Drop built-in atomicity support in favour of OverlayFS

src/build/adapter_filesystem.cc

@@ -77,8 +77,6 @@ auto BuildAdapterFilesystem::write_dependencies(
   this->refresh(path);
   const auto dependencies_path{this->dependencies_path(path)};
   std::filesystem::create_directories(dependencies_path.parent_path());
-  // To reset the inode and correctly handle hard links
-  std::filesystem::remove(dependencies_path);
   std::ofstream dependencies_stream{dependencies_path};
   assert(!dependencies_stream.fail());
   for (const auto &dependency : dependencies) {

src/index/generators.h

@@ -562,8 +562,6 @@ struct GENERATE_URITEMPLATE_ROUTES {
           const sourcemeta::one::BuildDynamicCallback<std::filesystem::path> &,
           const Context &router) -> void {
     std::filesystem::create_directories(destination.parent_path());
-    // To reset the inode and correctly handle hard links
-    std::filesystem::remove(destination);
     sourcemeta::core::URITemplateRouterView::save(router, destination);
   }
 };

src/index/index.cc

@@ -1,6 +1,5 @@
 #include <sourcemeta/blaze/linter.h>
 
-#include <sourcemeta/core/io.h>
 #include <sourcemeta/core/json.h>
 #include <sourcemeta/core/jsonschema.h>
 #include <sourcemeta/core/options.h>
@@ -24,7 +23,6 @@
 #include <cstdlib>     // EXIT_FAILURE, EXIT_SUCCESS
 #include <exception>   // std::exception
 #include <filesystem>  // std::filesystem
-#include <fstream>     // std::ofstream
 #include <iomanip>     // std::setw, std::setfill
 #include <iostream>    // std::cerr, std::cout
 #include <string>      // std::string
@@ -52,9 +50,6 @@
 // the resolver will not unescape it back when computing the relative path to an
 // entry
 constexpr auto SENTINEL{"%"};
-constexpr std::string_view STAGING_DIRECTORY{".sourcemeta-one-staging"};
-constexpr std::string_view STAGING_COMMITTED{
-    ".sourcemeta-one-staging-committed"};
 
 static auto attribute_not_disabled(
     const sourcemeta::one::Configuration::Collection &collection,
@@ -116,17 +111,17 @@ static auto index_main(const std::string_view &program,
   // (1) Parse the output directory
   /////////////////////////////////////////////////////////////////////////////
 
-  const auto final_output_path{
+  const auto output_path{
       std::filesystem::weakly_canonical(app.positional().at(1))};
 
-  if (std::filesystem::exists(final_output_path) &&
-      !std::filesystem::is_directory(final_output_path)) {
+  if (std::filesystem::exists(output_path) &&
+      !std::filesystem::is_directory(output_path)) {
     throw std::filesystem::filesystem_error{
-        "file already exists", final_output_path,
+        "file already exists", output_path,
         std::make_error_code(std::errc::file_exists)};
   }
 
-  std::cerr << "Writing output to: " << final_output_path.string() << "\n";
+  std::cerr << "Writing output to: " << output_path.string() << "\n";
 
   /////////////////////////////////////////////////////////////////////////////
   // (2) Process the configuration file
@@ -183,42 +178,10 @@ static auto index_main(const std::string_view &program,
   }
 
   /////////////////////////////////////////////////////////////////////////////
-  // (5) Prepare the output directory via staging for atomic commits
-  /////////////////////////////////////////////////////////////////////////////
-
-  // Place the staging directory as a sibling of the final output path to
-  // guarantee both reside on the same filesystem volume, which is required
-  // for the atomic rename to succeed
-  const auto staging_path{final_output_path.parent_path() /
-                          std::string{STAGING_DIRECTORY}};
-  // After an atomic swap, the staging directory already contains the previous
-  // committed output, so we can reuse it directly. However, if the process
-  // crashed mid-build, staging may be in a dirty state. We use a sentinel
-  // file to distinguish clean staging (from a completed swap) from dirty
-  // staging (from a crash). If dirty, we discard and re-bootstrap.
-  const auto staging_sentinel{final_output_path.parent_path() /
-                              std::string{STAGING_COMMITTED}};
-  if (std::filesystem::exists(staging_path) &&
-      !std::filesystem::exists(staging_sentinel)) {
-    std::cerr << "Discarding dirty staging directory\n";
-    std::filesystem::remove_all(staging_path);
-  }
-
-  if (!std::filesystem::exists(staging_path)) {
-    if (std::filesystem::exists(final_output_path)) {
-      std::cerr << "Hardlinking: " << final_output_path.string() << " => "
-                << staging_path.string() << "\n";
-      sourcemeta::core::hardlink_directory(final_output_path, staging_path);
-    } else {
-      std::filesystem::create_directories(staging_path);
-    }
-  }
-
-  // Remove the sentinel before building so that a crash leaves staging
-  // recognizable as dirty
-  std::filesystem::remove(staging_sentinel);
+  // (5) Prepare the output directory
+  /////////////////////////////////////////////////////////////////////////////
 
-  sourcemeta::one::Output output{staging_path};
+  sourcemeta::one::Output output{output_path};
 
   /////////////////////////////////////////////////////////////////////////////
   // (6) Store a mark of the One version for target dependencies
@@ -790,19 +753,6 @@ static auto index_main(const std::string_view &program,
 
   PROFILE_END(profiling, "Profile");
 
