On Wed, 2021-07-21 at 19:54 +0100, David Howells wrote: > Jeff Layton <jlayton@xxxxxxxxxx> wrote: > > > The above two deltas seem like they should have been in patch #2. > > Yeah. Looks like at least partially so. > > > > @@ -635,15 +625,8 @@ void netfs_subreq_terminated(struct netfs_read_subrequest *subreq, > > > goto failed; > > > } > > > > > > - if (WARN(transferred_or_error > subreq->len - subreq->transferred, > > > - "Subreq overread: R%x[%x] %zd > %zu - %zu", > > > - rreq->debug_id, subreq->debug_index, > > > - transferred_or_error, subreq->len, subreq->transferred)) > > > - transferred_or_error = subreq->len - subreq->transferred; > > > - > > > subreq->error = 0; > > > - subreq->transferred += transferred_or_error; > > > - if (subreq->transferred < subreq->len) > > > + if (iov_iter_count(&subreq->iter)) > > > goto incomplete; > > > > > > > I must be missing it, but where does subreq->iter get advanced to the > > end of the current read? If you're getting rid of subreq->transferred > > then I think that has to happen above, no? > > For afs, afs_req_issue_op() points fsreq->iter at the subrequest iterator and > calls afs_fetch_data(). Thereafter, we wend our way to > afs_deliver_fs_fetch_data() or yfs_deliver_fs_fetch_data() which set > call->iter to point to that iterator and then call afs_extract_data() which > passes it to rxrpc_kernel_recv_data(), which eventually passes it to > skb_copy_datagram_iter(), which advances the iterator. > > For the cache, the subrequest iterator is passed to the cache backend by > netfs_read_from_cache(). This would be cachefiles_read() which calls > vfs_iocb_iter_read() which I thought advances the iterator (leastways, > filemap_read() keeps going until iov_iter_count() reaches 0 or some other stop > condition occurs and doesn't thereafter call iov_iter_revert()). > Ok, this will probably regress ceph then. We don't really have anything to do with the subreq->iter at this point and this patch doesn't change that. If you're going to make this change, it'd be cleaner to also fix up ceph_netfs_issue_op to advance the iter at the same time. -- Jeff Layton <jlayton@xxxxxxxxxx>
