On 01/02/2013 04:45 PM, Nikos Chantziaras wrote: > On 02/01/13 22:49, Duane wrote: >> Qt 4.8 on Linux TinyCore or Fedora. >> >> I have a function to back up some files to a usb stick. I've had >> complaints from users that the files are sometime not copied. It looks >> like they're removing the usb stick before the standard sync cycle. If >> I call sync from my copy routine this works but it hangs the system >> waiting for sync to complete. >> >> If I mount the usb stick with -o sync, this also solves my problem but >> it also hangs the system. >> >> I have tried to use fsync on a per file basis but this doesn't solve my >> problem. I have a watchdog to maintain so I would need to use >> qApp->processEvents() periodically in busy loops. >> >> Does fsync not force the write to disk? Is there a way to sync only a >> particular folder? > > Once QFile::flush() is called, the data is sent to the OS. From there, > it's up to the system what to do with the data. Users need to unmount > the stick before removing it. If they don't want to do that, then they > need to set up their system such that it mounts the USB stick > synchronously by default. It's either that or unmount first. > > This is not a QFile problem. When someone removes a live filesystem > without unmounting it, loss of data is to be expected and should come as > no surprise. If you try to work around it, then you'll be hurting > performance for users who do know how to properly use their system > (calling QFile::sync() all the time can mess up buffering.)
This device is a "controller" with a touch screen and no access to a terminal where the user can enter anything. I would have to add something to the gui to unmount the device but I think this would be more or less the same as calling sync when the copying is done. _______________________________________________ Interest mailing list Interest@qt-project.org http://lists.qt-project.org/mailman/listinfo/interest
