Merge bitcoin/bitcoin#28075: util: Remove DirIsWritable, GetUniquePath

fa3da629a1 Remove DirIsWritable, GetUniquePath (MarcoFalke)
fad3a9793b Return LockResult::ErrorWrite in LockDirectory (MarcoFalke)
fa0afe7408 refactor: Return enum in LockDirectory (MarcoFalke)

Pull request description:

  `GetUniquePath` is only used in tests and in `DirIsWritable`. The check by `DirIsWritable` is redundant with the check done in `LockDirectory`.

  Fix the redundancy by removing everything, except `LockDirectory`.

ACKs for top commit:
  TheCharlatan:
    Re-ACK fa3da629a1
  hebasto:
    ACK fa3da629a1, I have reviewed the code and it looks OK.

Tree-SHA512: e95f18cd586de7582e9c08ac7ddb860bfcfcbc8963804f45c5784c5e4c0598dc59ae7e45dd4daf30a5020dbf8433f5db2ad06e46a8676371982003790043c6c9

src/Makefile.am

@@ -304,7 +304,6 @@ BITCOIN_CORE_H = \
   util/fees.h \
   util/fs.h \
   util/fs_helpers.h \
-  util/getuniquepath.h \
   util/golombrice.h \
   util/hash_type.h \
   util/hasher.h \
@@ -741,7 +740,6 @@ libbitcoin_util_a_SOURCES = \
   util/fees.cpp \
   util/fs.cpp \
   util/fs_helpers.cpp \
-  util/getuniquepath.cpp \
   util/hasher.cpp \
   util/sock.cpp \
   util/syserror.cpp \
@@ -984,7 +982,6 @@ libbitcoinkernel_la_SOURCES = \
   util/exception.cpp \
   util/fs.cpp \
   util/fs_helpers.cpp \
-  util/getuniquepath.cpp \
   util/hasher.cpp \
   util/moneystr.cpp \
   util/rbf.cpp \

src/init.cpp

@@ -1047,13 +1047,14 @@ static bool LockDataDirectory(bool probeOnly)
 {
     // Make sure only a single Bitcoin process is using the data directory.
     const fs::path& datadir = gArgs.GetDataDirNet();
-    if (!DirIsWritable(datadir)) {
+    switch (util::LockDirectory(datadir, ".lock", probeOnly)) {
+    case util::LockResult::ErrorWrite:
         return InitError(strprintf(_("Cannot write to data directory '%s'; check permissions."), fs::PathToString(datadir)));
-    }
-    if (!LockDirectory(datadir, ".lock", probeOnly)) {
+    case util::LockResult::ErrorLock:
         return InitError(strprintf(_("Cannot obtain a lock on data directory %s. %s is probably already running."), fs::PathToString(datadir), PACKAGE_NAME));
-    }
-    return true;
+    case util::LockResult::Success: return true;
+    } // no default case, so the compiler can warn about missing cases
+    assert(false);
 }
 
 bool AppInitSanityChecks(const kernel::Context& kernel)

src/test/fs_tests.cpp

@@ -5,7 +5,6 @@
 #include <test/util/setup_common.h>
 #include <util/fs.h>
 #include <util/fs_helpers.h>
-#include <util/getuniquepath.h>
 
 #include <boost/test/unit_test.hpp>
 
@@ -101,29 +100,14 @@ BOOST_AUTO_TEST_CASE(fsbridge_fstream)
         BOOST_CHECK_EQUAL(tmpfile1, fsbridge::AbsPathJoin(tmpfile1, ""));
         BOOST_CHECK_EQUAL(tmpfile1, fsbridge::AbsPathJoin(tmpfile1, {}));
     }
-    {
-        fs::path p1 = GetUniquePath(tmpfolder);
-        fs::path p2 = GetUniquePath(tmpfolder);
-        fs::path p3 = GetUniquePath(tmpfolder);
-
-        // Ensure that the parent path is always the same.
-        BOOST_CHECK_EQUAL(tmpfolder, p1.parent_path());
-        BOOST_CHECK_EQUAL(tmpfolder, p2.parent_path());
-        BOOST_CHECK_EQUAL(tmpfolder, p3.parent_path());
-
-        // Ensure that generated paths are actually different.
-        BOOST_CHECK(p1 != p2);
-        BOOST_CHECK(p2 != p3);
-        BOOST_CHECK(p1 != p3);
-    }
 }
 
