store: use ImmediateFuture in ObjectStore::getBlobSha1

Summary:
This allows the ImmediateFuture to be used as is in FileInode::getSha1 to
reduce the transition from folly::Future to ImmediateFuture

Reviewed By: chadaustin, kmancini

Differential Revision: D31667901

fbshipit-source-id: 3985e256d3c29c334d7e542ea8a2ce4e89528773

eden/fs/inodes/DeferredDiffEntry.cpp

@@ -249,10 +249,15 @@ class ModifiedBlobDiffEntry : public DeferredDiffEntry {
         currentBlobHash_{currentBlobHash} {}
 
   folly::Future<folly::Unit> run() override {
-    auto f1 = context_->store->getBlobSha1(
-        scmEntry_.getHash(), context_->getFetchContext());
-    auto f2 = context_->store->getBlobSha1(
-        currentBlobHash_, context_->getFetchContext());
+    auto f1 =
+        context_->store
+            ->getBlobSha1(scmEntry_.getHash(), context_->getFetchContext())
+            .semi()
+            .via(&folly::QueuedImmediateExecutor::instance());
+    auto f2 = context_->store
+                  ->getBlobSha1(currentBlobHash_, context_->getFetchContext())
+                  .semi()
+                  .via(&folly::QueuedImmediateExecutor::instance());
     return collectSafe(f1, f2).thenValue(
         [this](const std::tuple<Hash20, Hash20>& info) {
           const auto& [info1, info2] = info;

eden/fs/inodes/FileInode.cpp

@@ -597,7 +597,11 @@ folly::Future<bool> FileInode::isSameAs(
   auto f1 = getSha1(fetchContext)
                 .semi()
                 .via(&folly::QueuedImmediateExecutor::instance());
-  auto f2 = getMount()->getObjectStore()->getBlobSha1(blobID, fetchContext);
+  auto f2 = getMount()
+                ->getObjectStore()
+                ->getBlobSha1(blobID, fetchContext)
+                .semi()
+                .via(&folly::QueuedImmediateExecutor::instance());
   return folly::collectUnsafe(f1, f2).thenTry(
       [](folly::Try<std::tuple<Hash20, Hash20>>&& try_) {
         if (try_.hasException()) {
@@ -692,9 +696,8 @@ ImmediateFuture<Hash20> FileInode::getSha1(ObjectFetchContext& fetchContext) {
     case State::BLOB_NOT_LOADING:
     case State::BLOB_LOADING:
       // If a file is not materialized, it should have a hash value.
-      return getObjectStore()
-          ->getBlobSha1(state->nonMaterializedState->hash, fetchContext)
-          .semi();
+      return getObjectStore()->getBlobSha1(
+          state->nonMaterializedState->hash, fetchContext);
     case State::MATERIALIZED_IN_OVERLAY:
 #ifdef _WIN32
       return makeImmediateFutureWith(
@@ -1084,7 +1087,7 @@ void FileInode::materializeNow(
       state->nonMaterializedState->hash, *context);
   std::optional<Hash20> blobSha1;
   if (blobSha1Future.isReady()) {
-    blobSha1 = blobSha1Future.value();
+    blobSha1 = std::move(blobSha1Future).get();
   }
 
   getOverlayFileAccess(state)->createFile(getNodeId(), *blob, blobSha1);

eden/fs/store/Diff.cpp

@@ -560,10 +560,18 @@ void processBothPresent(
                                    entryPath = currentPath + scmEntry.getName(),
                                    &scmEntry,
                                    &wdEntry] {
-              auto scmFuture = context->store->getBlobSha1(
-                  scmEntry.getHash(), context->getFetchContext());
-              auto wdFuture = context->store->getBlobSha1(
-                  wdEntry.getHash(), context->getFetchContext());
+              auto scmFuture =
+                  context->store
+                      ->getBlobSha1(
+                          scmEntry.getHash(), context->getFetchContext())
+                      .semi()
+                      .via(&folly::QueuedImmediateExecutor::instance());
+              auto wdFuture =
+                  context->store
+                      ->getBlobSha1(
+                          wdEntry.getHash(), context->getFetchContext())
+                      .semi()
+                      .via(&folly::QueuedImmediateExecutor::instance());
               return collectSafe(scmFuture, wdFuture)
                   .thenValue([entryPath = entryPath.copy(),
                               context](const std::tuple<Hash20, Hash20>& info) {

eden/fs/store/ObjectStore.cpp

@@ -314,11 +314,12 @@ Future<BlobMetadata> ObjectStore::getBlobMetadata(
       });
 }
 
-Future<Hash20> ObjectStore::getBlobSha1(
+ImmediateFuture<Hash20> ObjectStore::getBlobSha1(
     const ObjectId& id,
     ObjectFetchContext& context) const {
   return getBlobMetadata(id, context)
-      .thenValue([](const BlobMetadata& metadata) { return metadata.sha1; });
+      .thenValue([](const BlobMetadata& metadata) { return metadata.sha1; })
+      .semi();
 }
 
 Future<uint64_t> ObjectStore::getBlobSize(

eden/fs/store/ObjectStore.h

@@ -186,7 +186,7 @@ class ObjectStore : public IObjectStore,
   /**
    * Returns the SHA-1 hash of the contents of the blob with the given ID.
    */
-  folly::Future<Hash20> getBlobSha1(
+  ImmediateFuture<Hash20> getBlobSha1(
       const ObjectId& id,
       ObjectFetchContext& context) const;