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diff --git a/src/include/block/aio.h b/src/include/block/aio.h
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+/*
+ * QEMU aio implementation
+ *
+ * Copyright IBM, Corp. 2008
+ *
+ * Authors:
+ *  Anthony Liguori   <aliguori@us.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ */
+
+#ifndef QEMU_AIO_H
+#define QEMU_AIO_H
+
+#include "qemu/typedefs.h"
+#include "qemu-common.h"
+#include "qemu/queue.h"
+#include "qemu/event_notifier.h"
+#include "qemu/thread.h"
+#include "qemu/rfifolock.h"
+#include "qemu/timer.h"
+
+typedef struct BlockAIOCB BlockAIOCB;
+typedef void BlockCompletionFunc(void *opaque, int ret);
+
+typedef struct AIOCBInfo {
+    void (*cancel_async)(BlockAIOCB *acb);
+    AioContext *(*get_aio_context)(BlockAIOCB *acb);
+    size_t aiocb_size;
+} AIOCBInfo;
+
+struct BlockAIOCB {
+    const AIOCBInfo *aiocb_info;
+    BlockDriverState *bs;
+    BlockCompletionFunc *cb;
+    void *opaque;
+    int refcnt;
+};
+
+void *qemu_aio_get(const AIOCBInfo *aiocb_info, BlockDriverState *bs,
+                   BlockCompletionFunc *cb, void *opaque);
+void qemu_aio_unref(void *p);
+void qemu_aio_ref(void *p);
+
+typedef struct AioHandler AioHandler;
+typedef void QEMUBHFunc(void *opaque);
+typedef void IOHandler(void *opaque);
+
+struct AioContext {
+    GSource source;
+
+    /* Protects all fields from multi-threaded access */
+    RFifoLock lock;
+
+    /* 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;
+
+    /* Used to avoid unnecessary event_notifier_set calls in aio_notify;
+     * accessed with atomic primitives.  If this field is 0, everything
+     * (file descriptors, bottom halves, timers) will be re-evaluated
+     * before the next blocking poll(), thus the event_notifier_set call
+     * can be skipped.  If it is non-zero, you may need to wake up a
+     * concurrent aio_poll or the glib main event loop, making
+     * event_notifier_set necessary.
+     *
+     * Bit 0 is reserved for GSource usage of the AioContext, and is 1
+     * between a call to aio_ctx_check and the next call to aio_ctx_dispatch.
+     * Bits 1-31 simply count the number of active calls to aio_poll
+     * that are in the prepare or poll phase.
+     *
+     * The GSource and aio_poll must use a different mechanism because
+     * there is no certainty that a call to GSource's prepare callback
+     * (via g_main_context_prepare) is indeed followed by check and
+     * dispatch.  It's not clear whether this would be a bug, but let's
+     * play safe and allow it---it will just cause extra calls to
+     * event_notifier_set until the next call to dispatch.
+     *
+     * Instead, the aio_poll calls include both the prepare and the
+     * dispatch phase, hence a simple counter is enough for them.
+     */
+    uint32_t notify_me;
+
+    /* lock to protect between bh's adders and deleter */
+    QemuMutex bh_lock;
+
+    /* Anchor of the list of Bottom Halves belonging to the context */
+    struct QEMUBH *first_bh;
+
+    /* A simple lock used to protect the first_bh list, and ensure that
+     * no callbacks are removed while we're walking and dispatching callbacks.
+     */
+    int walking_bh;
+
+    /* Used by aio_notify.
+     *
+     * "notified" is used to avoid expensive event_notifier_test_and_clear
+     * calls.  When it is clear, the EventNotifier is clear, or one thread
+     * is going to clear "notified" before processing more events.  False
+     * positives are possible, i.e. "notified" could be set even though the
+     * EventNotifier is clear.
+     *
+     * Note that event_notifier_set *cannot* be optimized the same way.  For
+     * more information on the problem that would result, see "#ifdef BUG2"
+     * in the docs/aio_notify_accept.promela formal model.
