Merge tag 'pull-nbd-2023-09-07-v2' of https://repo.or.cz/qemu/ericb into staging

NBD patches for 2023-09-07

- Andrey Drobyshev - fix regression in iotest 197 under -nbd
- Stefan Hajnoczi - allow coroutine read and write context to split
across threads
- Philippe Mathieu-Daudé - remove a VLA allocation
- Denis V. Lunev - fix regression in iotest 233 with qemu-nbd -v --fork

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# gpg: Signature made Fri 08 Sep 2023 08:25:41 EDT
# gpg:                using RSA key 71C2CC22B1C4602927D2F3AAA7A16B4A2527436A
# gpg: Good signature from "Eric Blake <eblake@redhat.com>" [full]
# gpg:                 aka "Eric Blake (Free Software Programmer) <ebb9@byu.net>" [full]
# gpg:                 aka "[jpeg image of size 6874]" [full]
# Primary key fingerprint: 71C2 CC22 B1C4 6029 27D2  F3AA A7A1 6B4A 2527 436A

* tag 'pull-nbd-2023-09-07-v2' of https://repo.or.cz/qemu/ericb:
  qemu-nbd: document -v behavior in respect to --fork in man
  qemu-nbd: Restore "qemu-nbd -v --fork" output
  qemu-nbd: invent nbd_client_release_pipe() helper
  qemu-nbd: put saddr into into struct NbdClientOpts
  qemu-nbd: move srcpath into struct NbdClientOpts
  qemu-nbd: define struct NbdClientOpts when HAVE_NBD_DEVICE is not defined
  qemu-nbd: improve error message for dup2 error
  util/iov: Avoid dynamic stack allocation
  io: follow coroutine AioContext in qio_channel_yield()
  io: check there are no qio_channel_yield() coroutines during ->finalize()
  nbd: drop unused nbd_start_negotiate() aio_context argument
  nbd: drop unused nbd_receive_negotiate() aio_context argument
  qemu-iotests/197: use more generic commands for formats other than qcow2

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

4 files changed, 55 insertions, 41 deletions

diff --git a/include/block/nbd.h b/include/block/nbd.h
index 4428bcf..f672b76 100644
--- a/include/block/nbd.h
+++ b/include/block/nbd.h
@@ -324,8 +324,7 @@ typedef struct NBDExportInfo {
     char **contexts;
 } NBDExportInfo;
 
-int nbd_receive_negotiate(AioContext *aio_context, QIOChannel *ioc,
-                          QCryptoTLSCreds *tlscreds,
+int nbd_receive_negotiate(QIOChannel *ioc, QCryptoTLSCreds *tlscreds,
                           const char *hostname, QIOChannel **outioc,
                           NBDExportInfo *info, Error **errp);
 void nbd_free_export_list(NBDExportInfo *info, int count);
diff --git a/include/io/channel-util.h b/include/io/channel-util.h
index a5d720d..fa18a37 100644
--- a/include/io/channel-util.h
+++ b/include/io/channel-util.h
@@ -49,4 +49,27 @@
 QIOChannel *qio_channel_new_fd(int fd,
                                Error **errp);
 
+/**
+ * qio_channel_util_set_aio_fd_handler:
+ * @read_fd: the file descriptor for the read handler
+ * @read_ctx: the AioContext for the read handler
+ * @io_read: the read handler
+ * @write_fd: the file descriptor for the write handler
+ * @write_ctx: the AioContext for the write handler
+ * @io_write: the write handler
+ * @opaque: the opaque argument to the read and write handler
+ *
+ * Set the read and write handlers when @read_ctx and @write_ctx are non-NULL,
+ * respectively. To leave a handler in its current state, pass a NULL
+ * AioContext. To clear a handler, pass a non-NULL AioContext and a NULL
+ * handler.
+ */
+void qio_channel_util_set_aio_fd_handler(int read_fd,
+                                         AioContext *read_ctx,
+                                         IOHandler *io_read,
+                                         int write_fd,
+                                         AioContext *write_ctx,
+                                         IOHandler *io_write,
+                                         void *opaque);
+
 #endif /* QIO_CHANNEL_UTIL_H */
diff --git a/include/io/channel.h b/include/io/channel.h
index 229bf36..5f9dbaa 100644
--- a/include/io/channel.h
+++ b/include/io/channel.h
@@ -81,9 +81,11 @@ struct QIOChannel {
     Object parent;
     unsigned int features; /* bitmask of QIOChannelFeatures */
     char *name;
-    AioContext *ctx;
+    AioContext *read_ctx;
     Coroutine *read_coroutine;
+    AioContext *write_ctx;
     Coroutine *write_coroutine;
+    bool follow_coroutine_ctx;
 #ifdef _WIN32
     HANDLE event; /* For use with GSource on Win32 */
 #endif
@@ -140,8 +142,9 @@ struct QIOChannelClass {
                      int whence,
                      Error **errp);
     void (*io_set_aio_fd_handler)(QIOChannel *ioc,
-                                  AioContext *ctx,
+                                  AioContext *read_ctx,
                                   IOHandler *io_read,
+                                  AioContext *write_ctx,
                                   IOHandler *io_write,
                                   void *opaque);
     int (*io_flush)(QIOChannel *ioc,
@@ -499,6 +502,21 @@ int qio_channel_set_blocking(QIOChannel *ioc,
                              Error **errp);
 
