aio: add I/O handlers to the AioContext interface

With this patch, I/O handlers (including event notifier handlers) can be
attached to a single AioContext.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

aio.c

@@ -18,15 +18,6 @@
 #include "qemu-queue.h"
 #include "qemu_socket.h"
 
-/* The list of registered AIO handlers */
-static QLIST_HEAD(, AioHandler) aio_handlers;
-
-/* This is a simple lock used to protect the aio_handlers list.  Specifically,
- * it's used to ensure that no callbacks are removed while we're walking and
- * dispatching callbacks.
- */
-static int walking_handlers;
-
 struct AioHandler
 {
     int fd;
@@ -38,11 +29,11 @@ struct AioHandler
     QLIST_ENTRY(AioHandler) node;
 };
 
-static AioHandler *find_aio_handler(int fd)
+static AioHandler *find_aio_handler(AioContext *ctx, int fd)
 {
     AioHandler *node;
 
-    QLIST_FOREACH(node, &aio_handlers, node) {
+    QLIST_FOREACH(node, &ctx->aio_handlers, node) {
         if (node->fd == fd)
             if (!node->deleted)
                 return node;
@@ -51,21 +42,22 @@ static AioHandler *find_aio_handler(int fd)
     return NULL;
 }
 
-void qemu_aio_set_fd_handler(int fd,
-                             IOHandler *io_read,
-                             IOHandler *io_write,
-                             AioFlushHandler *io_flush,
-                             void *opaque)
+void aio_set_fd_handler(AioContext *ctx,
+                        int fd,
+                        IOHandler *io_read,
+                        IOHandler *io_write,
+                        AioFlushHandler *io_flush,
+                        void *opaque)
 {
     AioHandler *node;
 
-    node = find_aio_handler(fd);
+    node = find_aio_handler(ctx, fd);
 
     /* Are we deleting the fd handler? */
     if (!io_read && !io_write) {
         if (node) {
             /* If the lock is held, just mark the node as deleted */
-            if (walking_handlers)
+            if (ctx->walking_handlers)
                 node->deleted = 1;
             else {
                 /* Otherwise, delete it for real.  We can't just mark it as
@@ -81,7 +73,7 @@ void qemu_aio_set_fd_handler(int fd,
             /* Alloc and insert if it's not already there */
             node = g_malloc0(sizeof(AioHandler));
             node->fd = fd;
-            QLIST_INSERT_HEAD(&aio_handlers, node, node);
+            QLIST_INSERT_HEAD(&ctx->aio_handlers, node, node);
         }
         /* Update handler with latest information */
         node->io_read = io_read;
@@ -89,25 +81,19 @@ void qemu_aio_set_fd_handler(int fd,
         node->io_flush = io_flush;
         node->opaque = opaque;
     }
-
-    qemu_set_fd_handler2(fd, NULL, io_read, io_write, opaque);
-}
-
-void qemu_aio_set_event_notifier(EventNotifier *notifier,
-                                 EventNotifierHandler *io_read,
-                                 AioFlushEventNotifierHandler *io_flush)
-{
-    qemu_aio_set_fd_handler(event_notifier_get_fd(notifier),
-                            (IOHandler *)io_read, NULL,
-                            (AioFlushHandler *)io_flush, notifier);
 }
 
-void qemu_aio_flush(void)
+void aio_set_event_notifier(AioContext *ctx,
+                            EventNotifier *notifier,
+                            EventNotifierHandler *io_read,
+                            AioFlushEventNotifierHandler *io_flush)
 {
-    while (qemu_aio_wait());
+    aio_set_fd_handler(ctx, event_notifier_get_fd(notifier),
+                       (IOHandler *)io_read, NULL,
+                       (AioFlushHandler *)io_flush, notifier);
 }
 
-bool qemu_aio_wait(void)
+bool aio_wait(AioContext *ctx)
 {
     AioHandler *node;
     fd_set rdfds, wrfds;
@@ -120,18 +106,18 @@ bool qemu_aio_wait(void)
      * Do not call select in this case, because it is possible that the caller
      * does not need a complete flush (as is the case for qemu_aio_wait loops).
      */
-    if (qemu_bh_poll()) {
+    if (aio_bh_poll(ctx)) {
         return true;
     }
 
-    walking_handlers++;
+    ctx->walking_handlers++;
 
     FD_ZERO(&rdfds);
     FD_ZERO(&wrfds);
 
     /* fill fd sets */
     busy = false;
-    QLIST_FOREACH(node, &aio_handlers, node) {
+    QLIST_FOREACH(node, &ctx->aio_handlers, node) {
         /* If there aren't pending AIO operations, don't invoke callbacks.
          * Otherwise, if there are no AIO requests, qemu_aio_wait() would
          * wait indefinitely.
@@ -152,7 +138,7 @@ bool qemu_aio_wait(void)
         }
     }
 
-    walking_handlers--;
+    ctx->walking_handlers--;
 
     /* No AIO operations?  Get us out of here */
     if (!busy) {
@@ -166,11 +152,11 @@ bool qemu_aio_wait(void)
     if (ret > 0) {
         /* we have to walk very carefully in case
          * qemu_aio_set_fd_handler is called while we're walking */
-        node = QLIST_FIRST(&aio_handlers);
+        node = QLIST_FIRST(&ctx->aio_handlers);
         while (node) {
             AioHandler *tmp;
 