 BOOST_AUTO_TEST_CASE(rename)
 {
     const fs::path tmpfolder{m_args.GetDataDirBase()};
 
-    const fs::path path1{GetUniquePath(tmpfolder)};
-    const fs::path path2{GetUniquePath(tmpfolder)};
+    const fs::path path1{tmpfolder / "a"};
+    const fs::path path2{tmpfolder / "b"};
 
     const std::string path1_contents{"1111"};
     const std::string path2_contents{"2222"};
@@ -158,13 +142,13 @@ BOOST_AUTO_TEST_CASE(create_directories)
     // Test fs::create_directories workaround.
     const fs::path tmpfolder{m_args.GetDataDirBase()};
 
-    const fs::path dir{GetUniquePath(tmpfolder)};
+    const fs::path dir{tmpfolder / "a"};
     fs::create_directory(dir);
     BOOST_CHECK(fs::exists(dir));
     BOOST_CHECK(fs::is_directory(dir));
     BOOST_CHECK(!fs::create_directories(dir));
 
-    const fs::path symlink{GetUniquePath(tmpfolder)};
+    const fs::path symlink{tmpfolder / "b"};
     fs::create_directory_symlink(dir, symlink);
     BOOST_CHECK(fs::exists(symlink));
     BOOST_CHECK(fs::is_symlink(symlink));

src/test/util_tests.cpp

@@ -12,7 +12,6 @@
 #include <util/bitdeque.h>
 #include <util/fs.h>
 #include <util/fs_helpers.h>
-#include <util/getuniquepath.h>
 #include <util/message.h> // For MessageSign(), MessageVerify(), MESSAGE_MAGIC
 #include <util/moneystr.h>
 #include <util/overflow.h>
@@ -1106,15 +1105,16 @@ BOOST_AUTO_TEST_CASE(test_ParseFixedPoint)
     BOOST_CHECK(!ParseFixedPoint("31.999999999999999999999", 3, &amount));
 }
 
-static void TestOtherThread(fs::path dirname, fs::path lockname, bool *result)
-{
-    *result = LockDirectory(dirname, lockname);
-}
-
 #ifndef WIN32 // Cannot do this test on WIN32 due to lack of fork()
 static constexpr char LockCommand = 'L';
 static constexpr char UnlockCommand = 'U';
 static constexpr char ExitCommand = 'X';
+enum : char {
+    ResSuccess = 2, // Start with 2 to avoid accidental collision with common values 0 and 1
+    ResErrorWrite,
+    ResErrorLock,
+    ResUnlockSuccess,
+};
 
