On Thu, Dec 12, 2024 at 12:58:26PM +0900, Sergey Senozhatsky wrote:

Hi,

We've got two reports [1] [2] (could be the same person) which
suggest that ext4 may change page content while the page is under
write().  The particular problem here the case when ext4 is on
the zram device.  zram compresses every page written to it, so if
the page content can be modified concurrently with zram's compression
then we can't really use zram with ext4.

This smells like ext4 doesn't respect BDI_CAP_STABLE_WRITES somewhere.