On 7/2/20 4:28 AM, Huang, Ying wrote:
But, when the bit was removed (bit 0) the _other_ bit locations also got changed. That's not OK because the bit values are documented to mean one specific thing and users surely rely on them meaning that one thing and not changing from kernel to kernel. The end result is that if someone had a script that did:
sysctl vm.zone_reclaim_mode=1
That script went from doing nothing
Per my understanding, this script would have enabled node reclaim for clean unmapped pages before commit 648b5cf368e0 ("mm/vmscan: remove unused RECLAIM_OFF/RECLAIM_ZONE"). So we should revise the description here?
Yes, you're right. I updated the patch with the updated understanding about the implicit use of the bit but didn't update the changelog. I'll do that for v3.