On 8/4/26 10:01 AM, Christoph Hellwig wrote: 
> On Sun, Aug 02, 2026 at 07:14:26AM -0400, Tal Zussman wrote:
>> To reproduce, on a device with a sub-page block size, write a known
>> pattern with O_DIRECT, mmap the same range, store to it, msync() and
>> fsync(), then read it back with O_DIRECT. A reproducer is available at
> 
> Heh, shared mmap writes to block devices..
> 
>> [1].
>> 
>> [1] https://urldefense.com/v3/__https://gist.github.com/ 
> tzussman/18ab05cba4b3fdc79cce0a69d1fd05b4__;!!BDUfV1Et5lrpZQ! 
> U2LXFwSk7d0ux5nR34lhpiqhUc75GwdbKoKfJ3Q99AlXZf6q-4Zu4abOqvcnW4gx6nBiH5895_e5MpFV$ <https://urldefense.com/v3/__https://gist.github.com/tzussman/18ab05cba4b3fdc79cce0a69d1fd05b4__;!!BDUfV1Et5lrpZQ!U2LXFwSk7d0ux5nR34lhpiqhUc75GwdbKoKfJ3Q99AlXZf6q-4Zu4abOqvcnW4gx6nBiH5895_e5MpFV$>
> 
> Can you submit this to blktests?

Done: https://github.com/linux-blktests/blktests/pull/258

> 
> Looks good:
> 
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> 

Thanks!