+     */
+    bool notified;
+    EventNotifier notifier;
+
+    /* Scheduling this BH forces the event loop it iterate */
+    QEMUBH *notify_dummy_bh;
+
+    /* Thread pool for performing work and receiving completion callbacks */
+    struct ThreadPool *thread_pool;
+
+    /* TimerLists for calling timers - one per clock type */
+    QEMUTimerListGroup tlg;
+
+    int external_disable_cnt;
+
+    /* epoll(7) state used when built with CONFIG_EPOLL */
+    int epollfd;
+    bool epoll_enabled;
+    bool epoll_available;
+};
+
+/**
+ * aio_context_new: Allocate a new AioContext.
+ *
+ * AioContext provide a mini event-loop that can be waited on synchronously.
+ * They also provide bottom halves, a service to execute a piece of code
+ * as soon as possible.
+ */
+AioContext *aio_context_new(Error **errp);
+
+/**
+ * aio_context_ref:
+ * @ctx: The AioContext to operate on.
+ *
+ * Add a reference to an AioContext.
+ */
+void aio_context_ref(AioContext *ctx);
+
+/**
+ * aio_context_unref:
+ * @ctx: The AioContext to operate on.
+ *
+ * Drop a reference to an AioContext.
+ */
+void aio_context_unref(AioContext *ctx);
+
+/* Take ownership of the AioContext.  If the AioContext will be shared between
+ * threads, and a thread does not want to be interrupted, it will have to
+ * take ownership around calls to aio_poll().  Otherwise, aio_poll()
+ * automatically takes care of calling aio_context_acquire and
+ * aio_context_release.
+ *
+ * Access to timers and BHs from a thread that has not acquired AioContext
+ * is possible.  Access to callbacks for now must be done while the AioContext
+ * is owned by the thread (FIXME).
+ */
+void aio_context_acquire(AioContext *ctx);
+
+/* Relinquish ownership of the AioContext. */
+void aio_context_release(AioContext *ctx);
+
+/**
+ * aio_bh_new: Allocate a new bottom half structure.
+ *
+ * Bottom halves are lightweight callbacks whose invocation is guaranteed
+ * to be wait-free, thread-safe and signal-safe.  The #QEMUBH structure
+ * is opaque and must be allocated prior to its use.
+ */
+QEMUBH *aio_bh_new(AioContext *ctx, QEMUBHFunc *cb, void *opaque);
+
+/**
+ * aio_notify: Force processing of pending events.
+ *
+ * Similar to signaling a condition variable, aio_notify forces
+ * aio_wait to exit, so that the next call will re-examine pending events.
+ * The caller of aio_notify will usually call aio_wait again very soon,
+ * or go through another iteration of the GLib main loop.  Hence, aio_notify
+ * also has the side effect of recalculating the sets of file descriptors
+ * that the main loop waits for.
+ *
+ * Calling aio_notify is rarely necessary, because for example scheduling
+ * a bottom half calls it already.
+ */
+void aio_notify(AioContext *ctx);
+
+/**
+ * aio_notify_accept: Acknowledge receiving an aio_notify.
+ *
+ * aio_notify() uses an EventNotifier in order to wake up a sleeping
+ * aio_poll() or g_main_context_iteration().  Calls to aio_notify() are
+ * usually rare, but the AioContext has to clear the EventNotifier on
+ * every aio_poll() or g_main_context_iteration() in order to avoid
+ * busy waiting.  This event_notifier_test_and_clear() cannot be done
+ * using the usual aio_context_set_event_notifier(), because it must
+ * be done before processing all events (file descriptors, bottom halves,
+ * timers).
+ *
+ * aio_notify_accept() is an optimized event_notifier_test_and_clear()
+ * that is specific to an AioContext's notifier; it is used internally
+ * to clear the EventNotifier only if aio_notify() had been called.