-            walking_handlers++;
+            ctx->walking_handlers++;
 
             if (!node->deleted &&
                 FD_ISSET(node->fd, &rdfds) &&
@@ -186,9 +172,9 @@ bool qemu_aio_wait(void)
             tmp = node;
             node = QLIST_NEXT(node, node);
 
-            walking_handlers--;
+            ctx->walking_handlers--;
 
-            if (!walking_handlers && tmp->deleted) {
+            if (!ctx->walking_handlers && tmp->deleted) {
                 QLIST_REMOVE(tmp, node);
                 g_free(tmp);
             }

async.c

@@ -136,7 +136,13 @@ void aio_bh_update_timeout(AioContext *ctx, uint32_t *timeout)
     }
 }
 
+
 AioContext *aio_context_new(void)
 {
     return g_new0(AioContext, 1);
 }
+
+void aio_flush(AioContext *ctx)
+{
+    while (aio_wait(ctx));
+}

main-loop.c

@@ -526,3 +526,36 @@ int qemu_bh_poll(void)
 {
     return aio_bh_poll(qemu_aio_context);
 }
+
+void qemu_aio_flush(void)
+{
+    aio_flush(qemu_aio_context);
+}
+
+bool qemu_aio_wait(void)
+{
+    return aio_wait(qemu_aio_context);
+}
+
+void qemu_aio_set_fd_handler(int fd,
+                             IOHandler *io_read,
+                             IOHandler *io_write,
+                             AioFlushHandler *io_flush,
+                             void *opaque)
+{
+    aio_set_fd_handler(qemu_aio_context, fd, io_read, io_write, io_flush,
+                       opaque);
+
+    qemu_set_fd_handler2(fd, NULL, io_read, io_write, opaque);
+}
+
+#ifdef CONFIG_POSIX
+void qemu_aio_set_event_notifier(EventNotifier *notifier,
+                                 EventNotifierHandler *io_read,
+                                 AioFlushEventNotifierHandler *io_flush)
+{
+    qemu_aio_set_fd_handler(event_notifier_get_fd(notifier),
+                            (IOHandler *)io_read, NULL,
+                            (AioFlushHandler *)io_flush, notifier);
+}
+#endif

qemu-aio.h

@@ -15,6 +15,7 @@
 #define QEMU_AIO_H
 
 #include "qemu-common.h"
+#include "qemu-queue.h"
 #include "event_notifier.h"
 
 typedef struct BlockDriverAIOCB BlockDriverAIOCB;
@@ -43,6 +44,15 @@ typedef void QEMUBHFunc(void *opaque);
 typedef void IOHandler(void *opaque);
 
 typedef struct AioContext {
+    /* The list of registered AIO handlers */
+    QLIST_HEAD(, AioHandler) aio_handlers;
+
+    /* This is a simple lock used to protect the aio_handlers list.
+     * Specifically, it's used to ensure that no callbacks are removed while
+     * we're walking and dispatching callbacks.
+     */
+    int walking_handlers;
+
     /* Anchor of the list of Bottom Halves belonging to the context */
     struct QEMUBH *first_bh;
 
@@ -121,7 +131,7 @@ void qemu_bh_delete(QEMUBH *bh);
 
 /* Flush any pending AIO operation. This function will block until all
  * outstanding AIO operations have been completed or cancelled. */
-void qemu_aio_flush(void);
+void aio_flush(AioContext *ctx);
 
 /* Wait for a single AIO completion to occur.  This function will wait
  * until a single AIO event has completed and it will ensure something
@@ -129,7 +139,7 @@ void qemu_aio_flush(void);
  * result of executing I/O completion or bh callbacks.
  *
  * Return whether there is still any pending AIO operation.  */
-bool qemu_aio_wait(void);
+bool aio_wait(AioContext *ctx);
 
 #ifdef CONFIG_POSIX
 /* Returns 1 if there are still outstanding AIO requests; 0 otherwise */
@@ -142,11 +152,12 @@ typedef int (AioFlushHandler)(void *opaque);
  * Code that invokes AIO completion functions should rely on this function
  * instead of qemu_set_fd_handler[2].
  */
-void qemu_aio_set_fd_handler(int fd,
-                             IOHandler *io_read,
-                             IOHandler *io_write,
-                             AioFlushHandler *io_flush,
-                             void *opaque);
+void aio_set_fd_handler(AioContext *ctx,
+                        int fd,
+                        IOHandler *io_read,
+                        IOHandler *io_write,
+                        AioFlushHandler *io_flush,
+                        void *opaque);
 #endif
 
 /* Register an event notifier and associated callbacks.  Behaves very similarly
@@ -156,8 +167,25 @@ void qemu_aio_set_fd_handler(int fd,
  * Code that invokes AIO completion functions should rely on this function
  * instead of event_notifier_set_handler.
  */
+void aio_set_event_notifier(AioContext *ctx,
+                            EventNotifier *notifier,
+                            EventNotifierHandler *io_read,
+                            AioFlushEventNotifierHandler *io_flush);
+
+/* Functions to operate on the main QEMU AioContext.  */
+
+void qemu_aio_flush(void);
+bool qemu_aio_wait(void);
 void qemu_aio_set_event_notifier(EventNotifier *notifier,
                                  EventNotifierHandler *io_read,
                                  AioFlushEventNotifierHandler *io_flush);
 
+#ifdef CONFIG_POSIX
+void qemu_aio_set_fd_handler(int fd,
+                             IOHandler *io_read,
+                             IOHandler *io_write,
+                             AioFlushHandler *io_flush,
+                             void *opaque);
+#endif
+
 #endif