On 26.06.2017 21:56, Mike Snitzer wrote: >> Interesting, I did *not* change to writethrough. However, there >> shouldn't have been any I/O on the device (it was not accessed by >> anything after I switched to the cleaner policy). [...] >> Anyways, I'll try to replicate my scenario again because I'm actually >> quite sure that I did everything correctly (I did it a few times). > > Except you didn't first switch to writethrough -- which is _not_ > correct. Absolutely, very good to know. So even without any I/O being request, dm-cache is allowed to "hold back" pages as long as the dm-cache device is in writeback mode? Would this also explain why the "dmsetup wait" hung indefinitely? I do think I followed a tutorial that I found on the net regarding this. Scary that such a crucial fact is missing there. The fact that dirty pages are reported as zero just gives the impression that everything is coherent, when in fact it's not. Regardless, I find this and your explanation extremely interesting and want to thank you for clearing this up. Very fascinating topic indeed. Best regards, Johannes -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
