search for: nbd_aio_is_ready

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) -------------------------------------------------------------------- h-...

...+ * the same buffer for multiple in-flight requests. It doesn't + * matter here because we're just trying to write random stuff, + * but that would be Very Bad in a real application. */ - want_to_send = - i > 0 && in_flight < MAX_IN_FLIGHT && nbd_aio_is_ready (nbd); + while (i > 0 && in_flight < MAX_IN_FLIGHT) { + offset = rand () % (exportsize - sizeof buf); + cmd = rand () & 1; + if (cmd == 0) + handle = nbd_aio_pwrite (nbd, buf, sizeof buf, offset, 0); + else + handle = nbd_aio_pread (nbd, buf, s...

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) (calling nbd_aio_pread) > --------------------------------------...

...tified by Eric Blake: > > Thread A Thread B > (in a call that holds h->lock) (calling nbd_aio_pread) > -------------------------------------------------------------------- > h->state is processing > checks nbd_aio_is_ready > (it's false) > h->state is moved to READY > checks nbd_aio_is_processing > (it's false) > validation check fails > > (...

...t;\ +Return the state of the handshake flags on this handle. When the +handle has not yet completed a connection (see C<nbd_aio_is_created>), +this returns the flags that the client is willing to use, provided +the server also advertises those flags. After the connection is +ready (see C<nbd_aio_is_ready>), this returns the flags that were +actually agreed on between the server and client. If the NBD +protocol defines new handshake flags, then the return value from +a newer library version may include bits that were undefined at +the time of compilation."; + see_also = ["L<nbd_s...

...is fixes a race condition identified by Eric Blake: Thread A Thread B (in a call that holds h->lock) (calling nbd_aio_pread) -------------------------------------------------------------------- h->state is processing checks nbd_aio_is_ready (it's false) h->state is moved to READY checks nbd_aio_is_processing (it's false) validation check fails (However the state was valid so the...

...BD server listening on C<hostname:port>. Parameters behave as documented in L<nbd_connect_tcp(3)>. +You can check if the connection is still connecting by calling +L<nbd_aio_is_connecting(3)>, or if it has connected to the server +and completed the NBD handshake by calling L<nbd_aio_is_ready(3)>, +on the connection."; + }; + + "aio_connect_socket", { + default_call with + args = [ Fd "sock" ]; ret = RErr; + permitted_states = [ Created ]; + shortdesc = "connect directly to a connected socket"; + longdesc = "\ +Begin connecting...

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

...C<nbd_supports_uri>. Support for +URIs that require TLS will fail if libnbd was not compiled with +gnutls; you can test whether this is the case with C<nbd_supports_tls>."; }; "connect_unix", { @@ -1497,7 +1517,9 @@ and completed the NBD handshake by calling C<nbd_aio_is_ready>, on the connection. This call will fail if libnbd was not compiled with libxml2; you can -test whether this is the case with C<nbd_supports_uri>."; +test whether this is the case with C<nbd_supports_uri>. Support for +URIs that require TLS will fail if libnbd was not compil...

...;i); + goto error; + } + + /* Do we want to send another request and there's room to issue it + * and the connection is in the READY state so it can be used to + * issue a request. + */ + want_to_send = + i > 0 && in_flight < MAX_IN_FLIGHT && nbd_aio_is_ready (nbd); + + fds[0].fd = nbd_aio_get_fd (nbd); + fds[0].events = want_to_send ? POLLOUT : 0; + fds[0].revents = 0; + + dir = nbd_aio_get_direction (nbd); + if ((dir & LIBNBD_AIO_DIRECTION_WRITE) != 0) { + /* The concurrent writer is always writable, we don't have to +...

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

...egin connecting to it over stdin/stdout. Parameters behave as documented in L<nbd_connect_command(3)>. +You can check if the connection is still connecting by calling +L<nbd_aio_is_connecting(3)>, or if it has connected to the server +and completed the NBD handshake by calling L<nbd_aio_is_ready(3)>, +on the connection."; + }; + + "aio_connect_socket_activation", { + default_call with + args = [ StringList "argv" ]; ret = RErr; + permitted_states = [ Created ]; + shortdesc = "connect using systemd socket activation"; + longdesc = &quot...

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 examples/concurrent-writes.c has been updated to match. Callbacks now return int instead of void. In some cases we ignore this return value. I...

...xt to read from the server. If using L<poll(2)> you would set C<events = POLLIN>. If C<revents> returns C<POLLIN> -you would then call C<nbd_aio_notify_read>. +or C<POLLHUP> you would then call C<nbd_aio_notify_read>. Note that once libnbd reaches C<nbd_aio_is_ready>, this direction is returned even before a command is issued via C<nbd_aio_pwrite> and diff --git a/lib/poll.c b/lib/poll.c index 982b172..d356afe 100644 --- a/lib/poll.c +++ b/lib/poll.c @@ -57,21 +57,28 @@ nbd_unlocked_poll (struct nbd_handle *h, int timeout) set_error (errno, &quo...

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

...read_structured \ - nbd_aio_pwrite \ - nbd_aio_disconnect \ - nbd_aio_flush \ - nbd_aio_trim \ - nbd_aio_cache \ - nbd_aio_zero \ - nbd_aio_block_status \ - nbd_aio_get_fd \ - nbd_aio_get_direction \ - nbd_aio_notify_read \ - nbd_aio_notify_write \ - nbd_aio_is_created \ - nbd_aio_is_connecting \ - nbd_aio_is_ready \ - nbd_aio_is_processing \ - nbd_aio_is_dead \ - nbd_aio_is_closed \ - nbd_aio_command_completed \ - nbd_aio_peek_command_completed \ - nbd_aio_in_flight \ - nbd_connection_state \ - nbd_get_package_name \ - nbd_get_version \ - nbd_kill_command \ - nbd_supports_tls \ - nbd_supports_uri \ - $(NULL)...

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