Allow controlling mmap behavior through DatabaseOptions.

This also gets rid of the ability to disable mmap process-wide since
it's not needed and brittle global state.

Bug: 40144971
Change-Id: Id7dbb1537a88c7903bf9e2b68a70ba1e9d5b19c6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6239956
Reviewed-by: Etienne Bergeron <etienneb@chromium.org>
Reviewed-by: Anthony Vallée-Dubois <anthonyvd@chromium.org>
Reviewed-by: Tsuyoshi Horo <horo@chromium.org>
Commit-Queue: Olivier Li <olivierli@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1419443}

components/services/storage/shared_storage/shared_storage_database.cc

@@ -212,6 +212,9 @@ SharedStorageDatabase::SharedStorageDatabase(
     : db_(sql::DatabaseOptions()
               .set_wal_mode(base::FeatureList::IsEnabled(
                   blink::features::kSharedStorageAPIEnableWALForDatabase))
+              // Prevent SQLite from trying to use mmap, as SandboxedVfs does
+              // not currently support this.
+              .set_mmap_enabled(false)
               // We DCHECK that the page size is valid in the constructor for
               // `SharedStorageOptions`.
               .set_page_size(options->max_page_size)

components/services/storage/storage_service_impl.cc

@@ -78,12 +78,6 @@ void StorageServiceImpl::SetDataDirectory(
                           weak_ptr_factory_.GetWeakPtr()),
       base::SequencedTaskRunner::GetCurrentDefault()));
 
-  // Prevent SQLite from trying to use mmap, as SandboxedVfs does not currently
-  // support this.
-  //
-  // TODO(crbug.com/40144971): Configure this per Database instance.
-  sql::Database::DisableMmapByDefault();
-
   // SQLite needs our VFS implementation to work over a FilesystemProxy. This
   // installs it as the default implementation for the service process.
   sql::SandboxedVfs::Register(

sql/database.cc

@@ -77,8 +77,6 @@ namespace sql {
 
 namespace {
 
-bool enable_mmap_by_default_ = true;
-
 // The name of the main database associated with a sqlite3* connection.
 //
 // SQLite has the ability to ATTACH multiple databases to the same connection.
@@ -355,7 +353,7 @@ Database::Database(Database::Tag tag) : Database(DatabaseOptions{}, tag) {}
 
 Database::Database(DatabaseOptions options, Database::Tag tag)
     : options_(options),
-      mmap_disabled_(!enable_mmap_by_default_),
+      mmap_disabled_(!options.mmap_enabled_),
       histogram_tag_(tag.value),
       tracing_track_name_(base::StrCat({"Database: ", histogram_tag_})) {
   DCHECK_GE(options.page_size_, 512);
@@ -375,11 +373,6 @@ Database::~Database() {
   Close();
 }
 
-// static
-void Database::DisableMmapByDefault() {
-  enable_mmap_by_default_ = false;
-}
-
 bool Database::Open(const base::FilePath& path) {
   std::string path_string = AsUTF8ForSQL(path);
   TRACE_EVENT1("sql", "Database::Open", "path", path_string);

sql/database.h

@@ -248,6 +248,14 @@ struct COMPONENT_EXPORT(SQL) DatabaseOptions {
     return *this;
   }
 
+  // If true database attempts using memory mapped files. True by default. Only
+  // set to false when a condition is known that prevents the use of memory
+  // mapped files. See https://www.sqlite.org/mmap.html.
+  DatabaseOptions& set_mmap_enabled(bool mmap_enabled) {
+    mmap_enabled_ = mmap_enabled;
+    return *this;
+  }
+
  private:
   friend class Database;
   FRIEND_TEST_ALL_PREFIXES(DatabaseOptionsTest,
@@ -266,6 +274,7 @@ struct COMPONENT_EXPORT(SQL) DatabaseOptions {
   bool mmap_alt_status_discouraged_ = false;
   bool enable_views_discouraged_ = false;
   const char* vfs_name_discouraged_ = nullptr;
+  bool mmap_enabled_ = true;
 };
 
 // Holds database diagnostics in a structured format.
@@ -382,12 +391,6 @@ class COMPONENT_EXPORT(SQL) Database {
   Database& operator=(Database&&) = delete;
   ~Database();
 
-  // Allows mmapping to be disabled globally by default in the calling process.
-  // Must be called before any threads attempt to create a Database.
-  //
-  // TODO(crbug.com/40144971): Remove this global configuration.
-  static void DisableMmapByDefault();
-
   // Pre-init configuration ----------------------------------------------------
 
   // The page size that will be used when creating a new database.