search for: nbd_aio_pread

On 8/13/19 5:36 PM, Richard W.M. Jones wrote: > The definition of functions that take a callback is changed so that > the callback and user_data are combined into a single structure, eg: > > int64_t nbd_aio_pread (struct nbd_handle *h, > void *buf, size_t count, uint64_t offset, > - int (*completion_callback) (/*..*/), void *user_data, > + nbd_completion_callback completion_callback, > uint32_t flags); > > Several nbd_*_callback structures are d...

On Tue, Aug 13, 2019 at 10:06:06PM -0500, Eric Blake wrote: > On 8/13/19 5:36 PM, Richard W.M. Jones wrote: > > The definition of functions that take a callback is changed so that > > the callback and user_data are combined into a single structure, eg: > > > > int64_t nbd_aio_pread (struct nbd_handle *h, > > void *buf, size_t count, uint64_t offset, > > - int (*completion_callback) (/*..*/), void *user_data, > > + nbd_completion_callback completion_callback, > > uint32_t flags); > > > > Several n...

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) -----...

This applies on top of the OClosure v2 series posted a few minutes ago. Rich.

The definition of functions that take a callback is changed so that the callback and user_data are combined into a single structure, eg: int64_t nbd_aio_pread (struct nbd_handle *h, void *buf, size_t count, uint64_t offset, - int (*completion_callback) (/*..*/), void *user_data, + nbd_completion_callback completion_callback, uint32_t flags); Several nbd_*_callback structures are defined. The one corresponding...

...diff --git a/docs/libnbd.pod b/docs/libnbd.pod index 51b1a03..aeecaee 100644 --- a/docs/libnbd.pod +++ b/docs/libnbd.pod @@ -276,9 +276,8 @@ command has completed: } For almost all high level synchronous calls (eg. C<nbd_pread>) there -are two low level asynchronous equivalents (eg. C<nbd_aio_pread> for -starting a command, and C<nbd_aio_pread_callback> for also registering -a callback to be invoked right before the command is complete). +is a low level asynchronous equivalents (eg. C<nbd_aio_pread> for +starting a command). =head2 glib2 integration @@ -600,8 +599,8 @@ wil...

On Mon, Aug 12, 2019 at 11:00:01PM +0100, Richard W.M. Jones wrote: > On Mon, Aug 12, 2019 at 01:53:56PM -0500, Eric Blake wrote: > > We then have the design question of whether to make an OClosure type, > > where C has two functions nbd_aio_pread and nbd_aio_pread_callback for > > convenience, but where other languages have only a single nbd.aio_pread > > where the callback parameter is optional (the Closure type for > > pread_structured chunk and for block_status extent will still be > > mandatory; it is only the co...

...nbd_aio_* > > (2) Any existing call to nbd_aio_* must have two extra NULL parameters > added before the final flags parameter. > > In non-C languages, only change (1) is required. It is still possible to compile for 0.9.6 and this patch simultaneously, by checking LIBNBD_HAVE_NBD_AIO_PREAD_CALLBACK as a witness of which API style to use (although it's also just as easy to bump minimum version requirements to 0.9.7, once we have a release including this and any other API changes being discussed...). > +++ b/docs/libnbd.pod > @@ -276,9 +276,8 @@ command has completed: >...

On 8/14/19 4:21 AM, Richard W.M. Jones wrote: >>> The nbd_aio_pread function can now be called using: >>> >>> nbd_aio_pread (nbd, buf, sizeof buf, offset, >>> (nbd_completion_callback) { .callback = my_fn, >>> .user_data = my_data }, >> >> Is it worth arr...

...lue *callback; }; struct closure_wrap *wrap = malloc (sizeof *wrap); wrap->buf = malloc (sizeof (*wrap->buf)); caml_register_generational_global_root (wrap->buf); struct nbd_buffer *buf_buf = NBD_buffer_val (bufv); const void *buf = buf_buf->data; size_t count = buf_buf->len; if (in nbd_aio_pread) { wrap->callback = NULL; res = nbd_aio_pread_callback(h, buf, count, offset, NULL, free_cb, wrap, flags); } else /* in nbd_aio_pread_callback */ { wrap->callback = ...; res = nbd_aio_pread_callback(h, buf, count, offset,...

On Tue, Jul 30, 2019 at 11:21:25AM -0500, Eric Blake wrote: > On 7/30/19 10:36 AM, Richard W.M. Jones wrote: > > +When the command completes, C<callback> > > will be invoked as described in L<libnbd(3)/Completion callbacks>. > > + > > Do we need wording anywhere (probably in the .pod, so we only state it > once) that mentions that the callback routine is

Patches 1 & 2 are rather complex, but the end result is that we pass closures + user_data + free function in single struct parameters as I described previously in this email: https://www.redhat.com/archives/libguestfs/2019-August/msg00210.html Patch 3 adds a convenient FREE_CALLBACK macro which seems a worthwhile simplification if you buy into 1 & 2. Patch 4 adds another macro which is

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

...amp;& 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, sizeof buf, offset, 0); + if (handle == -1) { + fprintf (stderr, "%s\n", nbd_get_error ()); + goto error; + } + handles[in_flight] = handle; + i--; + in_flight++; + if (in_flight > status->most_in_flight) + status->mos...

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...

On Mon, Aug 12, 2019 at 01:53:56PM -0500, Eric Blake wrote: > We then have the design question of whether to make an OClosure type, > where C has two functions nbd_aio_pread and nbd_aio_pread_callback for > convenience, but where other languages have only a single nbd.aio_pread > where the callback parameter is optional (the Closure type for > pread_structured chunk and for block_status extent will still be > mandatory; it is only the completion callback th...

RFC because this is an API break, but we haven't declared stable API yet. If we like it, I'm working on using libnbd to implement the nbdkit-nbd plugin; knowing whether it is API version 0.1 or 0.2 will be useful. I also dabbled with allowing optional parameters in python, although my OCaml is weak enough that there may be cleaner ways to approach that. Eric Blake (4): api: Add flags

...r BOTH (== READ|WRITE). You then set up some events mechanism (eg. poll, epoll, etc.), poll until the file descriptor is ready, and call one of nbd_aio_notify_read or nbd_aio_notify_write. The direction can change any time the handle state changes, which includes whenever you issue a command (eg. nbd_aio_pread), or whenever you call nbd_aio_notify_*. You therefore have to call nbd_aio_get_direction frequently. A typical loop using poll might look like: fd = nbd_aio_get_fd (nbd); for (;;) { /* <-- If you need to issue more commands, do that here. */ dir = nbd_aio_get_direction (nbd);...

...ather, until we can tell if the server negotiated extended mode, we are ASSUMING that the server did NOT negotiate it, and therefore we are in violation of the spec if we send the flag over the wire anyways. We can flag all other API where it is inappropriate to ever use... > > > + if (nbd_aio_pread (nbd, buf, 512, 0, NBD_NULL_COMPLETION, > > + LIBNBD_CMD_FLAG_PAYLOAD_LEN) != -1) { > > + fprintf (stderr, "%s: test failed: " > > + "nbd_aio_pread did not fail with unexpected flag\n", > > + argv[0]); > &...

I'm not sure if this is worth pursuing. On paper, it makes sense (if we know we have multiple commands batched to send over the wire, AND those commands are short in length, we might as well use MSG_MORE), but the measurement numbers with it applied might just be in the noise. Eric Blake (2): examples: Enhance access patterns of threaded-reads-and-writes states: Another use for MSG_MORE