On Thu, Aug 03, 2023 at 03:30:36PM +0000, Tage Johansson wrote:
>
> On 8/2/2023 6:39 PM, Richard W.M. Jones wrote:
> >On Wed, Aug 02, 2023 at 12:40:53PM +0000, Tage Johansson wrote:
> >>Add a flag (`modifies_fd`) to the [call] structure in generator/API.ml
> >>which is set to [true] if the handle call may do something with the
> >>file descriptor. That is, it is [true] for all calls which are or may
> >>call [aio_notify_*], including all synchronous commands like
> >>[nbd_connect] or [nbd_opt_go].
> >>
> >>The motivation for this is that the asynchronous handle in the Rust
> >>bindings uses its own loop for polling, modifying the file descriptor
> >>outside of this loop may cause unexpected behaviour. Including that the
> >>handle may hang. All commands which set this flag to [true] will be
> >>excluded from that handle. The asynchronous (`aio_*`) functions will be
> >>used instead.
> >Isn't this just saying that the call is synchronous?
> >
> >Rich.
>
>
> Kind of, it is true for all synchronous commands and the functions
> aio_notify_read() and aio_notify_write(). I could mention those
> explicitly though and rename the flag to something like
> "is_synchronous", if you want?
No it'll be fine, thanks.
Rich.
>
> Best regards,
>
> Tage
>
>
> >>---
> >> generator/API.ml | 32 ++++++++++++++++++++++++++++++++
> >> generator/API.mli | 7 +++++++
> >> 2 files changed, 39 insertions(+)
> >>
> >>diff --git a/generator/API.ml b/generator/API.ml
> >>index 42b9eec..6e1670d 100644
> >>--- a/generator/API.ml
> >>+++ b/generator/API.ml
> >>@@ -33,6 +33,7 @@ type call = {
> >> is_locked : bool;
> >> may_set_error : bool;
> >> async_kind : async_kind option;
> >>+ modifies_fd: bool;
> >> mutable first_version : int * int;
> >> }
> >> and arg =
> >>@@ -274,6 +275,7 @@ let default_call = { args = []; optargs = []; ret =
> >>RErr;
> >> permitted_states = [];
> >> is_locked = true; may_set_error = true;
> >> async_kind = None;
> >>+ modifies_fd = false;
> >> first_version = (0, 0) }
> >> (* Calls.
> >>@@ -1181,6 +1183,7 @@ Return true if option negotiation mode was enabled on
> >>this handle.";
> >> default_call with
> >> args = []; ret = RErr;
> >> permitted_states = [ Negotiating ];
> >>+ modifies_fd = true;
> >> shortdesc = "end negotiation and move on to using an export";
> >> longdesc = "\
> >> Request that the server finish negotiation and move on to serving the
> >>@@ -1208,6 +1211,7 @@ although older servers will instead have killed the
> >>connection.";
> >> default_call with
> >> args = []; ret = RErr;
> >> permitted_states = [ Negotiating ];
> >>+ modifies_fd = true;
> >> shortdesc = "end negotiation and close the connection";
> >> longdesc = "\
> >> Request that the server finish negotiation, gracefully if possible, then
> >>@@ -1221,6 +1225,7 @@ enabled option mode.";
> >> default_call with
> >> args = []; ret = RBool;
> >> permitted_states = [ Negotiating ];
> >>+ modifies_fd = true;
> >> shortdesc = "request the server to initiate TLS";
> >> longdesc = "\
> >> Request that the server initiate a secure TLS connection, by
> >>@@ -1259,6 +1264,7 @@ established, as reported by
> >>L<nbd_get_tls_negotiated(3)>.";
> >> default_call with
> >> args = []; ret = RBool;
> >> permitted_states = [ Negotiating ];
> >>+ modifies_fd = true;
> >> shortdesc = "request the server to enable structured replies";
> >> longdesc = "\
> >> Request that the server use structured replies, by sending
