search for: nbd_aio_is_readi

The code for (eg) nbd_aio_pread starts by checking this outside the lock: if (!(nbd_aio_is_ready (h) || nbd_aio_is_processing (h))) { However there can still be a race condition even though h->state is atomic: Thread A Thread B (in a call that holds h->lock) (calling nbd_aio_pread) --------------------------------------------------------------------

Since Eric's improvements to the command queue in commit 6af72b8 (and following) there's now a queue of commands waiting to be issued stored in the handle, and there's no need to issue commands only from the ready state. We can therefore remove the want_to_send logic, queue as many commands as possible, and don't need to test if the socket is ready for POLLOUT. This commit also

Patch 1/6 was posted before and I didn't change it: https://www.redhat.com/archives/libguestfs/2019-May/thread.html#00134 That doesn't necessarily mean I shouldn't change it, I'm posting it again because the other patches depend on it. The main change in this series is we add three new API functions: nbd_aio_is_created - connection has just been created

Rich recently patched things to generate one man page per function rather than libnbd-api.3 (nice), but in doing so got stumped by a problem with a fresh git clone (automake fails for any 'include' directive that does not already exist). I've figured out how to hack around it, but the hack requires GNU make. We already use GNU make constructs elsewhere (such as $(wildcard)), but

On 6/4/19 6:23 AM, Richard W.M. Jones wrote: > The code for (eg) nbd_aio_pread starts by checking this outside > the lock: > > if (!(nbd_aio_is_ready (h) || nbd_aio_is_processing (h))) { > > However there can still be a race condition even though h->state is > atomic: > > Thread A Thread B > (in a call that holds h->lock)

On 6/5/19 6:15 AM, Richard W.M. Jones wrote: > For each nbd_(unlocked_)?aio_is_* function, split it into an internal > function that tests the state and a public visible API function. > > For calls within the library, use the internal function. > > This is simple refactoring. > > As a side effect this fixes a race condition identified by Eric Blake: > > Thread A

Similar to the recent --mask-handshake command line added to nbdkit to test client fallbacks to crippled servers, it can be worth testing server fallbacks to crippled clients. And just as we have exposed whether the client will request structured replies, we can also expose whether the client will understand various handshake flags from the NBD protocol. Of course, we default to supporting all

For each nbd_(unlocked_)?aio_is_* function, split it into an internal function that tests the state and a public visible API function. For calls within the library, use the internal function. This is simple refactoring. As a side effect this fixes a race condition identified by Eric Blake: Thread A Thread B (in a call that holds h->lock) (calling nbd_aio_pread)

This allows us to connect directly to a connected socket. How exactly the socket is created and connected to the NBD server is left up to the main program. The only real complexity in this patch is allowing file descriptors to be passed to libnbd APIs. Luckily in C and Python we can treat them exactly as integers, and in OCaml they are also integers but with a different type. ---

This works. I'm in the middle of testing whether there is any noticable benefit. Rich.

This is slightly redundant with just trying nbd_set_tls(nbd, 2) then checking for failure; however, this function does not set errors and looks more similar to nbd_supports_uri. --- This is borderline enough that I figured I'd post it to check if we want it. generator/generator | 45 ++++++++++++++++++++++++++++++++++++++------- interop/interop.c | 4 ++++ lib/handle.c | 12

--- .gitignore | 1 + examples/Makefile.am | 12 + examples/concurrent-writer.c | 450 +++++++++++++++++++++++++++ examples/threaded-reads-and-writes.c | 2 +- 4 files changed, 464 insertions(+), 1 deletion(-) diff --git a/.gitignore b/.gitignore index 30438c1..e4dad91 100644 --- a/.gitignore +++ b/.gitignore @@ -41,6 +41,7 @@ Makefile.in

For commands with long names and/or short descriptors, you can end up going over 72 characters in the first line of the man page (causing podwrapper to complain). Wrap these lines. --- generator/generator | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/generator/generator b/generator/generator index 7d3f656..ad1cb6b 100755 --- a/generator/generator +++ b/generator/generator

This adds new APIs for running a local NBD server and connecting to it using systemd socket activation (instead of stdin/stdout). This includes interop tests against nbdkit and qemu-nbd which I believe are the only NBD servers supporting socket activation. (If we find others then we can add more interop tests in future.) The upstream spec for systemd socket activation is here:

v1: https://www.redhat.com/archives/libguestfs/2019-June/msg00014.html I pushed a few bits which are uncontroversial. The main changes since v1 are: An extra patch removes the want_to_send / check for nbd_aio_is_ready in examples/threaded-reads-and-writes.c. This logic was wrong since commit 6af72b87 as was pointed out by Eric in his review. Comments and structure of

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

I need to think about this patch series a bit more, but it does at least pass the tests. Rich.

Automake insists that any file present in a Makefile.am 'include' must be present, but it has no idea about the GNU make extension 'sinclude'. Use this to our advantage: as long as Makefile.inc has nothing other than variable modifications (done in the previous patch), and our rules properly generate it when needed (thanks to generator_built), then running 'make' will

On 8/11/20 12:12 PM, Richard W.M. Jones wrote: > I think this needs extra documentation in docs/libnbd.pod because it's > definitely not clear just from the rather thin manual page for > set_opt_mode how it works. docs/libnbd.pod is a good place for a > broader description of how it works. Yes, good idea. State-wise, the existing flow was: Created - Progress only by command

This works, but there's no time saving and I'm still investigating whether it does what I think it does. Nevertheless I thought I would post it because it (probably) implements the idea I had last night outlined in: https://www.redhat.com/archives/libguestfs/2019-June/msg00010.html The meat of the change is patch 4. Patch 5 is an example which I would probably fold into patch 4 for