aboutsummaryrefslogtreecommitdiff
path: root/include/block/aio.h
blob: 5743bf1ba07a6cab671af59bc748a4bc881b0c71 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
/*
 * 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-common.h"
#include "qemu/queue.h"
#include "qemu/event_notifier.h"
#include "qemu/thread.h"

typedef struct BlockDriverAIOCB BlockDriverAIOCB;
typedef void BlockDriverCompletionFunc(void *opaque, int ret);

typedef struct AIOCBInfo {
    void (*cancel)(BlockDriverAIOCB *acb);
    size_t aiocb_size;
} AIOCBInfo;

struct BlockDriverAIOCB {
    const AIOCBInfo *aiocb_info;
    BlockDriverState *bs;
    BlockDriverCompletionFunc *cb;
    void *opaque;
};

void *qemu_aio_get(const AIOCBInfo *aiocb_info, BlockDriverState *bs,
                   BlockDriverCompletionFunc *cb, void *opaque);
void qemu_aio_release(void *p);

typedef struct AioHandler AioHandler;
typedef void QEMUBHFunc(void *opaque);
typedef void IOHandler(void *opaque);

typedef struct AioContext {
    GSource source;

    /* 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;

    /* 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 for aio_notify.  */
    EventNotifier notifier;

    /* GPollFDs for aio_poll() */
    GArray *pollfds;

    /* Thread pool for performing work and receiving completion callbacks */
    struct ThreadPool *thread_pool;
} AioContext;

/**
 * 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(void);

/**
 * 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);

/**
 * 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_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.
 *
 * This is used internally in the implementation of the GSource.
 */
bool aio_pending(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.
 *
 * If there is no pending AIO operation or completion (bottom half),
 * return false.  If there are pending AIO operations of bottom halves,
 * return true.
 *
 * 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);

#ifdef CONFIG_POSIX
/* Register a file descriptor and associated callbacks.  Behaves very similarly
 * to qemu_set_fd_handler2.  Unlike qemu_set_fd_handler2, these callbacks will
 * be invoked when using qemu_aio_wait().
 *
 * 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,
                        IOHandler *io_read,
                        IOHandler *io_write,
                        void *opaque);
#endif

/* 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 qemu_aio_wait().
 *
 * 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);

/* 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);

/* Functions to operate on the main QEMU AioContext.  */

bool qemu_aio_wait(void);
void qemu_aio_set_event_notifier(EventNotifier *notifier,
                                 EventNotifierHandler *io_read);

#ifdef CONFIG_POSIX
void qemu_aio_set_fd_handler(int fd,
                             IOHandler *io_read,
                             IOHandler *io_write,
                             void *opaque);
#endif

#endif