 [[noreturn]] static void TestOtherProcess(fs::path dirname, fs::path lockname, int fd)
 {
@@ -1122,15 +1122,22 @@ static constexpr char ExitCommand = 'X';
     while (true) {
         int rv = read(fd, &ch, 1); // Wait for command
         assert(rv == 1);
-        switch(ch) {
+        switch (ch) {
         case LockCommand:
-            ch = LockDirectory(dirname, lockname);
+            ch = [&] {
+                switch (util::LockDirectory(dirname, lockname)) {
+                case util::LockResult::Success: return ResSuccess;
+                case util::LockResult::ErrorWrite: return ResErrorWrite;
+                case util::LockResult::ErrorLock: return ResErrorLock;
+                } // no default case, so the compiler can warn about missing cases
+                assert(false);
+            }();
             rv = write(fd, &ch, 1);
             assert(rv == 1);
             break;
         case UnlockCommand:
             ReleaseDirectoryLocks();
-            ch = true; // Always succeeds
+            ch = ResUnlockSuccess; // Always succeeds
             rv = write(fd, &ch, 1);
             assert(rv == 1);
             break;
@@ -1165,53 +1172,58 @@ BOOST_AUTO_TEST_CASE(test_LockDirectory)
         TestOtherProcess(dirname, lockname, fd[0]);
     }
     BOOST_CHECK_EQUAL(close(fd[0]), 0); // Parent: close child end
+
+    char ch;
+    // Lock on non-existent directory should fail
+    BOOST_CHECK_EQUAL(write(fd[1], &LockCommand, 1), 1);
+    BOOST_CHECK_EQUAL(read(fd[1], &ch, 1), 1);
+    BOOST_CHECK_EQUAL(ch, ResErrorWrite);
 #endif
     // Lock on non-existent directory should fail
-    BOOST_CHECK_EQUAL(LockDirectory(dirname, lockname), false);
+    BOOST_CHECK_EQUAL(util::LockDirectory(dirname, lockname), util::LockResult::ErrorWrite);
 
     fs::create_directories(dirname);
 
     // Probing lock on new directory should succeed
-    BOOST_CHECK_EQUAL(LockDirectory(dirname, lockname, true), true);
+    BOOST_CHECK_EQUAL(util::LockDirectory(dirname, lockname, true), util::LockResult::Success);
 
     // Persistent lock on new directory should succeed
-    BOOST_CHECK_EQUAL(LockDirectory(dirname, lockname), true);
+    BOOST_CHECK_EQUAL(util::LockDirectory(dirname, lockname), util::LockResult::Success);
 
     // Another lock on the directory from the same thread should succeed
-    BOOST_CHECK_EQUAL(LockDirectory(dirname, lockname), true);
+    BOOST_CHECK_EQUAL(util::LockDirectory(dirname, lockname), util::LockResult::Success);
 
     // Another lock on the directory from a different thread within the same process should succeed
-    bool threadresult;
-    std::thread thr(TestOtherThread, dirname, lockname, &threadresult);
+    util::LockResult threadresult;
+    std::thread thr([&] { threadresult = util::LockDirectory(dirname, lockname); });
     thr.join();
-    BOOST_CHECK_EQUAL(threadresult, true);
+    BOOST_CHECK_EQUAL(threadresult, util::LockResult::Success);
 #ifndef WIN32
     // Try to acquire lock in child process while we're holding it, this should fail.
-    char ch;
     BOOST_CHECK_EQUAL(write(fd[1], &LockCommand, 1), 1);
     BOOST_CHECK_EQUAL(read(fd[1], &ch, 1), 1);
-    BOOST_CHECK_EQUAL((bool)ch, false);
+    BOOST_CHECK_EQUAL(ch, ResErrorLock);
 
     // Give up our lock
     ReleaseDirectoryLocks();
     // Probing lock from our side now should succeed, but not hold on to the lock.
-    BOOST_CHECK_EQUAL(LockDirectory(dirname, lockname, true), true);
+    BOOST_CHECK_EQUAL(util::LockDirectory(dirname, lockname, true), util::LockResult::Success);
 
     // Try to acquire the lock in the child process, this should be successful.
     BOOST_CHECK_EQUAL(write(fd[1], &LockCommand, 1), 1);
     BOOST_CHECK_EQUAL(read(fd[1], &ch, 1), 1);
-    BOOST_CHECK_EQUAL((bool)ch, true);
+    BOOST_CHECK_EQUAL(ch, ResSuccess);
 
     // When we try to probe the lock now, it should fail.
-    BOOST_CHECK_EQUAL(LockDirectory(dirname, lockname, true), false);
+    BOOST_CHECK_EQUAL(util::LockDirectory(dirname, lockname, true), util::LockResult::ErrorLock);
 
     // Unlock the lock in the child process
     BOOST_CHECK_EQUAL(write(fd[1], &UnlockCommand, 1), 1);
     BOOST_CHECK_EQUAL(read(fd[1], &ch, 1), 1);
-    BOOST_CHECK_EQUAL((bool)ch, true);
+    BOOST_CHECK_EQUAL(ch, ResUnlockSuccess);
 