> >>@@ -1285,6 +1291,7 @@ later calls to this function return false.";
> >> default_call with
> >> args = [ Closure list_closure ]; ret = RInt;
> >> permitted_states = [ Negotiating ];
> >>+ modifies_fd = true;
> >> shortdesc = "request the server to list all exports during
> >> negotiation";
> >> longdesc = "\
> >> Request that the server list all exports that it supports. This can
> >>@@ -1326,6 +1333,7 @@ description is set with I<-D>.";
> >> default_call with
> >> args = []; ret = RErr;
> >> permitted_states = [ Negotiating ];
> >>+ modifies_fd = true;
> >> shortdesc = "request the server for information about an export";
> >> longdesc = "\
> >> Request that the server supply information about the export name
> >>@@ -1357,6 +1365,7 @@ corresponding L<nbd_opt_go(3)> would succeed.";
> >> default_call with
> >> args = [ Closure context_closure ]; ret = RInt;
> >> permitted_states = [ Negotiating ];
> >>+ modifies_fd = true;
> >> shortdesc = "list available meta contexts, using implicit query list";
> >> longdesc = "\
> >> Request that the server list available meta contexts associated with
> >>@@ -1412,6 +1421,7 @@ a server may send a lengthy list.";
> >> default_call with
> >> args = [ StringList "queries"; Closure context_closure ]; ret = RInt;
> >> permitted_states = [ Negotiating ];
> >>+ modifies_fd = true;
> >> shortdesc = "list available meta contexts, using explicit query list";
> >> longdesc = "\
> >> Request that the server list available meta contexts associated with
> >>@@ -1462,6 +1472,7 @@ a server may send a lengthy list.";
> >> default_call with
> >> args = [ Closure context_closure ]; ret = RInt;
> >> permitted_states = [ Negotiating ];
> >>+ modifies_fd = true;
> >> shortdesc = "select specific meta contexts, using implicit query
> >> list";
> >> longdesc = "\
> >> Request that the server supply all recognized meta contexts
> >>@@ -1521,6 +1532,7 @@ no contexts are reported, or may fail but have a
> >>non-empty list.";
> >> default_call with
> >> args = [ StringList "queries"; Closure context_closure ]; ret = RInt;
> >> permitted_states = [ Negotiating ];
> >>+ modifies_fd = true;
> >> shortdesc = "select specific meta contexts, using explicit query
> >> list";
> >> longdesc = "\
> >> Request that the server supply all recognized meta contexts
> >>@@ -1750,6 +1762,7 @@ parameter in NBD URIs is allowed.";
> >> default_call with
> >> args = [ String "uri" ]; ret = RErr;
> >> permitted_states = [ Created ];
> >>+ modifies_fd = true;
> >> shortdesc = "connect to NBD URI";
> >> longdesc = "\
> >> Connect (synchronously) to an NBD server and export by specifying
> >>@@ -1928,6 +1941,7 @@ See L<nbd_get_uri(3)>.";
> >> default_call with
> >> args = [ Path "unixsocket" ]; ret = RErr;
> >> permitted_states = [ Created ];
> >>+ modifies_fd = true;
> >> shortdesc = "connect to NBD server over a Unix domain socket";
> >> longdesc = "\
> >> Connect (synchronously) over the named Unix domain socket (C<unixsocket>)
> >>@@ -1941,6 +1955,7 @@ to an NBD server running on the same machine.
> >> default_call with
> >> args = [ UInt32 "cid"; UInt32 "port" ]; ret = RErr;
> >> permitted_states = [ Created ];
> >>+ modifies_fd = true;
> >> shortdesc = "connect to NBD server over AF_VSOCK protocol";
> >> longdesc = "\
> >> Connect (synchronously) over the C<AF_VSOCK> protocol from a
> >>@@ -1961,6 +1976,7 @@ built on a system with vsock support, see
> >>L<nbd_supports_vsock(3)>.
