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Commit | Line | Data |
---|---|---|
5c6c3a6c CH |
1 | /* |
2 | * Linux native AIO support. | |
3 | * | |
4 | * Copyright (C) 2009 IBM, Corp. | |
5 | * Copyright (C) 2009 Red Hat, Inc. | |
6 | * | |
7 | * This work is licensed under the terms of the GNU GPL, version 2 or later. | |
8 | * See the COPYING file in the top-level directory. | |
9 | */ | |
80c71a24 | 10 | #include "qemu/osdep.h" |
737e150e | 11 | #include "block/aio.h" |
1de7afc9 | 12 | #include "qemu/queue.h" |
2174f12b | 13 | #include "block/block.h" |
9f8540ec | 14 | #include "block/raw-aio.h" |
1de7afc9 | 15 | #include "qemu/event_notifier.h" |
2174f12b | 16 | #include "qemu/coroutine.h" |
ed6e2161 | 17 | #include "qapi/error.h" |
07668288 | 18 | #include "sysemu/block-backend.h" |
5c6c3a6c | 19 | |
ab50533b EGE |
20 | /* Only used for assertions. */ |
21 | #include "qemu/coroutine_int.h" | |
22 | ||
5c6c3a6c CH |
23 | #include <libaio.h> |
24 | ||
25 | /* | |
26 | * Queue size (per-device). | |
27 | * | |
28 | * XXX: eventually we need to communicate this to the guest and/or make it | |
29 | * tunable by the guest. If we get more outstanding requests at a time | |
30 | * than this we will get EAGAIN from io_submit which is communicated to | |
31 | * the guest as an I/O error. | |
32 | */ | |
2558cb8d | 33 | #define MAX_EVENTS 1024 |
5c6c3a6c | 34 | |
d7ddd0a1 SG |
35 | /* Maximum number of requests in a batch. (default value) */ |
36 | #define DEFAULT_MAX_BATCH 32 | |
37 | ||
5c6c3a6c | 38 | struct qemu_laiocb { |
2174f12b | 39 | Coroutine *co; |
dd7f7ed1 | 40 | LinuxAioState *ctx; |
5c6c3a6c CH |
41 | struct iocb iocb; |
42 | ssize_t ret; | |
43 | size_t nbytes; | |
b161e2e4 KW |
44 | QEMUIOVector *qiov; |
45 | bool is_read; | |
28b24087 | 46 | QSIMPLEQ_ENTRY(qemu_laiocb) next; |
5c6c3a6c CH |
47 | }; |
48 | ||
1b3abdcc | 49 | typedef struct { |
5e1b34a3 RP |
50 | unsigned int in_queue; |
51 | unsigned int in_flight; | |
43f2376e | 52 | bool blocked; |
28b24087 | 53 | QSIMPLEQ_HEAD(, qemu_laiocb) pending; |
1b3abdcc ML |
54 | } LaioQueue; |
55 | ||
dd7f7ed1 | 56 | struct LinuxAioState { |
0187f5c9 PB |
57 | AioContext *aio_context; |
58 | ||
5c6c3a6c | 59 | io_context_t ctx; |
c90caf25 | 60 | EventNotifier e; |
1b3abdcc | 61 | |
ab50533b | 62 | /* No locking required, only accessed from AioContext home thread */ |
1b3abdcc | 63 | LaioQueue io_q; |
2cdff7f6 | 64 | QEMUBH *completion_bh; |
2cdff7f6 SH |
65 | int event_idx; |
66 | int event_max; | |
5c6c3a6c CH |
67 | }; |
68 | ||
dd7f7ed1 | 69 | static void ioq_submit(LinuxAioState *s); |
28b24087 | 70 | |
5c6c3a6c CH |
71 | static inline ssize_t io_event_ret(struct io_event *ev) |
72 | { | |
73 | return (ssize_t)(((uint64_t)ev->res2 << 32) | ev->res); | |
74 | } | |
75 | ||
db0ffc24 | 76 | /* |
2b02fd81 | 77 | * Completes an AIO request. |
db0ffc24 | 78 | */ |
dd7f7ed1 | 79 | static void qemu_laio_process_completion(struct qemu_laiocb *laiocb) |
db0ffc24 KW |
80 | { |
81 | int ret; | |
82 | ||
db0ffc24 KW |
83 | ret = laiocb->ret; |
84 | if (ret != -ECANCELED) { | |
b161e2e4 | 85 | if (ret == laiocb->nbytes) { |
db0ffc24 | 86 | ret = 0; |
b161e2e4 KW |
87 | } else if (ret >= 0) { |
88 | /* Short reads mean EOF, pad with zeros. */ | |
89 | if (laiocb->is_read) { | |
3d9b4925 MT |
90 | qemu_iovec_memset(laiocb->qiov, ret, 0, |
91 | laiocb->qiov->size - ret); | |
b161e2e4 | 92 | } else { |
1c42f149 | 93 | ret = -ENOSPC; |
b161e2e4 KW |
94 | } |
95 | } | |
db0ffc24 KW |
96 | } |
97 | ||
2174f12b | 98 | laiocb->ret = ret; |
2b02fd81 JS |
99 | |
100 | /* | |
101 | * If the coroutine is already entered it must be in ioq_submit() and | |
102 | * will notice laio->ret has been filled in when it eventually runs | |
