Re: [Libguestfs] [libnbd PATCH 2/2] poll: Improve our interface

Make nbd_poll slightly more like poll(), allowing a user to detect timeouts by returning 0 on timeout and 1 when we made progress. It turns out that none of our internal uses ever expect a timeout (we only call nbd_internal_poll with timeout==-1 because we expect a reply from the server), but the public function might as well be nicer. Also handle POLLERR (server closed its read end, so our writes will fail) and POLLNVAL (the fd itself is closed) as outright errors, and POLLHUP the same as POLLIN (the server closed its write end, so read() will eventually see EOF even if we have to drain a buffer first). Perhaps we also want to add an nbd_aio_notify_err() that can inform the machine of any externally-detected error on the fd to the server, where the poll loop invokes that on POLLERR, and where we tweak the generator to permit that external event in any other public state. But that's a bigger patch. --- generator/generator | 18 +++++++++++++----- lib/poll.c | 13 ++++++++++--- 2 files changed, 23 insertions(+), 8 deletions(-)

+++ b/lib/poll.c @@ -57,21 +57,28 @@ nbd_unlocked_poll (struct nbd_handle *h, int timeout) set_error (errno, "poll"); return -1; }