> On Nov 23, 2020, at 11:42 AM, Olga Kornievskaia <olga.kornievskaia@xxxxxxxxx> 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? Isn't the logic in rpcrdma_convert_iovs() allocating those pages? > Or, should LISTXATTR be re-written > to be like READDIR which allocates pages before calling the code. AIUI READDIR reads into the directory inode's page cache. I recall that Frank couldn't do that for LISTXATTR because there's no similar page cache associated with the xattr listing. That said, I would prefer that the *XATTR procedures directly allocate pages instead of relying on SPARSE_PAGES, which is a hack IMO. I think it would have to use alloc_page() for that, and then ensure those pages are released when the call has completed. I'm not convinced this is the cause of the problem you're seeing, though. -- Chuck Lever