 /**
+ * qio_channel_set_follow_coroutine_ctx:
+ * @ioc: the channel object
+ * @enabled: whether or not to follow the coroutine's AioContext
+ *
+ * If @enabled is true, calls to qio_channel_yield() use the current
+ * coroutine's AioContext. Usually this is desirable.
+ *
+ * If @enabled is false, calls to qio_channel_yield() use the global iohandler
+ * AioContext. This is may be used by coroutines that run in the main loop and
+ * do not wish to respond to I/O during nested event loops. This is the
+ * default for compatibility with code that is not aware of AioContexts.
+ */
+void qio_channel_set_follow_coroutine_ctx(QIOChannel *ioc, bool enabled);
+
+/**
  * qio_channel_close:
  * @ioc: the channel object
  * @errp: pointer to a NULL-initialized error object
@@ -704,41 +722,6 @@ GSource *qio_channel_add_watch_source(QIOChannel *ioc,
                                       GMainContext *context);
 
 /**
- * qio_channel_attach_aio_context:
- * @ioc: the channel object
- * @ctx: the #AioContext to set the handlers on
- *
- * Request that qio_channel_yield() sets I/O handlers on
- * the given #AioContext.  If @ctx is %NULL, qio_channel_yield()
- * uses QEMU's main thread event loop.
- *
- * You can move a #QIOChannel from one #AioContext to another even if
- * I/O handlers are set for a coroutine.  However, #QIOChannel provides
- * no synchronization between the calls to qio_channel_yield() and
- * qio_channel_attach_aio_context().
- *
- * Therefore you should first call qio_channel_detach_aio_context()
- * to ensure that the coroutine is not entered concurrently.  Then,
- * while the coroutine has yielded, call qio_channel_attach_aio_context(),
- * and then aio_co_schedule() to place the coroutine on the new
- * #AioContext.  The calls to qio_channel_detach_aio_context()
- * and qio_channel_attach_aio_context() should be protected with
- * aio_context_acquire() and aio_context_release().
- */
-void qio_channel_attach_aio_context(QIOChannel *ioc,
-                                    AioContext *ctx);
-
-/**
- * qio_channel_detach_aio_context:
- * @ioc: the channel object
- *
- * Disable any I/O handlers set by qio_channel_yield().  With the
- * help of aio_co_schedule(), this allows moving a coroutine that was
- * paused by qio_channel_yield() to another context.
- */
-void qio_channel_detach_aio_context(QIOChannel *ioc);
-
-/**
  * qio_channel_yield:
  * @ioc: the channel object
  * @condition: the I/O condition to wait for
@@ -785,8 +768,9 @@ void qio_channel_wait(QIOChannel *ioc,
 /**
  * qio_channel_set_aio_fd_handler:
  * @ioc: the channel object
- * @ctx: the AioContext to set the handlers on
+ * @read_ctx: the AioContext to set the read handler on or NULL
  * @io_read: the read handler
+ * @write_ctx: the AioContext to set the write handler on or NULL
  * @io_write: the write handler
  * @opaque: the opaque value passed to the handler
  *
@@ -794,10 +778,17 @@ void qio_channel_wait(QIOChannel *ioc,
  * be used by channel implementations to forward the handlers
  * to another channel (e.g. from #QIOChannelTLS to the
  * underlying socket).
+ *
+ * When @read_ctx is NULL, don't touch the read handler. When @write_ctx is
+ * NULL, don't touch the write handler. Note that setting the read handler
+ * clears the write handler, and vice versa, if they share the same AioContext.
+ * Therefore the caller must pass both handlers together when sharing the same
+ * AioContext.
  */
 void qio_channel_set_aio_fd_handler(QIOChannel *ioc,
-                                    AioContext *ctx,
+                                    AioContext *read_ctx,
                                     IOHandler *io_read,
+                                    AioContext *write_ctx,
                                     IOHandler *io_write,
                                     void *opaque);
 
diff --git a/include/qemu/vhost-user-server.h b/include/qemu/vhost-user-server.h
index b1c1cda..64ad701 100644
--- a/include/qemu/vhost-user-server.h
+++ b/include/qemu/vhost-user-server.h
@@ -43,6 +43,7 @@ typedef struct {
     unsigned int in_flight; /* atomic */
 
     /* Protected by ctx lock */
+    bool in_qio_channel_yield;
     bool wait_idle;
     VuDev vu_dev;
     QIOChannel *ioc; /* The I/O channel with the client */