On Tue, Apr 9, 2019 at 12:01 AM Antonio SJ Musumeci <trapexit@spawn.link> wrote:
>
> I had a user of my FUSE based filesystem report corruption while using
> an app which used mmap for file IO on a Raspberry Pi 3B. Files would
> be corrupted only if greater than 4GB. I replicated the behavior with
> a simple test app[0] on a RPi2 using the latest Raspbian (Linux
> raspberrypi 4.14.98-v7+ #1200 SMP Tue Feb 12 20:27:48 GMT 2019 armv7l
> GNU/Linux) and i686 Debian 9 in a VM (Linux debian 4.9.0-8-686 #1 SMP
> Debian 4.9.144-3.1 (2019-02-19) i686 GNU/Linux).
>
> What appears to happen is that after the offset reaches (st_size &
> 0xFFFFFFFF) bytes the FUSE server no longer receives write requests
> for modified pages. If the file size is exactly 4GB it won't ever
> receive a write. Reads still come in for all addresses and there are
> no errors on the client's side.

Hi,

Thanks for the report.

The attached patch almost certainly should fix this, but I've not
tested due to the extra effort needed for 32bit kernel testing.

If you can easily test it, than that would be good, otherwise I'll
just queue the patch as being obviously correct and likely fixing the
bug as well.

Thanks,
Miklos