> >> default_call with
> >> args = [ String "hostname"; String "port" ]; ret = RErr;
> >> permitted_states = [ Created ];
> >>+ modifies_fd = true;
> >> shortdesc = "connect to NBD server over a TCP port";
> >> longdesc = "\
> >> Connect (synchronously) to the NBD server listening on
> >>@@ -1975,6 +1991,7 @@ such as C<\"10809\">.
> >> default_call with
> >> args = [ Fd "sock" ]; ret = RErr;
> >> permitted_states = [ Created ];
> >>+ modifies_fd = true;
> >> shortdesc = "connect directly to a connected socket";
> >> longdesc = "\
> >> Pass a connected socket C<sock> through which libnbd will talk
> >>@@ -1996,6 +2013,7 @@ handle is closed. The caller must not use the socket
> >>in any way.
> >> default_call with
> >> args = [ StringList "argv" ]; ret = RErr;
> >> permitted_states = [ Created ];
> >>+ modifies_fd = true;
> >> shortdesc = "connect to NBD server command";
> >> longdesc = "\
> >> Run the command as a subprocess and connect to it over
> >>@@ -2031,6 +2049,7 @@ is killed.
> >> default_call with
> >> args = [ StringList "argv" ]; ret = RErr;
> >> permitted_states = [ Created ];
> >>+ modifies_fd = true;
> >> shortdesc = "connect using systemd socket activation";
> >> longdesc = "\
> >> Run the command as a subprocess and connect to it using
> >>@@ -2404,6 +2423,7 @@ requests sizes.
> >> optargs = [ OFlags ("flags", cmd_flags, Some []) ];
> >> ret = RErr;
> >> permitted_states = [ Connected ];
> >>+ modifies_fd = true;
> >> shortdesc = "read from the NBD server";
> >> longdesc = "\
> >> Issue a read command to the NBD server for the range starting
> >>@@ -2443,6 +2463,7 @@ on failure."
> >> optargs = [ OFlags ("flags", cmd_flags, Some ["DF"]) ];
> >> ret = RErr;
> >> permitted_states = [ Connected ];
> >>+ modifies_fd = true;
> >> shortdesc = "read from the NBD server";
> >> longdesc = "\
> >> Issue a read command to the NBD server for the range starting
> >>@@ -2535,6 +2556,7 @@ on failure."
> >> optargs = [ OFlags ("flags", cmd_flags, Some ["FUA"]) ];
> >> ret = RErr;
> >> permitted_states = [ Connected ];
> >>+ modifies_fd = true;
> >> shortdesc = "write to the NBD server";
> >> longdesc = "\
> >> Issue a write command to the NBD server, writing the data in
> >>@@ -2568,6 +2590,7 @@ L<nbd_can_fua(3)>)."
> >> args = []; optargs = [ OFlags ("flags", shutdown_flags, None) ];
> >> ret = RErr;
> >> permitted_states = [ Connected ];
> >>+ modifies_fd = true;
> >> shortdesc = "disconnect from the NBD server";
> >> longdesc = "\
> >> Issue the disconnect command to the NBD server. This is
> >>@@ -2605,6 +2628,7 @@ A future version of the library may add new flags.";
> >> default_call with
> >> args = []; optargs = [ OFlags ("flags", cmd_flags, Some []) ]; ret =
> >> RErr;
> >> permitted_states = [ Connected ];
> >>+ modifies_fd = true;
> >> shortdesc = "send flush command to the NBD server";
> >> longdesc = "\
> >> Issue the flush command to the NBD server. The function should
> >>@@ -2625,6 +2649,7 @@ protocol extensions)."
> >> optargs = [ OFlags ("flags", cmd_flags, Some ["FUA"]) ];
> >> ret = RErr;
> >> permitted_states = [ Connected ];
> >>+ modifies_fd = true;
> >> shortdesc = "send trim command to the NBD server";
> >> longdesc = "\
> >> Issue a trim command to the NBD server, which if supported
> >>@@ -2656,6 +2681,7 @@ L<nbd_can_fua(3)>)."
