From 0a97125ec07f72c0dc0dd11d21327be070a03536 Mon Sep 17 00:00:00 2001
From: Levi Tamasi <ltamasi@fb.com>
Date: Wed, 14 Aug 2019 16:07:03 -0700
Subject: [PATCH] Fix data races in BlobDB (#5698)

Summary:
Some accesses to blob_files_ and open_ttl_files_ in BlobDBImpl, as well
as to expiration_range_ in BlobFile were not properly synchronized.
The patch fixes this and also makes sure the invariant that obsolete_files_
is a subset of blob_files_ holds even when an attempt to delete an obsolete
blob file fails.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5698

Test Plan:
COMPILE_WITH_TSAN=1 make blob_db_test
gtest-parallel --repeat=1000 ./blob_db_test --gtest_filter="*ShutdownWait*"

The test fails with TSAN errors ~20 times out of 1000 without the patch but
completes successfully 1000 out of 1000 times with the fix.

Differential Revision: D16793235

Pulled By: ltamasi

fbshipit-source-id: 8034b987598d4fdc9f15098d4589cc49cde484e9
---
 utilities/blob_db/blob_db_impl.cc | 27 ++++++++++++++++++++++++---
 1 file changed, 24 insertions(+), 3 deletions(-)

diff --git a/utilities/blob_db/blob_db_impl.cc b/utilities/blob_db/blob_db_impl.cc
index 86501280d..8088e4273 100644
--- a/utilities/blob_db/blob_db_impl.cc
+++ b/utilities/blob_db/blob_db_impl.cc
@@ -724,6 +724,7 @@ Status BlobDBImpl::PutBlobValue(const WriteOptions& /*options*/,
     }
     if (s.ok()) {
       if (expiration != kNoExpiration) {
+        WriteLock file_lock(&blob_file->mutex_);
         blob_file->ExtendExpirationRange(expiration);
       }
       s = CloseBlobFileIfNeeded(blob_file);
@@ -1177,6 +1178,8 @@ std::pair<bool, int64_t> BlobDBImpl::SanityCheck(bool aborted) {
     return std::make_pair(false, -1);
   }
 
+  ReadLock rl(&mutex_);
+
   ROCKS_LOG_INFO(db_options_.info_log, "Starting Sanity Check");
   ROCKS_LOG_INFO(db_options_.info_log, "Number of files %" ROCKSDB_PRIszt,
                  blob_files_.size());
@@ -1198,7 +1201,13 @@ std::pair<bool, int64_t> BlobDBImpl::SanityCheck(bool aborted) {
                        blob_file->BlobFileNumber(), blob_file->GetFileSize(),
                        blob_file->BlobCount(), blob_file->Immutable());
     if (blob_file->HasTTL()) {
-      auto expiration_range = blob_file->GetExpirationRange();
+      ExpirationRange expiration_range;
+
+      {
+        ReadLock file_lock(&blob_file->mutex_);
+        expiration_range = blob_file->GetExpirationRange();
+      }
+
       pos += snprintf(buf + pos, sizeof(buf) - pos,
                       ", expiration range (%" PRIu64 ", %" PRIu64 ")",
                       expiration_range.first, expiration_range.second);
@@ -1501,7 +1510,14 @@ Status BlobDBImpl::GCFileAndUpdateLSM(const std::shared_ptr<BlobFile>& bfptr,
   // this reads the key but skips the blob
   Reader::ReadLevel shallow = Reader::kReadHeaderKey;
 
-  bool file_expired = has_ttl && now >= bfptr->GetExpirationRange().second;
+  ExpirationRange expiration_range;
+
+  {
+    ReadLock file_lock(&bfptr->mutex_);
+    expiration_range = bfptr->GetExpirationRange();
+  }
+
+  bool file_expired = has_ttl && now >= expiration_range.second;
 
   if (!file_expired) {
     // read the blob because you have to write it back to new file
@@ -1761,7 +1777,11 @@ std::pair<bool, int64_t> BlobDBImpl::DeleteObsoleteFiles(bool aborted) {
                    "Will delete file due to snapshot success %s",
                    bfile->PathName().c_str());
 
-    blob_files_.erase(bfile->BlobFileNumber());
+    {
+      WriteLock wl(&mutex_);
+      blob_files_.erase(bfile->BlobFileNumber());
+    }
+
     Status s = DeleteDBFile(&(db_impl_->immutable_db_options()),
                             bfile->PathName(), blob_dir_, true,
                             /*force_fg=*/false);
@@ -1794,6 +1814,7 @@ std::pair<bool, int64_t> BlobDBImpl::DeleteObsoleteFiles(bool aborted) {
   if (!tobsolete.empty()) {
     WriteLock wl(&mutex_);
     for (auto bfile : tobsolete) {
+      blob_files_.insert(std::make_pair(bfile->BlobFileNumber(), bfile));
       obsolete_files_.push_front(bfile);
     }
   }