On 18 Apr 2015, at 17:36, Doug Ledford <dledford at redhat.com> wrote: > On Sat, 2015-04-18 at 15:09 +0100, Justin Clift wrote: >> On 18 Apr 2015, at 10:39, Bart Van Assche <bart.vanassche at sandisk.com> wrote: >>> On 03/11/15 18:01, Justin Clift wrote: >>>> On 10 Mar 2015, at 11:09, Bart Van Assche <bart.vanassche at sandisk.com> wrote: >>>>> Hello, >>>>> >>>>> Sorry but I will not be able to attend this meeting because at that time I will be on a plane. But I have been thinking further about how to provide SCST RPMs for CentOS. How about using the approach documented on http://wiki.centos.org/HowTos/BuildingKernelModules (weak updates) and taking the risk that the IB drivers may break if an update introduces an RDMA ABI change ? >>>> >>>> The "take a risk X might break" bit doesn't really sound suitable >>>> for the CentOS audience. >>>> >>>> That being said... how often does the RDMA ABI change? If it's >>>> once every X years, then it might be live-able (with sufficient >>>> catches/warning so users aren't affected). >>> >>> (back from traveling - sorry for the delay in replying) >>> >>> Hello Justin, >>> >>> So far I have only seen the RDMA ABI change between RHEL releases (e.g. from 7.0 to 7.1) but not yet due to a kernel update. Which of course is no guarantee that a change of the RDMA API will never happen in the future between kernel releases ... >> >> Hmmmm... in general RHEL has an attitude of "don't change ABI in >> updates", > > It's not an attitude, it's a hard requirement that requires managerial > approval for an exception to break it. > >> but RDMA may or may not have different assumptions. I >> have no idea. ;) > > It does. We exempt the kernel portion of the RDMA stack from any ABI > claims entirely. For user space, we make a best effort to preserve > backward binary compatibility, but not forward. Meaning if you compile > a user space app against 7.0, our 7.1 and later updates will all be > backward compatible to your compiled program. However, we add > extensions, so if you compile against 7.2 let's say, and use one of the > new extensions, then you program will not run on 7.0. However, keep in > mind that this is a best effort. On occasion, with managerial approval, > we break this too. The RDMA simply moves too fast to keep it static > through the life of a RHEL product. Thanks Doug. :) + Justin -- GlusterFS - http://www.gluster.org An open source, distributed file system scaling to several petabytes, and handling thousands of clients. My personal twitter: twitter.com/realjustinclift