On 12/7/2016 9:36 AM, David Miller wrote: [...]
What does the newer tool do on an older kernel if it doesn't see the fields? Does it check the size of the structure given back to it, and conditionally handle the older vs. the newer layout? It must do this.
Right but the rds-tool doesn't handle it well and needs to be fixed before this or any additional change in rds-info structures. To handle the kernel struct size issues with its user copy, there is a provision to probe kernel struct len and then decide on layout buts its not used/implemented in tools. The parsing comment I made is also not completely accurate. For now, I will drop this patch and submit it once the tools code is fixed along with other used fields to handle both layouts. I should have checked the full compatibility matrix as you commented. Sorry for oversight. Thanks for your comments Dave. Regard, Santosh