     // When we try to probe the lock now, it should succeed.
-    BOOST_CHECK_EQUAL(LockDirectory(dirname, lockname, true), true);
+    BOOST_CHECK_EQUAL(util::LockDirectory(dirname, lockname, true), util::LockResult::Success);
 
     // Re-lock the lock in the child process, then wait for it to exit, check
     // successful return. After that, we check that exiting the process
@@ -1224,7 +1236,7 @@ BOOST_AUTO_TEST_CASE(test_LockDirectory)
     BOOST_CHECK_EQUAL(write(fd[1], &ExitCommand, 1), 1);
     BOOST_CHECK_EQUAL(waitpid(pid, &processstatus, 0), pid);
     BOOST_CHECK_EQUAL(processstatus, 0);
-    BOOST_CHECK_EQUAL(LockDirectory(dirname, lockname, true), true);
+    BOOST_CHECK_EQUAL(util::LockDirectory(dirname, lockname, true), util::LockResult::Success);
 
     // Restore SIGCHLD
     signal(SIGCHLD, old_handler);
@@ -1235,22 +1247,6 @@ BOOST_AUTO_TEST_CASE(test_LockDirectory)
     fs::remove_all(dirname);
 }
 
-BOOST_AUTO_TEST_CASE(test_DirIsWritable)
-{
-    // Should be able to write to the data dir.
-    fs::path tmpdirname = m_args.GetDataDirBase();
-    BOOST_CHECK_EQUAL(DirIsWritable(tmpdirname), true);
-
-    // Should not be able to write to a non-existent dir.
-    tmpdirname = GetUniquePath(tmpdirname);
-    BOOST_CHECK_EQUAL(DirIsWritable(tmpdirname), false);
-
-    fs::create_directory(tmpdirname);
-    // Should be able to write to it now.
-    BOOST_CHECK_EQUAL(DirIsWritable(tmpdirname), true);
-    fs::remove(tmpdirname);
-}
-
 BOOST_AUTO_TEST_CASE(test_ToLower)
 {
     BOOST_CHECK_EQUAL(ToLower('@'), '@');

src/util/fs_helpers.cpp

@@ -12,7 +12,6 @@
 #include <logging.h>
 #include <sync.h>
 #include <util/fs.h>
-#include <util/getuniquepath.h>
 #include <util/syserror.h>
 
 #include <cerrno>
@@ -51,31 +50,35 @@ static GlobalMutex cs_dir_locks;
  * is called.
  */
 static std::map<std::string, std::unique_ptr<fsbridge::FileLock>> dir_locks GUARDED_BY(cs_dir_locks);
-
-bool LockDirectory(const fs::path& directory, const fs::path& lockfile_name, bool probe_only)
+namespace util {
+LockResult LockDirectory(const fs::path& directory, const fs::path& lockfile_name, bool probe_only)
 {
     LOCK(cs_dir_locks);
     fs::path pathLockFile = directory / lockfile_name;
 
     // If a lock for this directory already exists in the map, don't try to re-lock it
     if (dir_locks.count(fs::PathToString(pathLockFile))) {
-        return true;
+        return LockResult::Success;
     }
 
     // Create empty lock file if it doesn't exist.
-    FILE* file = fsbridge::fopen(pathLockFile, "a");
-    if (file) fclose(file);
+    if (auto created{fsbridge::fopen(pathLockFile, "a")}) {
+        std::fclose(created);
+    } else {
+        return LockResult::ErrorWrite;
+    }
     auto lock = std::make_unique<fsbridge::FileLock>(pathLockFile);
     if (!lock->TryLock()) {
-        return error("Error while attempting to lock directory %s: %s", fs::PathToString(directory), lock->GetReason());
+        error("Error while attempting to lock directory %s: %s", fs::PathToString(directory), lock->GetReason());
+        return LockResult::ErrorLock;
     }
     if (!probe_only) {
         // Lock successful and we're not just probing, put it into the map
         dir_locks.emplace(fs::PathToString(pathLockFile), std::move(lock));
     }
-    return true;
+    return LockResult::Success;
 }
-
+} // namespace util
 void UnlockDirectory(const fs::path& directory, const fs::path& lockfile_name)
 {
     LOCK(cs_dir_locks);
@@ -88,19 +91,6 @@ void ReleaseDirectoryLocks()
     dir_locks.clear();
 }
 
