On Sat, Aug 30, 2025 at 01:38:50PM -0400, Mike Snitzer wrote: > Hi Chuck, > > Hopeful these 2 patches more clearly demonstrate what I'm finding > needed when using RDMA with my NFSD misaligned DIO READ patch. > > These patches build ontop of my v8 patchset. I've included quite a lot > of context for the data mismatch seen by the NFS client, etc in the > patch headers. > > If I'm understanding you correctly, next step is to look closer at the > rpcrdma code that would skip the throwaway front-pad page from being > mapped to the start of the RDMA READ payload returned to the NFS > client? > > Such important adjustment code would need to know that the rq_bvec[] > that reflects the READ payload doesn't include a bvec that points to > the first page of rqstp->rq_pages (pointed to by rqstp->rq_next_page > on entry to nfsd_iter_read) -- so it must skip past that memory in > the READ payload's RDMA memory returned to NFS client? > > Thanks, > Mike > > Mike Snitzer (2): > NFSD: fix misaligned DIO READ to not use a start_extra_page, exposes rpcrdma bug? > NFSD: use /end/ of rq_pages for front_pad page, simpler workaround for rpcrdma bug > > fs/nfsd/vfs.c | 27 ++++++++------------------- > 1 file changed, 8 insertions(+), 19 deletions(-) > > -- > 2.44.0 > Another important detail to mention, I've been working ontop of a 6.12.24 stable baseline that I've backported all NFS and NFSD changes through 6.17-rc1 + (slightly stale) nfsd-testing to, please see: https://git.kernel.org/pub/scm/linux/kernel/git/snitzer/linux.git/log/?h=kernel-6.12.24/nfsd-testing-snitm.18-testing Not sure if rebasing to the latest nfsd-testing would show this issue... I'm thinking yes, but cannot say for sure. Needing the ability to test/develop Hammerspace and pNFS stuff has prevented me from simply rebasing. But it should be doable without too much effort. Mike
