On 8/22/18 8:27 AM, Jens Axboe wrote:

On 8/22/18 6:54 AM, Holger Hoffstätte wrote:

quoted

On 08/22/18 06:10, Jens Axboe wrote:

quoted

[...]
If you have time, please look at the 3 patches I posted earlier today.
Those are for mainline, so should be OK :-)

I'm just playing along at home but with those 3 I get repeatable
hangs & writeback not starting at all, but curiously *only* on my btrfs
device; for inexplicable reasons some other devices with ext4/xfs flush
properly. Yes, that surprised me too, but it's repeatable.
Now this may or may not have something to do with some of my in-testing
patches for btrfs itself, but if I remove those 3 wbt fixes, everything
is golden again. Not eager to repeat since it hangs sync & requires a
hard reboot.. :(
Just thought you'd like to know.

Thanks, that's very useful info! I'll see if I can reproduce that.

Any chance you can try with and see which patch is causing the issue?
I can't reproduce it here, seems solid.

Either that, or a reproducer would be great...

-- 
Jens Axboe