DB:Open should fail on tmpfs when use_direct_reads=true

Summary:
Before:

> $ TEST_TMPDIR=/dev/shm ./db_bench -use_direct_reads=true -benchmarks=readrandomwriterandom -num=10000000 -reads=100000 -write_buffer_size=1048576 -target_file_size_base=1048576 -max_bytes_for_level_base=4194304 -max_background_jobs=12 -readwritepercent=50 -key_size=16 -value_size=48 -threads=32
DB path: [/dev/shm/dbbench]
put error: IO error: While open a file for random read: /dev/shm/dbbench/000007.sst: Invalid argument
put error: IO error: While open a file for random read: /dev/shm/dbbench/000007.sst: Invalid argument
put error: IO error: While open a file for random read: /dev/shm/dbbench/000007.sst: Invalid argument
put error: IO error: While open a file for random read: /dev/shm/dbbench/000007.sst: Invalid argument
put error: IO error: While open a file for random read: /dev/shm/dbbench/000007.sst: Invalid argument
put error: IO error: While open a file for random read: /dev/shm/dbbench/000007.sst: Invalid argument
put error: IO error: While open a file for random read: /dev/shm/dbbench/000007.sst: Invalid argument
put error: IO error: While open a file for random read: /dev/shm/dbbench/000007.sst: Invalid argument
put error: IO error: While open a file for random read: /dev/shm/dbbench/000007.sst: Invalid argument
db_bench: tpp.c:84: __pthread_tpp_change_priority: Assertion `new_prio == -1 || (new_prio >= fifo_min_prio && new_prio <= fifo_max_prio)' failed.
put error: IO error: While open a file for random read: /dev/shm/dbbench/000007.sst: Invalid argument
put error: IO error: While open a file for random read: /dev/shm/dbbench/000007.sst: Invalid argument

After:
> TEST_TMPDIR=/dev/shm ./db_bench -use_direct_reads=true -benchmarks=readrandomwriterandom -num=10000000 -reads=100000 -write_buffer_size=1048576 -target_file_size_base=1048576 -max_bytes_for_level_base=4194304 -max_background_jobs=12 -readwritepercent=50 -key_size=16 -value_size=48 -threads=32
Initializing RocksDB Options from the specified file
Initializing RocksDB Options from command-line flags
open error: Not implemented: Direct I/O is not supported by the specified DB.
Closes https://github.com/facebook/rocksdb/pull/3539

Differential Revision: D7082658

Pulled By: miasantreble

fbshipit-source-id: f9d9c6ec3b5e9e049cab52154940ee101ba4d342

db/db_impl_open.cc

@@ -356,6 +356,29 @@ Status DBImpl::Recover(
       assert(s.IsIOError());
       return s;
     }
+    // Verify compatibility of env_options_ and filesystem
+    {
+      unique_ptr<RandomAccessFile> idfile;
+      EnvOptions customized_env(env_options_);
+      customized_env.use_direct_reads |=
+          immutable_db_options_.use_direct_io_for_flush_and_compaction;
+      s = env_->NewRandomAccessFile(IdentityFileName(dbname_), &idfile,
+                                    customized_env);
+      if (!s.ok()) {
+        const char* error_msg = s.ToString().c_str();
+        // Check if unsupported Direct I/O is the root cause
+        customized_env.use_direct_reads = false;
+        s = env_->NewRandomAccessFile(IdentityFileName(dbname_), &idfile,
+                                      customized_env);
+        if (s.ok()) {
+          return Status::InvalidArgument(
+              "Direct I/O is not supported by the specified DB.");
+        } else {
+          return Status::InvalidArgument(
+              "Found options incompatible with filesystem", error_msg);
+        }
+      }
+    }
   }
 
   Status s = versions_->Recover(column_families, read_only);