+ */
+void aio_notify_accept(AioContext *ctx);
+
+/**
+ * aio_bh_call: Executes callback function of the specified BH.
+ */
+void aio_bh_call(QEMUBH *bh);
+
+/**
+ * aio_bh_poll: Poll bottom halves for an AioContext.
+ *
+ * These are internal functions used by the QEMU main loop.
+ * And notice that multiple occurrences of aio_bh_poll cannot
+ * be called concurrently
+ */
+int aio_bh_poll(AioContext *ctx);
+
+/**
+ * qemu_bh_schedule: Schedule a bottom half.
+ *
+ * Scheduling a bottom half interrupts the main loop and causes the
+ * execution of the callback that was passed to qemu_bh_new.
+ *
+ * Bottom halves that are scheduled from a bottom half handler are instantly
+ * invoked.  This can create an infinite loop if a bottom half handler
+ * schedules itself.
+ *
+ * @bh: The bottom half to be scheduled.
+ */
+void qemu_bh_schedule(QEMUBH *bh);
+
+/**
+ * qemu_bh_cancel: Cancel execution of a bottom half.
+ *
+ * Canceling execution of a bottom half undoes the effect of calls to
+ * qemu_bh_schedule without freeing its resources yet.  While cancellation
+ * itself is also wait-free and thread-safe, it can of course race with the
+ * loop that executes bottom halves unless you are holding the iothread
+ * mutex.  This makes it mostly useless if you are not holding the mutex.
+ *
+ * @bh: The bottom half to be canceled.
+ */
+void qemu_bh_cancel(QEMUBH *bh);
+
+/**
+ *qemu_bh_delete: Cancel execution of a bottom half and free its resources.
+ *
+ * Deleting a bottom half frees the memory that was allocated for it by
+ * qemu_bh_new.  It also implies canceling the bottom half if it was
+ * scheduled.
+ * This func is async. The bottom half will do the delete action at the finial
+ * end.
+ *
+ * @bh: The bottom half to be deleted.
+ */
+void qemu_bh_delete(QEMUBH *bh);
+
+/* Return whether there are any pending callbacks from the GSource
+ * attached to the AioContext, before g_poll is invoked.
+ *
+ * This is used internally in the implementation of the GSource.
+ */
+bool aio_prepare(AioContext *ctx);
+
+/* Return whether there are any pending callbacks from the GSource
+ * attached to the AioContext, after g_poll is invoked.
+ *
+ * This is used internally in the implementation of the GSource.
+ */
+bool aio_pending(AioContext *ctx);
+
+/* Dispatch any pending callbacks from the GSource attached to the AioContext.
+ *
+ * This is used internally in the implementation of the GSource.
+ */
+bool aio_dispatch(AioContext *ctx);
+
+/* Progress in completing AIO work to occur.  This can issue new pending
+ * aio as a result of executing I/O completion or bh callbacks.
+ *
+ * Return whether any progress was made by executing AIO or bottom half
+ * handlers.  If @blocking == true, this should always be true except
+ * if someone called aio_notify.
+ *
+ * If there are no pending bottom halves, but there are pending AIO
+ * operations, it may not be possible to make any progress without
+ * blocking.  If @blocking is true, this function will wait until one
+ * or more AIO events have completed, to ensure something has moved
+ * before returning.
+ */
+bool aio_poll(AioContext *ctx, bool blocking);
+
+/* Register a file descriptor and associated callbacks.  Behaves very similarly
+ * to qemu_set_fd_handler.  Unlike qemu_set_fd_handler, these callbacks will
+ * be invoked when using aio_poll().
+ *
+ * Code that invokes AIO completion functions should rely on this function
+ * instead of qemu_set_fd_handler[2].
