avoid deadlock: cancel hydration requests coming from itself

our current infrastructure will cause a deadlock for any hydration
requests coming from desktop files client itself

the main thread is responsible for executing the hydration request but
if the same thread is already blocked waiting for the hydration to
happen, both (open system call and hydration request handling) process
will never be completed and wait for each over in a stuck cycle

Signed-off-by: Matthieu Gallien <matthieu.gallien@nextcloud.com>

diff --git a/src/libsync/vfs/cfapi/cfapiwrapper.cpp b/src/libsync/vfs/cfapi/cfapiwrapper.cpp
index 5ff32c64d3c88b2f95fbe02abd78b4051b8c86a9..bbbf3f0d950469a03bd91028ec92b82aa64f7c29 100644 (file)
--- a/src/libsync/vfs/cfapi/cfapiwrapper.cpp
+++ b/src/libsync/vfs/cfapi/cfapiwrapper.cpp
@@ -157,6 +157,12 @@ void CALLBACK cfApiFetchDataCallback(const CF_CALLBACK_INFO *callbackInfo, const
                               callbackInfo->FileSize.QuadPart);
     };
 
+    if (QCoreApplication::applicationPid() == callbackInfo->ProcessInfo->ProcessId) {
+        qCCritical(lcCfApiWrapper) << "implicit hydration triggered by the client itself. Will lead to a deadlock. Cancel";
+        sendTransferError();
+        return;
+    }
+
     auto vfs = reinterpret_cast<OCC::VfsCfApi *>(callbackInfo->CallbackContext);
     Q_ASSERT(vfs->metaObject()->className() == QByteArrayLiteral("OCC::VfsCfApi"));
     const auto path = QString(QString::fromWCharArray(callbackInfo->VolumeDosName) + QString::fromWCharArray(callbackInfo->NormalizedPath));