Disk cache: Add a method to cancel pending sparse operations.

The sparse IO methods require exclusive use of the cache entry
and they complain when that requirement is violated. When the
user cancels a request and reissues another one to the same entry,
we may be waiting for the previous operation to finish when we
receive a new IO request, so we fail.

This CL add a way for the HTTP cache to cancel IO operations and
get a notification when the disk cache is able to operate on that
entry again.

BUG=23862
TEST=unittests

Review URL: http://codereview.chromium.org/256090

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@28475 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 130 insertions, 8 deletions

diff --git a/net/http/http_cache.cc b/net/http/http_cache.cc
index 7fb9703..7985992 100644
--- a/net/http/http_cache.cc
+++ b/net/http/http_cache.cc
@@ -161,7 +161,10 @@ class HttpCache::Transaction : public HttpTransaction {
             network_read_callback_(this, &Transaction::OnNetworkReadCompleted)),
         ALLOW_THIS_IN_INITIALIZER_LIST(
             cache_read_callback_(new CancelableCompletionCallback<Transaction>(
-                this, &Transaction::OnCacheReadCompleted))) {
+                this, &Transaction::OnCacheReadCompleted))),
+        ALLOW_THIS_IN_INITIALIZER_LIST(
+            entry_ready_callback_(new CancelableCompletionCallback<Transaction>(
+                this, &Transaction::OnCacheEntryReady))) {
   }
 
   // Clean up the transaction.
@@ -251,6 +254,10 @@ class HttpCache::Transaction : public HttpTransaction {
   // a network error code.
   int BeginPartialCacheValidation();
 
+  // Validates the entry headers against the requested range and continues with
+  // the validation of the rest of the entry.  Returns a network error code.
+  int ValidateEntryHeadersAndContinue(bool byte_range_requested);
+
   // Performs the cache validation for the next chunk of data stored by the
   // cache.  If this chunk is not currently stored, starts the network request
   // to fetch it.  Returns a network error code.
@@ -345,6 +352,9 @@ class HttpCache::Transaction : public HttpTransaction {
   // Called to signal completion of the cache's ReadData method:
   void OnCacheReadCompleted(int result);
 
+  // Called to signal completion of the cache entry's ReadyForSparseIO method:
+  void OnCacheEntryReady(int result);
+
   scoped_refptr<LoadLog> load_log_;
   const HttpRequestInfo* request_;
   scoped_ptr<HttpRequestInfo> custom_request_;
@@ -373,14 +383,21 @@ class HttpCache::Transaction : public HttpTransaction {
   CompletionCallbackImpl<Transaction> network_read_callback_;
   scoped_refptr<CancelableCompletionCallback<Transaction> >
       cache_read_callback_;
+  scoped_refptr<CancelableCompletionCallback<Transaction> >
+      entry_ready_callback_;
 };
 
 HttpCache::Transaction::~Transaction() {
   if (cache_) {
     if (entry_) {
       bool cancel_request = reading_ && enable_range_support_;
-      if (cancel_request && !partial_.get())
-        cancel_request &= (response_.headers->response_code() == 200);
+      if (cancel_request) {
+        if (partial_.get()) {
+          entry_->disk_entry->CancelSparseIO();
+        } else {
+          cancel_request &= (response_.headers->response_code() == 200);
+        }
+      }
 
       cache_->DoneWithEntry(entry_, this, cancel_request);
     } else {
@@ -928,7 +945,10 @@ int HttpCache::Transaction::BeginPartialCacheValidation() {
     return BeginCacheValidation();
 
   bool byte_range_requested = partial_.get() != NULL;
-  if (!byte_range_requested) {
+  if (byte_range_requested) {
+    if (OK != entry_->disk_entry->ReadyForSparseIO(entry_ready_callback_))
+      return ERR_IO_PENDING;
+  } else {
     // The request is not for a range, but we have stored just ranges.
     partial_.reset(new PartialData());
     if (!custom_request_.get()) {
@@ -937,6 +957,13 @@ int HttpCache::Transaction::BeginPartialCacheValidation() {
     }
   }
 
