyncResultPtr &) {
+					ScopeLock(of->_lock) {
+						of->bg.erase(key);
 					}
-					// Cause this thread to yield so the callback can acquire _lock
-					usleep(0);
-				}
-			}
+				});
+				of->bg.insert({key, r});
+			});
 		}
 		else {
 			remote->write(o, s, Buffer(buf, buf + s));
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