> >> optargs = [ OFlags ("flags", cmd_flags, Some []) ];
> >> ret = RErr;
> >> permitted_states = [ Connected ];
> >>+ modifies_fd = true;
> >> shortdesc = "send cache (prefetch) command to the NBD server";
> >> longdesc = "\
> >> Issue the cache (prefetch) command to the NBD server, which
> >>@@ -2685,6 +2711,7 @@ protocol extensions)."
> >> Some ["FUA"; "NO_HOLE"; "FAST_ZERO"]) ];
> >> ret = RErr;
> >> permitted_states = [ Connected ];
> >>+ modifies_fd = true;
> >> shortdesc = "send write zeroes command to the NBD server";
> >> longdesc = "\
> >> Issue a write zeroes command to the NBD server, which if supported
> >>@@ -2723,6 +2750,7 @@ cannot do this, see L<nbd_can_fast_zero(3)>)."
> >> optargs = [ OFlags ("flags", cmd_flags, Some ["REQ_ONE"]) ];
> >> ret = RErr;
> >> permitted_states = [ Connected ];
> >>+ modifies_fd = true;
> >> shortdesc = "send block status command to the NBD server";
> >> longdesc = "\
> >> Issue the block status command to the NBD server. If
> >>@@ -2789,6 +2817,7 @@ validate that the server obeyed the flag."
> >> "poll", {
> >> default_call with
> >> args = [ Int "timeout" ]; ret = RInt;
> >>+ modifies_fd = true;
> >> shortdesc = "poll the handle once";
> >> longdesc = "\
> >> This is a simple implementation of L<poll(2)> which is used
> >>@@ -2810,6 +2839,7 @@ intended as something you would use.";
> >> "poll2", {
> >> default_call with
> >> args = [Fd "fd"; Int "timeout" ]; ret = RInt;
> >>+ modifies_fd = true;
> >> shortdesc = "poll the handle once, with fd";
> >> longdesc = "\
> >> This is the same as L<nbd_poll(3)>, but an additional
> >>@@ -3493,6 +3523,7 @@ and invalidate the need to write more commands.
> >> "aio_notify_read", {
> >> default_call with
> >> args = []; ret = RErr;
> >>+ modifies_fd = true;
> >> shortdesc = "notify that the connection is readable";
> >> longdesc = "\
> >> Send notification to the state machine that the connection
> >>@@ -3504,6 +3535,7 @@ connection is readable.";
> >> "aio_notify_write", {
> >> default_call with
> >> args = []; ret = RErr;
> >>+ modifies_fd = true;
> >> shortdesc = "notify that the connection is writable";
> >> longdesc = "\
> >> Send notification to the state machine that the connection
> >>diff --git a/generator/API.mli b/generator/API.mli
> >>index ff85849..4bf4468 100644
> >>--- a/generator/API.mli
> >>+++ b/generator/API.mli
> >>@@ -41,6 +41,13 @@ type call = {
> >> if the function is asynchronous and in that case how one can check
> >> if
> >> it has completed. *)
> >> async_kind : async_kind option;
> >>+ (** A flag telling if the call may do something with the file descriptor.
> >>+ Some bindings needs exclusive access to the file descriptor and can
> >>not
> >>+ allow the user to call [aio_notify_read] or [aio_notify_write],
> >>neither
> >>+ directly nor indirectly from another call. So all calls that might
> >>trigger
> >>+ any of these functions to be called, including all synchronous
> >>commands
> >>+ like [pread] or [connect], should set this to [true]. *)
> >>+ modifies_fd : bool;
> >> (** The first stable version that the symbol appeared in, for
> >> example (1, 2) if the symbol was added in development cycle
> >> 1.1.x and thus the first stable version was 1.2. This is
> >>--
> >>2.41.0
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
Fedora Windows cross-compiler. Compile Windows programs, test, and
build Windows installers. Over 100 libraries supported.
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