From de3bb58078cdcaf357a9a0c37648596c85615bc2 Mon Sep 17 00:00:00 2001
From: "Steinar H. Gunderson" <steinar+git@gunderson.no>
Date: Tue, 27 Jul 2021 15:45:27 +0200
Subject: [PATCH] Send the result value of the stat to the callback.

---
 access_rx_cache.cpp |  2 +-
 io_uring_engine.cpp |  6 +++---
 io_uring_engine.h   | 14 ++++++--------
 3 files changed, 10 insertions(+), 12 deletions(-)

diff --git a/access_rx_cache.cpp b/access_rx_cache.cpp
index b6db4ea..7633c31 100644
--- a/access_rx_cache.cpp
+++ b/access_rx_cache.cpp
@@ -55,7 +55,7 @@ void AccessRXCache::check_access(const char *filename, bool allow_async, functio
 			it->second.emplace_back(PendingStat{ filename, move(cb) });
 		} else {
 			it = pending_stats.emplace(filename, vector<PendingStat>{}).first;
-			engine->submit_stat(filename, [this, it, filename{ strdup(filename) }, cb{ move(cb) }] {
+			engine->submit_stat(filename, [this, it, filename{ strdup(filename) }, cb{ move(cb) }](bool) {
 				// The stat returned, so now do the actual access() calls.
 				// All of them should be in cache, so don't fire off new statx()
 				// calls during that check.
diff --git a/io_uring_engine.cpp b/io_uring_engine.cpp
index ab9f411..116cf85 100644
--- a/io_uring_engine.cpp
+++ b/io_uring_engine.cpp
@@ -46,7 +46,7 @@ IOUringEngine::IOUringEngine(size_t slop_bytes)
 #endif
 }
 
-void IOUringEngine::submit_stat(const char *path, std::function<void()> cb)
+void IOUringEngine::submit_stat(const char *path, std::function<void(bool)> cb)
 {
 	assert(supports_stat);
 
@@ -115,7 +115,7 @@ void IOUringEngine::submit_read_internal(io_uring_sqe *sqe, int fd, size_t len,
 	++pending_reads;
 }
 
-void IOUringEngine::submit_stat_internal(io_uring_sqe *sqe, char *path, std::function<void()> cb)
+void IOUringEngine::submit_stat_internal(io_uring_sqe *sqe, char *path, std::function<void(bool)> cb)
 {
 	PendingRead *pending = new PendingRead;
 	pending->op = OP_STAT;
@@ -166,7 +166,7 @@ void IOUringEngine::finish()
 				--pending_reads;
 
 				size_t old_pending_reads = pending_reads;
-				pending->stat_cb();
+				pending->stat_cb(cqe->res == 0);
 				free(pending->stat.pathname);
 				delete pending->stat.buf;
 				delete pending;
diff --git a/io_uring_engine.h b/io_uring_engine.h
index 470bacf..688a6ae 100644
--- a/io_uring_engine.h
+++ b/io_uring_engine.h
@@ -18,11 +18,9 @@ public:
 	IOUringEngine(size_t slop_bytes);
 	void submit_read(int fd, size_t len, off_t offset, std::function<void(std::string_view)> cb);
 
-	// NOTE: We just do the stat() to get the data into the dentry cache for fast access;
-	// we don't care about the return value. Thus, the callback has no parameter lists.
-	// If we have no io_uring, the callback will be made immediately, with no stat() call
-	// being done.
-	void submit_stat(const char *path, std::function<void()> cb);
+	// NOTE: We just do the stat() to get the data into the dentry cache for fast access,
+	// or to check whether the file exists. Thus, the callback has only an OK/not OK boolean.
+	void submit_stat(const char *path, std::function<void(bool ok)> cb);
 	bool get_supports_stat() { return supports_stat; }
 
 	void finish();
@@ -31,7 +29,7 @@ public:
 private:
 #ifndef WITHOUT_URING
 	void submit_read_internal(io_uring_sqe *sqe, int fd, size_t len, off_t offset, std::function<void(std::string_view)> cb);
-	void submit_stat_internal(io_uring_sqe *sqe, char *path, std::function<void()> cb);
+	void submit_stat_internal(io_uring_sqe *sqe, char *path, std::function<void(bool)> cb);
 
 	io_uring ring;
 #endif
@@ -49,7 +47,7 @@ private:
 
 	struct QueuedStat {
 		char *pathname;  // Owned by us.
-		std::function<void()> cb;
+		std::function<void(bool)> cb;
 	};
 	std::queue<QueuedStat> queued_stats;
 
@@ -60,7 +58,7 @@ private:
 		Op op;
 
 		std::function<void(std::string_view)> read_cb;
-		std::function<void()> stat_cb;
+		std::function<void(bool)> stat_cb;
 
 		union {
 			struct {
-- 
2.39.2