103 | * later. Coroutines cannot be entered recursively so avoid doing | |
104 | * that! | |
105 | */ | |
ab50533b | 106 | assert(laiocb->co->ctx == laiocb->ctx->aio_context); |
2b02fd81 JS |
107 | if (!qemu_coroutine_entered(laiocb->co)) { |
108 | aio_co_wake(laiocb->co); | |
2174f12b | 109 | } |
db0ffc24 KW |
110 | } |
111 | ||
9e909a58 RP |
112 | /** |
113 | * aio_ring buffer which is shared between userspace and kernel. | |
114 | * | |
115 | * This copied from linux/fs/aio.c, common header does not exist | |
116 | * but AIO exists for ages so we assume ABI is stable. | |
117 | */ | |
118 | struct aio_ring { | |
119 | unsigned id; /* kernel internal index number */ | |
120 | unsigned nr; /* number of io_events */ | |
121 | unsigned head; /* Written to by userland or by kernel. */ | |
122 | unsigned tail; | |
123 | ||
124 | unsigned magic; | |
125 | unsigned compat_features; | |
126 | unsigned incompat_features; | |
127 | unsigned header_length; /* size of aio_ring */ | |
128 | ||
f7795e40 | 129 | struct io_event io_events[]; |
9e909a58 RP |
130 | }; |
131 | ||
132 | /** | |
133 | * io_getevents_peek: | |
134 | * @ctx: AIO context | |
135 | * @events: pointer on events array, output value | |
136 | ||
137 | * Returns the number of completed events and sets a pointer | |
138 | * on events array. This function does not update the internal | |
139 | * ring buffer, only reads head and tail. When @events has been | |
140 | * processed io_getevents_commit() must be called. | |
141 | */ | |
142 | static inline unsigned int io_getevents_peek(io_context_t ctx, | |
143 | struct io_event **events) | |
144 | { | |
145 | struct aio_ring *ring = (struct aio_ring *)ctx; | |
146 | unsigned int head = ring->head, tail = ring->tail; | |
147 | unsigned int nr; | |
148 | ||
149 | nr = tail >= head ? tail - head : ring->nr - head; | |
150 | *events = ring->io_events + head; | |
151 | /* To avoid speculative loads of s->events[i] before observing tail. | |
152 | Paired with smp_wmb() inside linux/fs/aio.c: aio_complete(). */ | |
153 | smp_rmb(); | |
154 | ||
155 | return nr; | |
156 | } | |
157 | ||
158 | /** | |
159 | * io_getevents_commit: | |
160 | * @ctx: AIO context | |
161 | * @nr: the number of events on which head should be advanced | |
162 | * | |
163 | * Advances head of a ring buffer. | |
164 | */ | |
165 | static inline void io_getevents_commit(io_context_t ctx, unsigned int nr) | |
166 | { | |
167 | struct aio_ring *ring = (struct aio_ring *)ctx; | |
168 | ||
169 | if (nr) { | |
170 | ring->head = (ring->head + nr) % ring->nr; | |
171 | } | |
172 | } | |
173 | ||
174 | /** | |
175 | * io_getevents_advance_and_peek: | |
176 | * @ctx: AIO context | |
177 | * @events: pointer on events array, output value | |
178 | * @nr: the number of events on which head should be advanced | |
179 | * | |
180 | * Advances head of a ring buffer and returns number of elements left. | |
181 | */ | |
182 | static inline unsigned int | |
183 | io_getevents_advance_and_peek(io_context_t ctx, | |
184 | struct io_event **events, | |
185 | unsigned int nr) | |
186 | { | |
187 | io_getevents_commit(ctx, nr); | |
188 | return io_getevents_peek(ctx, events); | |
189 | } | |
190 | ||
3407de57 RP |
191 | /** |
192 | * qemu_laio_process_completions: | |
193 | * @s: AIO state | |
194 | * | |
195 | * Fetches completed I/O requests and invokes their callbacks. | |
2cdff7f6 SH |
196 | * |
197 | * The function is somewhat tricky because it supports nested event loops, for | |
198 | * example when a request callback invokes aio_poll(). In order to do this, | |
3407de57 RP |
199 | * indices are kept in LinuxAioState. Function schedules BH completion so it |
