refactor: introduce a more general LockDirectories for init

No functional change. This is in preparation for adding additional directory
locks on startup.

src/bitcoind.cpp

@@ -228,10 +228,10 @@ static bool AppInit(NodeContext& node)
             return InitError(Untranslated("-daemon is not supported on this operating system"));
 #endif // HAVE_DECL_FORK
         }
-        // Lock data directory after daemonization
-        if (!AppInitLockDataDirectory())
+        // Lock critical directories after daemonization
+        if (!AppInitLockDirectories())
         {
-            // If locking the data directory failed, exit immediately
+            // If locking a directory failed, exit immediately
             return false;
         }
         fRet = AppInitInterfaces(node) && AppInitMain(node);

src/init.cpp

@@ -1072,19 +1072,22 @@ bool AppInitParameterInteraction(const ArgsManager& args)
     return true;
 }
 
-static bool LockDataDirectory(bool probeOnly)
+static bool LockDirectory(const fs::path& dir, bool probeOnly)
 {
-    // Make sure only a single Bitcoin process is using the data directory.
-    const fs::path& datadir = gArgs.GetDataDirNet();
-    switch (util::LockDirectory(datadir, ".lock", probeOnly)) {
+    // Make sure only a single process is using the directory.
+    switch (util::LockDirectory(dir, ".lock", probeOnly)) {
     case util::LockResult::ErrorWrite:
-        return InitError(strprintf(_("Cannot write to data directory '%s'; check permissions."), fs::PathToString(datadir)));
+        return InitError(strprintf(_("Cannot write to directory '%s'; check permissions."), fs::PathToString(dir)));
     case util::LockResult::ErrorLock:
-        return InitError(strprintf(_("Cannot obtain a lock on data directory %s. %s is probably already running."), fs::PathToString(datadir), CLIENT_NAME));
+        return InitError(strprintf(_("Cannot obtain a lock on directory %s. %s is probably already running."), fs::PathToString(dir), CLIENT_NAME));
     case util::LockResult::Success: return true;
     } // no default case, so the compiler can warn about missing cases
     assert(false);
 }
+static bool LockDirectories(bool probeOnly)
+{
+    return LockDirectory(gArgs.GetDataDirNet(), probeOnly);
+}
 
 bool AppInitSanityChecks(const kernel::Context& kernel)
 {
@@ -1099,19 +1102,19 @@ bool AppInitSanityChecks(const kernel::Context& kernel)
         return InitError(strprintf(_("Elliptic curve cryptography sanity check failure. %s is shutting down."), CLIENT_NAME));
     }
 
-    // Probe the data directory lock to give an early error message, if possible
-    // We cannot hold the data directory lock here, as the forking for daemon() hasn't yet happened,
-    // and a fork will cause weird behavior to it.
-    return LockDataDirectory(true);
+    // Probe the directory locks to give an early error message, if possible
+    // We cannot hold the directory locks here, as the forking for daemon() hasn't yet happened,
+    // and a fork will cause weird behavior to them.
+    return LockDirectories(true);
 }
 
-bool AppInitLockDataDirectory()
+bool AppInitLockDirectories()
 {
-    // After daemonization get the data directory lock again and hold on to it until exit
+    // After daemonization get the directory locks again and hold on to them until exit
     // This creates a slight window for a race condition to happen, however this condition is harmless: it
     // will at most make us exit without printing a message to console.
-    if (!LockDataDirectory(false)) {
-        // Detailed error printed inside LockDataDirectory
+    if (!LockDirectories(false)) {
+        // Detailed error printed inside LockDirectory
         return false;
     }
     return true;

src/init.h

@@ -55,11 +55,11 @@ bool AppInitParameterInteraction(const ArgsManager& args);
  */
 bool AppInitSanityChecks(const kernel::Context& kernel);
 /**
- * Lock bitcoin core data directory.
+ * Lock bitcoin core critical directories.
  * @note This should only be done after daemonization. Do not call Shutdown() if this function fails.
  * @pre Parameters should be parsed and config file should be read, AppInitSanityChecks should have been called.
  */
-bool AppInitLockDataDirectory();
+bool AppInitLockDirectories();
 /**
  * Initialize node and wallet interface pointers. Has no prerequisites or side effects besides allocating memory.
  */
@@ -67,7 +67,7 @@ bool AppInitInterfaces(node::NodeContext& node);
 /**
  * Bitcoin core main initialization.
  * @note This should only be done after daemonization. Call Shutdown() if this function fails.
- * @pre Parameters should be parsed and config file should be read, AppInitLockDataDirectory should have been called.
+ * @pre Parameters should be parsed and config file should be read, AppInitLockDirectories should have been called.
  */
 bool AppInitMain(node::NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info = nullptr);
 

src/node/interfaces.cpp

@@ -116,7 +116,7 @@ public:
         m_context->ecc_context = std::make_unique<ECC_Context>();
         if (!AppInitSanityChecks(*m_context->kernel)) return false;
 
-        if (!AppInitLockDataDirectory()) return false;
+        if (!AppInitLockDirectories()) return false;
         if (!AppInitInterfaces(*m_context)) return false;
 
         return true;

test/functional/feature_filelock.py

@@ -30,7 +30,7 @@ class FilelockTest(BitcoinTestFramework):
         self.log.info(f"Using datadir {datadir}")
 
         self.log.info("Check that we can't start a second bitcoind instance using the same datadir")
-        expected_msg = f"Error: Cannot obtain a lock on data directory {datadir}. {self.config['environment']['CLIENT_NAME']} is probably already running."
+        expected_msg = f"Error: Cannot obtain a lock on directory {datadir}. {self.config['environment']['CLIENT_NAME']} is probably already running."
         self.nodes[1].assert_start_raises_init_error(extra_args=[f'-datadir={self.nodes[0].datadir_path}', '-noserver'], expected_msg=expected_msg)
 
         self.log.info("Check that cookie and PID file are not deleted when attempting to start a second bitcoind using the same datadir")