+ */
+void aio_set_fd_handler(AioContext *ctx,
+                        int fd,
+                        bool is_external,
+                        IOHandler *io_read,
+                        IOHandler *io_write,
+                        void *opaque);
+
+/* Register an event notifier and associated callbacks.  Behaves very similarly
+ * to event_notifier_set_handler.  Unlike event_notifier_set_handler, these callbacks
+ * will be invoked when using aio_poll().
+ *
+ * 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,
+                            bool is_external,
+                            EventNotifierHandler *io_read);
+
+/* Return a GSource that lets the main loop poll the file descriptors attached
+ * to this AioContext.
+ */
+GSource *aio_get_g_source(AioContext *ctx);
+
+/* Return the ThreadPool bound to this AioContext */
+struct ThreadPool *aio_get_thread_pool(AioContext *ctx);
+
+/**
+ * aio_timer_new:
+ * @ctx: the aio context
+ * @type: the clock type
+ * @scale: the scale
+ * @cb: the callback to call on timer expiry
+ * @opaque: the opaque pointer to pass to the callback
+ *
+ * Allocate a new timer attached to the context @ctx.
+ * The function is responsible for memory allocation.
+ *
+ * The preferred interface is aio_timer_init. Use that
+ * unless you really need dynamic memory allocation.
+ *
+ * Returns: a pointer to the new timer
+ */
+static inline QEMUTimer *aio_timer_new(AioContext *ctx, QEMUClockType type,
+                                       int scale,
+                                       QEMUTimerCB *cb, void *opaque)
+{
+    return timer_new_tl(ctx->tlg.tl[type], scale, cb, opaque);
+}
+
+/**
+ * aio_timer_init:
+ * @ctx: the aio context
+ * @ts: the timer
+ * @type: the clock type
+ * @scale: the scale
+ * @cb: the callback to call on timer expiry
+ * @opaque: the opaque pointer to pass to the callback
+ *
+ * Initialise a new timer attached to the context @ctx.
+ * The caller is responsible for memory allocation.
+ */
+static inline void aio_timer_init(AioContext *ctx,
+                                  QEMUTimer *ts, QEMUClockType type,
+                                  int scale,
+                                  QEMUTimerCB *cb, void *opaque)
+{
+    timer_init_tl(ts, ctx->tlg.tl[type], scale, cb, opaque);
+}
+
+/**
+ * aio_compute_timeout:
+ * @ctx: the aio context
+ *
+ * Compute the timeout that a blocking aio_poll should use.
+ */
+int64_t aio_compute_timeout(AioContext *ctx);
+
+/**
+ * aio_disable_external:
+ * @ctx: the aio context
+ *
+ * Disable the further processing of external clients.
+ */
+static inline void aio_disable_external(AioContext *ctx)
+{
+    atomic_inc(&ctx->external_disable_cnt);
+}
+
+/**
+ * aio_enable_external:
+ * @ctx: the aio context
+ *
+ * Enable the processing of external clients.
+ */
+static inline void aio_enable_external(AioContext *ctx)
+{
+    assert(ctx->external_disable_cnt > 0);
+    atomic_dec(&ctx->external_disable_cnt);
+}
+
+/**
+ * aio_external_disabled:
+ * @ctx: the aio context
+ *
+ * Return true if the external clients are disabled.
+ */
+static inline bool aio_external_disabled(AioContext *ctx)
+{
+    return atomic_read(&ctx->external_disable_cnt);
+}
+
+/**
+ * aio_node_check:
+ * @ctx: the aio context
+ * @is_external: Whether or not the checked node is an external event source.
+ *
+ * Check if the node's is_external flag is okay to be polled by the ctx at this
+ * moment. True means green light.
+ */
+static inline bool aio_node_check(AioContext *ctx, bool is_external)
+{
+    return !is_external || !atomic_read(&ctx->external_disable_cnt);
+}
+
+/**
+ * aio_context_setup:
+ * @ctx: the aio context
+ *
+ * Initialize the aio context.
+ */
+void aio_context_setup(AioContext *ctx, Error **errp);
+
+#endif