DBImpl::GetWalPreallocateBlockSize() should return size_t

Summary: WritableFile::SetPreallocationBlockSize() requires parameter as size_t, and options used in DBImpl::GetWalPreallocateBlockSize() are all size_t. WritableFile::SetPreallocationBlockSize() should return size_t to avoid build break if size_t is not uint64_t.

Test Plan: Run existing tests.

Reviewers: andrewkr, IslamAbdelRahman, yiwu

Reviewed By: yiwu

Subscribers: leveldb, andrewkr, dhruba

Differential Revision: https://reviews.facebook.net/D64137

db/db_impl.cc

@@ -3682,8 +3682,8 @@ bool DBImpl::MCOverlap(ManualCompaction* m, ManualCompaction* m1) {
   return true;
 }
 
-uint64_t DBImpl::GetWalPreallocateBlockSize(uint64_t write_buffer_size) const {
-  uint64_t bsize = write_buffer_size / 10 + write_buffer_size;
+size_t DBImpl::GetWalPreallocateBlockSize(uint64_t write_buffer_size) const {
+  size_t bsize = write_buffer_size / 10 + write_buffer_size;
   // Some users might set very high write_buffer_size and rely on
   // max_total_wal_size or other parameters to control the WAL size.
   if (db_options_.max_total_wal_size > 0) {

db/db_impl.h

@@ -1068,7 +1068,7 @@ class DBImpl : public DB {
   bool HaveManualCompaction(ColumnFamilyData* cfd);
   bool MCOverlap(ManualCompaction* m, ManualCompaction* m1);
 
-  uint64_t GetWalPreallocateBlockSize(uint64_t write_buffer_size) const;
+  size_t GetWalPreallocateBlockSize(uint64_t write_buffer_size) const;
 };
 
 // Sanitize db options.  The caller should delete result.info_log if