On Mon, Nov 23, 2020 at 11:42:46AM -0500, Olga Kornievskaia wrote: > Hi Frank, Chuck, > > I would like your option on how LISTXATTR is supposed to work over > RDMA. Here's my current understanding of why the listxattr is not > working over the RDMA. > > This happens when the listxattr is called with a very small buffer > size which RDMA wants to send an inline request. I really dont > understand why, Chuck, you are not seeing any problems with hardware > as far as I can tell it would have the same problem because the inline > threshold size would still make this size inline. > rcprdma_inline_fixup() is trying to write to pages that don't exist. > > When LISTXATTR sets this flag XDRBUF_SPARSE_PAGES there is code that > will allocate pages in xs_alloc_sparse_pages() but this is ONLY for > TCP. RDMA doesn't have anything like that. > > Question: Should there be code added to RDMA that will do something > similar when it sees that flag set? Or, should LISTXATTR be re-written > to be like READDIR which allocates pages before calling the code. Hm.. so if the flag never worked for RDMA, was NFS_V3_ACL ever tested over RDMA? That's the only other user. If the flag simply doesn't work, I agree that it should either be fixed or just removed. It wouldn't be the end of the world to change LISTXATTRS (and GETXATTR) to use preallocated pages. But, I didn't do that because I didn't want to waste the max size (64k) every time, even though you usually just get a few hundred bytes at most. So it seems like fixing XDRBUF_SPARSE_PAGES is cleaner. - Frank