-  std::cerr << "Committing: " << staging_path.string() << " => "
-            << final_output_path.string() << "\n";
-  sourcemeta::core::atomic_directory_swap(final_output_path, staging_path);
-
-  // Mark the staging directory as clean so the next run knows it can be
-  // safely reused. On the very first run the swap is a plain rename and
-  // staging no longer exists, but writing the sentinel is still harmless
-  // because the next run will see no staging directory and bootstrap fresh.
-  std::ofstream sentinel_stream(staging_sentinel);
-  sentinel_stream.close();
-
-  PROFILE_END(profiling, "Commit");
-
   if (app.contains("time")) {
     for (const auto &entry : profiling.first) {
       std::cout << entry.second.count() << "ms " << entry.first << "\n";

src/index/output.h

@@ -8,6 +8,7 @@
 
 #include <cassert>       // assert
 #include <filesystem>    // std::filesystem
+#include <fstream>       // std::ofstream
 #include <shared_mutex>  // std::shared_mutex, std::shared_lock
 #include <unordered_map> // std::unordered_map
 
@@ -85,8 +86,6 @@ class Output {
       -> const std::filesystem::path & {
     assert(path.is_absolute());
     std::filesystem::create_directories(path.parent_path());
-    // To reset the inode and correctly handle hard links
-    std::filesystem::remove(path);
     std::ofstream stream{path};
     assert(!stream.fail());
     sourcemeta::core::stringify(document, stream);

src/shared/metapack.cc

@@ -57,8 +57,6 @@ auto write_stream(const std::filesystem::path &path,
     metadata.assign("extension", extension);
   }
 
-  // To reset the inode and correctly handle hard links
-  std::filesystem::remove(path);
   std::ofstream output{path};
   assert(!output.fail());
   sourcemeta::core::stringify(metadata, output);

test/cli/CMakeLists.txt

@@ -58,10 +58,6 @@ if(ONE_INDEX)
   sourcemeta_one_test_cli(common index non-existent-collection-directory)
   sourcemeta_one_test_cli(common index collection-path-is-file)
   sourcemeta_one_test_cli(common index deps-contents)
-  sourcemeta_one_test_cli(common index inode-reset-on-rebuild)
-  sourcemeta_one_test_cli(common index atomic-failure)
-  sourcemeta_one_test_cli(common index stale-staging-cleanup)
-  sourcemeta_one_test_cli(common index configuration-no-stale-cleanup)
   sourcemeta_one_test_cli(common index rebuild-zero-to-one)
   sourcemeta_one_test_cli(common index rebuild-one-to-zero)
   sourcemeta_one_test_cli(common index resolve-schema)

test/cli/index/common/comment-removed-on-rebuild.sh

@@ -35,7 +35,6 @@ Using configuration: $(realpath "$TMP")/one.json
 (  0%) Producing: explorer
 (100%) Producing: .
 (100%) Rendering: .
-Committing: $(realpath "$TMP")/.sourcemeta-one-staging => $(realpath "$TMP")/output
 EOF
 
 diff "$TMP/output.txt" "$TMP/expected.txt"
@@ -51,7 +50,6 @@ remove_threads_information "$TMP/output.txt"
 cat << EOF > "$TMP/expected.txt"
 Writing output to: $(realpath "$TMP")/output
 Using configuration: $(realpath "$TMP")/one.json
-Hardlinking: $(realpath "$TMP")/output => $(realpath "$TMP")/.sourcemeta-one-staging
 ( 50%) Reviewing: schemas
 (100%) Reviewing: schemas
 (  0%) Producing: explorer
@@ -61,7 +59,6 @@ Hardlinking: $(realpath "$TMP")/output => $(realpath "$TMP")/.sourcemeta-one-sta
 (skip) Rendering: . [index]
 (skip) Rendering: . [not-found]
 (skip) Producing: routes.bin [routes]
-Committing: $(realpath "$TMP")/.sourcemeta-one-staging => $(realpath "$TMP")/output
 EOF
 
 diff "$TMP/output.txt" "$TMP/expected.txt"

test/cli/index/common/comment-updated-on-rebuild.sh

@@ -35,7 +35,6 @@ Using configuration: $(realpath "$TMP")/one.json
 (  0%) Producing: explorer
 (100%) Producing: .
 (100%) Rendering: .
-Committing: $(realpath "$TMP")/.sourcemeta-one-staging => $(realpath "$TMP")/output
 EOF
 
 diff "$TMP/output.txt" "$TMP/expected.txt"
@@ -51,7 +50,6 @@ remove_threads_information "$TMP/output.txt"
 cat << EOF > "$TMP/expected.txt"
 Writing output to: $(realpath "$TMP")/output
 Using configuration: $(realpath "$TMP")/one.json
-Hardlinking: $(realpath "$TMP")/output => $(realpath "$TMP")/.sourcemeta-one-staging
 ( 50%) Reviewing: schemas
 (100%) Reviewing: schemas
 (  0%) Producing: explorer
@@ -61,7 +59,6 @@ Hardlinking: $(realpath "$TMP")/output => $(realpath "$TMP")/.sourcemeta-one-sta
 (skip) Rendering: . [index]
 (skip) Rendering: . [not-found]
 (skip) Producing: routes.bin [routes]
-Committing: $(realpath "$TMP")/.sourcemeta-one-staging => $(realpath "$TMP")/output
 EOF
 
 diff "$TMP/output.txt" "$TMP/expected.txt"