On 01/02/2013 06:08 PM, Lincoln Ramsay wrote: > On 03/01/13 06:49, Duane wrote: >> I have a function to back up some files to a usb stick. > > Using a variant of the FAT filesystem no doubt? > >> 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. > > USB sticks are quite slow so it can take quite a while to complete a > 'sync' operation. You could popup a message "Please wait for the copy to > complete" before calling sync (though you've got to ensure it's visible > before the system hangs)... > >> I have tried to use fsync on a per file basis but this doesn't solve my >> problem. > > This _should_ work but perhaps not on whatever filesystem the USB stick > uses (or perhaps you're using it wrong?). I guess sync is able to > complete (from what you've described). >
I'm using QFile::copy(source,target). I've tried changing it to use the non static copy from QFile but I don't have a pointer to the target. So I create another instance of QFile for that one and call fsync on it after the copy but this doesn't work. >> Does fsync not force the write to disk? Is there a way to sync only a >> particular folder? > > You could try manually copying the data yourself. Open the source file > and the destination file. Use the O_SYNC flag and non-blocking IO > operations so that you can keep your UI responsive while the copying > completes. More work but may get you the results you want (and you can > have an accurate progress bar as well). This is what I'm thinking of doing. I think that this way, fsync may also work. But it was much simpler to just use QFile::copy(). _______________________________________________ Interest mailing list Interest@qt-project.org http://lists.qt-project.org/mailman/listinfo/interest
