Support overlapping operations on the SimpleEntryImpl.

net/disk_cache/simple/simple_entry_impl.cc

Index: net/disk_cache/simple/simple_entry_impl.cc
diff --git a/net/disk_cache/simple/simple_entry_impl.cc b/net/disk_cache/simple/simple_entry_impl.cc
index 1917a88715091ac1a37be9dae3b8fd104b6f4edf..7d2de7a76a99a767740c95f445d202980ef289fd 100644
--- a/net/disk_cache/simple/simple_entry_impl.cc
+++ b/net/disk_cache/simple/simple_entry_impl.cc
@@ -88,6 +88,7 @@ int SimpleEntryImpl::DoomEntry(WeakPtr<SimpleIndex> index,
 
 void SimpleEntryImpl::Doom() {
   DCHECK(io_thread_checker_.CalledOnValidThread());
+  DCHECK(!operation_running_);
 #if defined(OS_POSIX)
   // This call to static SimpleEntryImpl::DoomEntry() will just erase the
   // underlying files. On POSIX, this is fine; the files are still open on the
@@ -101,12 +102,22 @@ void SimpleEntryImpl::Doom() {
 
 void SimpleEntryImpl::Close() {
   DCHECK(io_thread_checker_.CalledOnValidThread());
-  if (!synchronous_entry_in_use_by_worker_) {
-    WorkerPool::PostTask(FROM_HERE,
-                         base::Bind(&SimpleSynchronousEntry::Close,
-                                    base::Unretained(synchronous_entry_)),
-                         true);
+  if (operation_running_) {

[gavinp, 2013/04/17 11:04:36]

I think if you rebase on top of https://codereview.chromium.org/13880016/ , then
this won't be necessary at all; Close() will just be safe to run.

Do you think it's a good idea to rebase this on top of that CL, and continue?

[felipeg, 2013/04/17 11:51:22]

If I am going to land before you, I think I should keep it this way and you
merge and fix.

Even with your CL, I still think it makes sense to run the Close operation in
the end of the queue.
Although I know your CL solves that problem and allows Close to run at any time,
but for the sake of consistency with the idea of a queue of operations, we
should run close as the last operation in the queue.

Also
I think your CL will not be able to CHECK(HasOneRef()) anymore, since we can
have multiple Closures enqueued to run later, holding a pointer to |this|.

[gavinp, 2013/04/17 13:13:45]

Agreed. And whoever wins the race dodges the merge. Fair point.
With my CL, it runs last always, as it's launched from the destructor! So, I
agree.
Yeah. Those checks sure didn't live long.

+    // Postpone close operation.
+    // Push the close operation to the end of the line. This way we run all
+    // operations before we are able close.
+    operations_.push(
+        base::Bind(&SimpleEntryImpl::Close,
+                   weak_ptr_factory_.GetWeakPtr()));
+    return;
   }
+  DCHECK(operations_.size() == 0);
+  DCHECK(!operation_running_);
+
+  WorkerPool::PostTask(FROM_HERE,
+                       base::Bind(&SimpleSynchronousEntry::Close,
+                                  base::Unretained(synchronous_entry_)),
+                       true);
   // Entry::Close() is expected to release this entry. See disk_cache.h for
   // details.
   delete this;
@@ -138,15 +149,32 @@ int SimpleEntryImpl::ReadData(int index,
                               int buf_len,
                               const CompletionCallback& callback) {
   DCHECK(io_thread_checker_.CalledOnValidThread());
-  // TODO(gavinp): Add support for overlapping reads. The net::HttpCache does
-  // make overlapping read requests when multiple transactions access the same
-  // entry as read only. This might make calling SimpleSynchronousEntry::Close()
-  // correctly more tricky (see SimpleEntryImpl::EntryOperationComplete).
-  if (synchronous_entry_in_use_by_worker_) {
-    NOTIMPLEMENTED();
-    CHECK(false);
-  }
-  synchronous_entry_in_use_by_worker_ = true;
+  if (index < 0 || index >= kSimpleEntryFileCount || buf_len < 0)
+    return net::ERR_INVALID_ARGUMENT;
+  if (offset >= data_size_[index] || offset < 0 || !buf_len)
+    return 0;
+  // TODO(felipeg): Optimization: Add support for truly parallel read
+  // operations.
+  operations_.push(
+      base::Bind(&SimpleEntryImpl::ReadDataInternal,
+                 weak_ptr_factory_.GetWeakPtr(),
+                 index,
+                 offset,
+                 make_scoped_refptr(buf),
+                 buf_len,
+                 callback));
+  RunNextOperationIfNeeded();
+  return net::ERR_IO_PENDING;
+}
+
+void SimpleEntryImpl::ReadDataInternal(int index,

[gavinp, 2013/04/17 11:04:36]

Method ordering: this should go to the end of the file.

[felipeg, 2013/04/17 11:51:22]

Done.

