Pass through use_fs_buffer to Read method (facebook#13200)

Summary:
This is a follow up to facebook#13177, which was supposed to disable the file system buffer optimization for compaction reads. However, it did not work as expected because I did not pass through `use_fs_buffer` to the `Read` method, which also calls `UseFSBuffer`.

Pull Request resolved: facebook#13200

Test Plan:
I added simple tests to verify we do not hit the overflow issue when we are doing compaction prefetches.

```
 ./prefetch_test --gtest_filter="*FSBufferPrefetchForCompaction*"
```

Of course I will be looking through the warm storage crash test logs as well once the change is merged.

Reviewed By: anand1976

Differential Revision: D66996079

Pulled By: archang19

fbshipit-source-id: b4d9254f1354ccfc53a307174de5f2388b7e5474

file/file_prefetch_buffer.cc

@@ -93,11 +93,10 @@ void FilePrefetchBuffer::PrepareBufferForRead(
 Status FilePrefetchBuffer::Read(BufferInfo* buf, const IOOptions& opts,
                                 RandomAccessFileReader* reader,
                                 uint64_t read_len, uint64_t aligned_useful_len,
-                                uint64_t start_offset) {
+                                uint64_t start_offset, bool use_fs_buffer) {
   Slice result;
   Status s;
   char* to_buf = nullptr;
-  bool use_fs_buffer = UseFSBuffer(reader);
   if (use_fs_buffer) {
     s = FSBufferDirectRead(reader, buf, opts, start_offset + aligned_useful_len,
                            read_len, result);
@@ -197,12 +196,14 @@ Status FilePrefetchBuffer::Prefetch(const IOOptions& opts,
 
   Status s;
   if (read_len > 0) {
-    s = Read(buf, opts, reader, read_len, aligned_useful_len, rounddown_offset);
+    s = Read(buf, opts, reader, read_len, aligned_useful_len, rounddown_offset,
+             use_fs_buffer);
   }
 
   if (usage_ == FilePrefetchBufferUsage::kTableOpenPrefetchTail && s.ok()) {
     RecordInHistogram(stats_, TABLE_OPEN_PREFETCH_TAIL_READ_BYTES, read_len);
   }
+  assert(buf->offset_ <= offset);
   return s;
 }
 
@@ -733,7 +734,8 @@ Status FilePrefetchBuffer::PrefetchInternal(const IOOptions& opts,
   }
 
   if (read_len1 > 0) {
-    s = Read(buf, opts, reader, read_len1, aligned_useful_len1, start_offset1);
+    s = Read(buf, opts, reader, read_len1, aligned_useful_len1, start_offset1,
+             use_fs_buffer);
     if (!s.ok()) {
       AbortAllIOs();
       FreeAllBuffers();
@@ -861,6 +863,7 @@ bool FilePrefetchBuffer::TryReadFromCacheUntracked(
   if (copy_to_overlap_buffer) {
     buf = overlap_buf_;
   }
+  assert(buf->offset_ <= offset);
   uint64_t offset_in_buffer = offset - buf->offset_;
   *result = Slice(buf->buffer_.BufferStart() + offset_in_buffer, n);
   if (prefetched) {

file/file_prefetch_buffer.h

@@ -430,7 +430,8 @@ class FilePrefetchBuffer {
 
   Status Read(BufferInfo* buf, const IOOptions& opts,
               RandomAccessFileReader* reader, uint64_t read_len,
-              uint64_t aligned_useful_len, uint64_t start_offset);
+              uint64_t aligned_useful_len, uint64_t start_offset,
+              bool use_fs_buffer);
 
   Status ReadAsync(BufferInfo* buf, const IOOptions& opts,
                    RandomAccessFileReader* reader, uint64_t read_len,

file/prefetch_test.cc

@@ -3710,6 +3710,62 @@ TEST_P(FSBufferPrefetchTest, FSBufferPrefetchUnalignedReads) {
   }
 }
 
+TEST_P(FSBufferPrefetchTest, FSBufferPrefetchForCompaction) {
+  // Quick test to make sure file system buffer reuse is disabled for compaction
+  // reads. Will update once it is re-enabled
+  // Primarily making sure we do not hit unsigned integer overflow issues
+  std::string fname = "fs-buffer-prefetch-for-compaction";
+  Random rand(0);
+  std::string content = rand.RandomString(32768);
+  Write(fname, content);
+
+  FileOptions opts;
+  std::unique_ptr<RandomAccessFileReader> r;
+  Read(fname, opts, &r);
+
+  std::shared_ptr<Statistics> stats = CreateDBStatistics();
+  ReadaheadParams readahead_params;
+  readahead_params.initial_readahead_size = 8192;
+  readahead_params.max_readahead_size = 8192;
+  bool use_async_prefetch = GetParam();
+  // Async IO is not enabled for compaction prefetching
+  if (use_async_prefetch) {
+    return;
+  }
+  readahead_params.num_buffers = 1;
+
+  FilePrefetchBuffer fpb(readahead_params, true, false, fs(), clock(),
+                         stats.get());
+
+  Slice result;
+  Status s;
+  ASSERT_TRUE(
+      fpb.TryReadFromCache(IOOptions(), r.get(), 0, 4096, &result, &s, true));
+  ASSERT_EQ(s, Status::OK());
+  ASSERT_EQ(strncmp(result.data(), content.substr(0, 4096).c_str(), 4096), 0);
+
+  fpb.UpdateReadPattern(4096, 4096, false);
+
+  ASSERT_TRUE(fpb.TryReadFromCache(IOOptions(), r.get(), 8192, 8192, &result,
+                                   &s, true));
+  ASSERT_EQ(s, Status::OK());
+  ASSERT_EQ(strncmp(result.data(), content.substr(8192, 8192).c_str(), 8192),
+            0);
+
+  ASSERT_TRUE(fpb.TryReadFromCache(IOOptions(), r.get(), 12288, 4096, &result,
+                                   &s, true));
+  ASSERT_EQ(s, Status::OK());
+  ASSERT_EQ(strncmp(result.data(), content.substr(12288, 4096).c_str(), 4096),
+            0);
+
+  // Read from 16000-26000 (start and end do not meet normal alignment)
+  ASSERT_TRUE(fpb.TryReadFromCache(IOOptions(), r.get(), 16000, 10000, &result,
+                                   &s, true));
+  ASSERT_EQ(s, Status::OK());
+  ASSERT_EQ(strncmp(result.data(), content.substr(16000, 10000).c_str(), 10000),
+            0);
+}
+
 }  // namespace ROCKSDB_NAMESPACE
 
 int main(int argc, char** argv) {