+  return ValidateEntryHeadersAndContinue(byte_range_requested);
+}
+
+int HttpCache::Transaction::ValidateEntryHeadersAndContinue(
+    bool byte_range_requested) {
+  DCHECK(mode_ == READ_WRITE);
+
   if (!partial_->UpdateFromStoredHeaders(response_.headers, entry_->disk_entry,
                                          truncated_)) {
     // The stored data cannot be used. Get rid of it and restart this request.
@@ -1552,6 +1579,11 @@ void HttpCache::Transaction::OnCacheReadCompleted(int result) {
   DoCacheReadCompleted(result);
 }
 
+void HttpCache::Transaction::OnCacheEntryReady(int result) {
+  DCHECK_EQ(OK, result);
+  ValidateEntryHeadersAndContinue(true);
+}
+
 //-----------------------------------------------------------------------------
 
 HttpCache::HttpCache(HostResolver* host_resolver,
diff --git a/net/http/http_cache_unittest.cc b/net/http/http_cache_unittest.cc
index ea98c67..67d6de8 100644
--- a/net/http/http_cache_unittest.cc
+++ b/net/http/http_cache_unittest.cc
@@ -32,11 +32,13 @@ class MockDiskEntry : public disk_cache::Entry,
                       public base::RefCounted<MockDiskEntry> {
  public:
   MockDiskEntry()
-      : test_mode_(0), doomed_(false), sparse_(false), fail_requests_(false) {
+      : test_mode_(0), doomed_(false), sparse_(false), fail_requests_(false),
+        busy_(false), delayed_(false) {
   }
 
   explicit MockDiskEntry(const std::string& key)
-      : key_(key), doomed_(false), sparse_(false), fail_requests_(false) {
+      : key_(key), doomed_(false), sparse_(false), fail_requests_(false),
+        busy_(false), delayed_(false) {
     //
     // 'key' is prefixed with an identifier if it corresponds to a cached POST.
     // Skip past that to locate the actual URL.
@@ -131,7 +133,7 @@ class MockDiskEntry : public disk_cache::Entry,
 
   virtual int ReadSparseData(int64 offset, net::IOBuffer* buf, int buf_len,
                              net::CompletionCallback* completion_callback) {
-    if (!sparse_)
+    if (!sparse_ || busy_)
       return net::ERR_CACHE_OPERATION_NOT_SUPPORTED;
     if (offset < 0)
       return net::ERR_FAILED;
@@ -152,11 +154,15 @@ class MockDiskEntry : public disk_cache::Entry,
       return num;
 
     CallbackLater(completion_callback, num);
+    busy_ = true;
+    delayed_ = false;
     return net::ERR_IO_PENDING;
   }
 
   virtual int WriteSparseData(int64 offset, net::IOBuffer* buf, int buf_len,
                               net::CompletionCallback* completion_callback) {
+    if (busy_)
+      return net::ERR_CACHE_OPERATION_NOT_SUPPORTED;
     if (!sparse_) {
       if (data_[1].size())
         return net::ERR_CACHE_OPERATION_NOT_SUPPORTED;
@@ -181,7 +187,7 @@ class MockDiskEntry : public disk_cache::Entry,
   }
 
   virtual int GetAvailableRange(int64 offset, int len, int64* start) {
-    if (!sparse_)
+    if (!sparse_ || busy_)
       return net::ERR_CACHE_OPERATION_NOT_SUPPORTED;
     if (offset < 0)
       return net::ERR_FAILED;
@@ -212,6 +218,23 @@ class MockDiskEntry : public disk_cache::Entry,
     return count;
   }
 
+  virtual void CancelSparseIO() { cancel_ = true; }
+
+  virtual int ReadyForSparseIO(net::CompletionCallback* completion_callback) {
+    if (!cancel_)
+      return net::OK;
+
+    cancel_ = false;
+    DCHECK(completion_callback);
+    if (test_mode_ & TEST_MODE_SYNC_CACHE_READ)
+      return net::OK;
+
+    // The pending operation is already in the message loop (and hopefuly
+    // already in the second pass).  Just notify the caller that it finished.
+    CallbackLater(completion_callback, 0);
+    return net::ERR_IO_PENDING;
+  }
+
   // Fail most subsequent requests.
   void set_fail_requests() { fail_requests_ = true; }
 