-bool DirIsWritable(const fs::path& directory)
-{
-    fs::path tmpFile = GetUniquePath(directory);
-
-    FILE* file = fsbridge::fopen(tmpFile, "a");
-    if (!file) return false;
-
-    fclose(file);
-    remove(tmpFile);
-
-    return true;
-}
-
 bool CheckDiskSpace(const fs::path& dir, uint64_t additional_bytes)
 {
     constexpr uint64_t min_disk_space = 52428800; // 50 MiB

src/util/fs_helpers.h

@@ -35,9 +35,15 @@ void AllocateFileRange(FILE* file, unsigned int offset, unsigned int length);
  */
 [[nodiscard]] bool RenameOver(fs::path src, fs::path dest);
 
-bool LockDirectory(const fs::path& directory, const fs::path& lockfile_name, bool probe_only = false);
+namespace util {
+enum class LockResult {
+    Success,
+    ErrorWrite,
+    ErrorLock,
+};
+[[nodiscard]] LockResult LockDirectory(const fs::path& directory, const fs::path& lockfile_name, bool probe_only = false);
+} // namespace util
 void UnlockDirectory(const fs::path& directory, const fs::path& lockfile_name);
-bool DirIsWritable(const fs::path& directory);
 bool CheckDiskSpace(const fs::path& dir, uint64_t additional_bytes = 0);
 
 /** Get the size of a file by scanning it.

src/util/getuniquepath.cpp

@@ -1,14 +0,0 @@
-// Copyright (c) 2021-2022 The Bitcoin Core developers
-// Distributed under the MIT software license, see the accompanying
-// file COPYING or http://www.opensource.org/licenses/mit-license.php.
-
-#include <random.h>
-#include <util/fs.h>
-#include <util/strencodings.h>
-
-fs::path GetUniquePath(const fs::path& base)
-{
-    FastRandomContext rnd;
-    fs::path tmpFile = base / fs::u8path(HexStr(rnd.randbytes(8)));
-    return tmpFile;
-}

src/util/getuniquepath.h

@@ -1,19 +0,0 @@
-// Copyright (c) 2021 The Bitcoin Core developers
-// Distributed under the MIT software license, see the accompanying
-// file COPYING or http://www.opensource.org/licenses/mit-license.php.
-
-#ifndef BITCOIN_UTIL_GETUNIQUEPATH_H
-#define BITCOIN_UTIL_GETUNIQUEPATH_H
-
-#include <util/fs.h>
-
-/**
- * Helper function for getting a unique path
- *
- * @param[in] base  Base path
- * @returns base joined with a random 8-character long string.
- * @post Returned path is unique with high probability.
- */
-fs::path GetUniquePath(const fs::path& base);
-
-#endif // BITCOIN_UTIL_GETUNIQUEPATH_H

src/wallet/bdb.cpp

@@ -149,7 +149,7 @@ bool BerkeleyEnvironment::Open(bilingual_str& err)
 
     fs::path pathIn = fs::PathFromString(strPath);
     TryCreateDirectories(pathIn);
-    if (!LockDirectory(pathIn, ".walletlock")) {
+    if (util::LockDirectory(pathIn, ".walletlock") != util::LockResult::Success) {
         LogPrintf("Cannot obtain a lock on wallet directory %s. Another instance may be using it.\n", strPath);
         err = strprintf(_("Error initializing wallet database environment %s!"), fs::quoted(fs::PathToString(Directory())));
         return false;