On Mon, Dec 7, 2020 at 1:34 PM Mike Galbraith [off-list ref] wrote:

On Mon, 2020-12-07 at 12:52 +0100, Vitaly Wool wrote:

quoted

Thanks. This trace beats me because I don't quite get how this could
have happened.

I swear there's a mythical creature loose in there somewhere ;-)
Everything looks just peachy up to the instant it goes boom, then you
find in the wreckage that which was most definitely NOT there just a
few ns ago.

quoted

Hitting write_unlock at line 341 would mean that HANDLES_ORPHANED bit
is set but obviously it isn't.
Could you please comment out the ".shrink = z3fold_zpool_shrink" line
and retry?

Unfortunately, that made zero difference.

Okay, I suggest that you submit the patch that changes read_lock() to
write_lock() in __release_z3fold_page() and I'll ack it then.
I would like to rewrite the code so that write_lock is not necessary
there but I don't want to hold you back and it isn't likely that I'll
complete this today.

Best regards,
   Vitaly