From 0f778a0a38e6ef81f76629fec2428745fccbf33a Mon Sep 17 00:00:00 2001
From: Joe Thornber <ejt@redhat.com>
Date: Tue, 14 Jun 2016 16:26:37 +0100
Subject: [PATCH] [block-cache] FIx some bugs in the io engine

---
 block-cache/io_engine.cc | 61 +++++++++++++++++++++++++++++-----------
 block-cache/io_engine.h  | 22 ++++++++++-----
 2 files changed, 60 insertions(+), 23 deletions(-)

diff --git a/block-cache/io_engine.cc b/block-cache/io_engine.cc
index a4211cb..2fe4082 100644
--- a/block-cache/io_engine.cc
+++ b/block-cache/io_engine.cc
@@ -14,13 +14,6 @@ using namespace std;
 
 //----------------------------------------------------------------
 
-namespace {
-	unsigned const SECTOR_SHIFT = 9;
-	unsigned const PAGE_SIZE = 4096;
-}
-
-//----------------------------------------------------------------
-
 control_block_set::control_block_set(unsigned nr)
 	: cbs_(nr)
 {
@@ -77,7 +70,7 @@ aio_engine::~aio_engine()
 aio_engine::handle
 aio_engine::open_file(std::string const &path, mode m, sharing s)
 {
-	int flags = (m == READ_ONLY) ? O_RDONLY : O_RDWR;
+	int flags = (m == M_READ_ONLY) ? O_RDONLY : O_RDWR;
 	if (s == EXCLUSIVE)
 		flags |= O_EXCL;
 	int fd = ::open(path.c_str(), O_DIRECT | flags);
@@ -126,45 +119,81 @@ aio_engine::issue_io(handle h, dir d, sector_t b, sector_t e, void *data, unsign
 	cb->u.c.buf = data;
 	cb->u.c.offset = b << SECTOR_SHIFT;
 	cb->u.c.nbytes = (e - b) << SECTOR_SHIFT;
-	cb->aio_lio_opcode = (d == READ) ? IO_CMD_PREAD : IO_CMD_PWRITE;
+	cb->aio_lio_opcode = (d == D_READ) ? IO_CMD_PREAD : IO_CMD_PWRITE;
 
 	int r = io_submit(aio_context_, 1, &cb);
 	return r == 1;
 }
 
-std::pair<bool, io_engine::handle>
+optional<io_engine::wait_result>
 aio_engine::wait()
+{
+	return wait_(NULL);
+}
+
+optional<io_engine::wait_result>
+aio_engine::wait(unsigned &microsec)
+{
+	timespec start = micro_to_ts(microsec);
+	timespec stop = start;
+	auto r = wait_(&stop);
+	microsec = ts_to_micro(stop) - microsec;
+	return r;
+}
+
+boost::optional<io_engine::wait_result>
+aio_engine::wait_(timespec *ts)
 {
 	int r;
 	struct io_event event;
 
 	memset(&event, 0, sizeof(event));
-
-	r = io_getevents(aio_context_, 1, 1, &event, NULL);
+	r = io_getevents(aio_context_, 1, 1, &event, ts);
 	if (r < 0) {
 		std::ostringstream out;
 		out << "io_getevents failed: " << r;
 		throw std::runtime_error(out.str());
 	}
 
+	if (r == 0) {
+		return optional<wait_result>();
+	}
+
 	iocb *cb = reinterpret_cast<iocb *>(event.obj);
 	unsigned context = cbs_.context(cb);
 
 	if (event.res == cb->u.c.nbytes) {
 		cbs_.free(cb);
-		return make_pair(true, context);
+		return optional<wait_result>(make_pair(true, context));
 
 	} else if (static_cast<int>(event.res) < 0) {
 		cbs_.free(cb);
-		return make_pair(false, context);
+		return optional<wait_result>(make_pair(false, context));
 
 	} else {
 		cbs_.free(cb);
-		return make_pair(false, context);
+		return optional<wait_result>(make_pair(false, context));
 	}
 
 	// shouldn't get here
-	return make_pair(false, 0);
+	return optional<wait_result>(make_pair(false, 0));
+}
+
+struct timespec
+aio_engine::micro_to_ts(unsigned micro)
+{
+	timespec ts;
+	ts.tv_sec = micro / 1000000u;
+	ts.tv_nsec = (micro % 1000000) * 1000;
+	return ts;
+}
+
+unsigned
+aio_engine::ts_to_micro(timespec const &ts)
+{
+	unsigned micro = ts.tv_sec * 1000000;
+	micro += ts.tv_nsec / 1000;
+	return micro;
 }
 
 //----------------------------------------------------------------
diff --git a/block-cache/io_engine.h b/block-cache/io_engine.h
index f9e4c9c..fd902c1 100644
--- a/block-cache/io_engine.h
+++ b/block-cache/io_engine.h
@@ -14,17 +14,20 @@
 namespace bcache {
 	using sector_t = uint64_t;
 
+	unsigned const SECTOR_SHIFT = 9;
+	unsigned const PAGE_SIZE = 4096;
+
 	// Virtual base class to aid unit testing
 	class io_engine {
 	public:
 		enum mode {
-			READ_ONLY,
-			READ_WRITE
+			M_READ_ONLY,
+			M_READ_WRITE
 		};
 
 		enum dir {
-			READ,
-			WRITE
+			D_READ,
+			D_WRITE
 		};
 
 		enum sharing {
@@ -46,7 +49,8 @@ namespace bcache {
 
 		// returns (success, context)
 		using wait_result = std::pair<bool, unsigned>;
-		virtual wait_result wait() = 0;
+		virtual boost::optional<wait_result> wait() = 0;
+		virtual boost::optional<wait_result> wait(unsigned &microsec) = 0;
 
 	private:
 		io_engine(io_engine const &) = delete;
@@ -90,10 +94,14 @@ namespace bcache {
 		// Returns false if queueing the io failed
 		virtual bool issue_io(handle h, dir d, sector_t b, sector_t e, void *data, unsigned context);
 
-		// returns (success, context)
-		virtual wait_result wait();
+		virtual boost::optional<wait_result> wait();
+		virtual boost::optional<wait_result> wait(unsigned &microsec);
 
 	private:
+		static struct timespec micro_to_ts(unsigned micro);
+		static unsigned ts_to_micro(timespec const &ts);
+		boost::optional<io_engine::wait_result> wait_(timespec *ts);
+
 		std::list<base::unique_fd> descriptors_;
 
 		io_context_t aio_context_;