+                                       int offset,
+                                       scoped_refptr<net::IOBuffer> buf,
+                                       int buf_len,
+                                       const CompletionCallback& callback) {
+  DCHECK(io_thread_checker_.CalledOnValidThread());
+  DCHECK(!operation_running_);
+  operation_running_ = true;
   if (index_)
     index_->UseIfExists(key_);
   SynchronousOperationCallback sync_operation_callback =
@@ -156,10 +184,9 @@ int SimpleEntryImpl::ReadData(int index,
   WorkerPool::PostTask(FROM_HERE,
                        base::Bind(&SimpleSynchronousEntry::ReadData,
                                   base::Unretained(synchronous_entry_),
-                                  index, offset, make_scoped_refptr(buf),
+                                  index, offset, buf,
                                   buf_len, sync_operation_callback),
                        true);
-  return net::ERR_IO_PENDING;
 }
 
 int SimpleEntryImpl::WriteData(int index,
@@ -169,13 +196,41 @@ int SimpleEntryImpl::WriteData(int index,
                                const CompletionCallback& callback,
                                bool truncate) {
   DCHECK(io_thread_checker_.CalledOnValidThread());
-  if (synchronous_entry_in_use_by_worker_) {
-    NOTIMPLEMENTED();
-    CHECK(false);
-  }
-  synchronous_entry_in_use_by_worker_ = true;
+  if (index < 0 || index >= kSimpleEntryFileCount || offset < 0 || buf_len < 0)
+    return net::ERR_INVALID_ARGUMENT;
+
+  operations_.push(
+      base::Bind(&SimpleEntryImpl::WriteDataInternal,
+                 weak_ptr_factory_.GetWeakPtr(),
+                 index,
+                 offset,
+                 make_scoped_refptr(buf),
+                 buf_len,
+                 callback,
+                 truncate));
+  RunNextOperationIfNeeded();
+
+  // TODO(felipeg): Optimization: Add support for optimistic writes, quickly
+  // returning net::OK here.
+  return net::ERR_IO_PENDING;
+}
+
+void SimpleEntryImpl::WriteDataInternal(int index,
+                                       int offset,
+                                       scoped_refptr<net::IOBuffer> buf,
+                                       int buf_len,
+                                       const CompletionCallback& callback,
+                                       bool truncate) {
+  DCHECK(io_thread_checker_.CalledOnValidThread());
+  DCHECK(!operation_running_);
+  operation_running_ = true;
   if (index_)
     index_->UseIfExists(key_);
+
+  last_used_ = base::Time::Now();
+  last_modified_ = base::Time::Now();
+  data_size_[index] = buf_len;
+
   SynchronousOperationCallback sync_operation_callback =
       base::Bind(&SimpleEntryImpl::EntryOperationComplete,
                  index_, callback, weak_ptr_factory_.GetWeakPtr(),
@@ -183,10 +238,9 @@ int SimpleEntryImpl::WriteData(int index,
   WorkerPool::PostTask(FROM_HERE,
                        base::Bind(&SimpleSynchronousEntry::WriteData,
                                   base::Unretained(synchronous_entry_),
-                                  index, offset, make_scoped_refptr(buf),
+                                  index, offset, buf,
                                   buf_len, sync_operation_callback, truncate),
                        true);
-  return net::ERR_IO_PENDING;
 }
 
 int SimpleEntryImpl::ReadSparseData(int64 offset,
@@ -245,7 +299,7 @@ SimpleEntryImpl::SimpleEntryImpl(
       path_(synchronous_entry->path()),
       key_(synchronous_entry->key()),
       synchronous_entry_(synchronous_entry),
-      synchronous_entry_in_use_by_worker_(false),
+      operation_running_(false),
       index_(index) {
   DCHECK(synchronous_entry);
   SetSynchronousData();
@@ -291,9 +345,10 @@ void SimpleEntryImpl::EntryOperationComplete(
   }
 
   if (entry) {
-    DCHECK(entry->synchronous_entry_in_use_by_worker_);
-    entry->synchronous_entry_in_use_by_worker_ = false;
+    DCHECK(entry->operation_running_);
+    entry->operation_running_ = false;
     entry->SetSynchronousData();
+    entry->RunNextOperationIfNeeded();
   } else {
     // |entry| must have had Close() called while this operation was in flight.
     // Since the simple cache now only supports one pending entry operation in
@@ -306,9 +361,19 @@ void SimpleEntryImpl::EntryOperationComplete(
   completion_callback.Run(result);
 }
 
+bool SimpleEntryImpl::RunNextOperationIfNeeded() {
+  DCHECK(io_thread_checker_.CalledOnValidThread());
+  if (operations_.size() <= 0 || operation_running_)
+    return false;
+  base::Closure operation = operations_.front();
+  operations_.pop();
+  operation.Run();
+  return true;
+}
+
 void SimpleEntryImpl::SetSynchronousData() {
   DCHECK(io_thread_checker_.CalledOnValidThread());
-  DCHECK(!synchronous_entry_in_use_by_worker_);
+  DCHECK(!operation_running_);
   // TODO(felipeg): These copies to avoid data races are not optimal. While
   // adding an IO thread index (for fast misses etc...), we can store this data
   // in that structure. This also solves problems with last_used() on ext4