@@ -224,6 +247,21 @@ class MockDiskEntry : public disk_cache::Entry,
         &MockDiskEntry::RunCallback, callback, result));
   }
   void RunCallback(net::CompletionCallback* callback, int result) {
+    if (busy_) {
+      // This is kind of hacky, but controlling the behavior of just this entry
+      // from a test is sort of complicated.  What we really want to do is
+      // delay the delivery of a sparse IO operation a little more so that the
+      // request start operation (async) will finish without seeing the end of
+      // this operation (already posted to the message loop)... and without
+      // just delaying for n mS (which may cause trouble with slow bots).  So
+      // we re-post this operation (all async sparse IO operations will take two
+      // trips trhough the message loop instead of one).
+      if (!delayed_) {
+        delayed_ = true;
+        return CallbackLater(callback, result);
+      }
+    }
+    busy_ = false;
     callback->Run(result);
   }
 
@@ -233,8 +271,14 @@ class MockDiskEntry : public disk_cache::Entry,
   bool doomed_;
   bool sparse_;
   bool fail_requests_;
+  bool busy_;
+  bool delayed_;
+  static bool cancel_;
 };
 
+// Static.
+bool MockDiskEntry::cancel_ = false;
+
 class MockDiskCache : public disk_cache::Backend {
  public:
   MockDiskCache()
@@ -2344,6 +2388,52 @@ TEST(HttpCache, RangeGET_Cancel) {
   RemoveMockTransaction(&kRangeGET_TransactionOK);
 }
 
+// Tests that we don't delete a sparse entry when we start a new request after
+// cancelling the previous one.
+TEST(HttpCache, RangeGET_Cancel2) {
+  MockHttpCache cache;
+  cache.http_cache()->set_enable_range_support(true);
+  AddMockTransaction(&kRangeGET_TransactionOK);
+
+  RunTransactionTest(cache.http_cache(), kRangeGET_TransactionOK);
+  MockHttpRequest request(kRangeGET_TransactionOK);
+
+  Context* c = new Context();
+  int rv = cache.http_cache()->CreateTransaction(&c->trans);
+  EXPECT_EQ(net::OK, rv);
+
+  rv = c->trans->Start(&request, &c->callback, NULL);
+  if (rv == net::ERR_IO_PENDING)
+    rv = c->callback.WaitForResult();
+
+  EXPECT_EQ(2, cache.network_layer()->transaction_count());
+  EXPECT_EQ(1, cache.disk_cache()->open_count());
+  EXPECT_EQ(1, cache.disk_cache()->create_count());
+
+  // Make sure that we revalidate the entry and read from the cache (a single
+  // read will return while waiting for the network).
+  scoped_refptr<net::IOBufferWithSize> buf = new net::IOBufferWithSize(5);
+  rv = c->trans->Read(buf, buf->size(), &c->callback);
+  EXPECT_EQ(net::ERR_IO_PENDING, rv);
+  rv = c->callback.WaitForResult();
+  rv = c->trans->Read(buf, buf->size(), &c->callback);
+  EXPECT_EQ(net::ERR_IO_PENDING, rv);
+
+  // Destroy the transaction before completing the read.
+  delete c;
+
+  // We have the read and the delete (OnProcessPendingQueue) waiting on the
+  // message loop. This means that a new transaction will just reuse the same
+  // active entry (no open or create).
+
+  RunTransactionTest(cache.http_cache(), kRangeGET_TransactionOK);
+
+  EXPECT_EQ(3, cache.network_layer()->transaction_count());
+  EXPECT_EQ(1, cache.disk_cache()->open_count());
+  EXPECT_EQ(1, cache.disk_cache()->create_count());
+  RemoveMockTransaction(&kRangeGET_TransactionOK);
+}
+
 #ifdef NDEBUG
 // This test hits a NOTREACHED so it is a release mode only test.
 TEST(HttpCache, RangeGET_OK_LoadOnlyFromCache) {