200 | * can be called again in a nested event loop. When there are no events left | |
201 | * to complete the BH is being canceled. | |
2cdff7f6 | 202 | */ |
3407de57 | 203 | static void qemu_laio_process_completions(LinuxAioState *s) |
5c6c3a6c | 204 | { |
9e909a58 | 205 | struct io_event *events; |
5c6c3a6c | 206 | |
2cdff7f6 SH |
207 | /* Reschedule so nested event loops see currently pending completions */ |
208 | qemu_bh_schedule(s->completion_bh); | |
5c6c3a6c | 209 | |
9e909a58 RP |
210 | while ((s->event_max = io_getevents_advance_and_peek(s->ctx, &events, |
211 | s->event_idx))) { | |
212 | for (s->event_idx = 0; s->event_idx < s->event_max; ) { | |
213 | struct iocb *iocb = events[s->event_idx].obj; | |
214 | struct qemu_laiocb *laiocb = | |
2cdff7f6 SH |
215 | container_of(iocb, struct qemu_laiocb, iocb); |
216 | ||
9e909a58 | 217 | laiocb->ret = io_event_ret(&events[s->event_idx]); |
2cdff7f6 | 218 | |
9e909a58 RP |
219 | /* Change counters one-by-one because we can be nested. */ |
220 | s->io_q.in_flight--; | |
221 | s->event_idx++; | |
222 | qemu_laio_process_completion(laiocb); | |
223 | } | |
2cdff7f6 | 224 | } |
28b24087 | 225 | |
9e909a58 RP |
226 | qemu_bh_cancel(s->completion_bh); |
227 | ||
228 | /* If we are nested we have to notify the level above that we are done | |
229 | * by setting event_max to zero, upper level will then jump out of it's | |
3202d8e4 | 230 | * own `for` loop. If we are the last all counters dropped to zero. */ |
9e909a58 RP |
231 | s->event_max = 0; |
232 | s->event_idx = 0; | |
3407de57 | 233 | } |
9e909a58 | 234 | |
3407de57 RP |
235 | static void qemu_laio_process_completions_and_submit(LinuxAioState *s) |
236 | { | |
237 | qemu_laio_process_completions(s); | |
1919631e | 238 | |
07668288 | 239 | if (!QSIMPLEQ_EMPTY(&s->io_q.pending)) { |
28b24087 PB |
240 | ioq_submit(s); |
241 | } | |
2cdff7f6 SH |
242 | } |
243 | ||
3407de57 RP |
244 | static void qemu_laio_completion_bh(void *opaque) |
245 | { | |
246 | LinuxAioState *s = opaque; | |
247 | ||
248 | qemu_laio_process_completions_and_submit(s); | |
249 | } | |
250 | ||
2cdff7f6 SH |
251 | static void qemu_laio_completion_cb(EventNotifier *e) |
252 | { | |
dd7f7ed1 | 253 | LinuxAioState *s = container_of(e, LinuxAioState, e); |
2cdff7f6 SH |
254 | |
255 | if (event_notifier_test_and_clear(&s->e)) { | |
3407de57 | 256 | qemu_laio_process_completions_and_submit(s); |
5c6c3a6c CH |
257 | } |
258 | } | |
259 | ||
ee686975 SH |
260 | static bool qemu_laio_poll_cb(void *opaque) |
261 | { | |
262 | EventNotifier *e = opaque; | |
263 | LinuxAioState *s = container_of(e, LinuxAioState, e); | |
264 | struct io_event *events; | |
265 | ||
826cc324 SH |
266 | return io_getevents_peek(s->ctx, &events); |
267 | } | |
268 | ||
269 | static void qemu_laio_poll_ready(EventNotifier *opaque) | |
270 | { | |
271 | EventNotifier *e = opaque; | |
272 | LinuxAioState *s = container_of(e, LinuxAioState, e); | |
ee686975 SH |
273 | |
274 | qemu_laio_process_completions_and_submit(s); | |
ee686975 SH |
275 | } |
276 | ||
1b3abdcc ML |
277 | static void ioq_init(LaioQueue *io_q) |
278 | { | |
28b24087 | 279 | QSIMPLEQ_INIT(&io_q->pending); |
5e1b34a3 RP |
280 | io_q->in_queue = 0; |
281 | io_q->in_flight = 0; | |
43f2376e | 282 | io_q->blocked = false; |
1b3abdcc ML |
283 | } |
284 | ||
dd7f7ed1 | 285 | static void ioq_submit(LinuxAioState *s) |
1b3abdcc | 286 | { |
82595da8 | 287 | int ret, len; |
28b24087 | 288 | struct qemu_laiocb *aiocb; |
5e1b34a3 | 289 | struct iocb *iocbs[MAX_EVENTS]; |
82595da8 | 290 | QSIMPLEQ_HEAD(, qemu_laiocb) completed; |
1b3abdcc | 291 | |
43f2376e | 292 | do { |
5e1b34a3 RP |
293 | if (s->io_q.in_flight >= MAX_EVENTS) { |
294 | break; | |
295 | } | |
43f2376e PB |
296 | len = 0; |
297 | QSIMPLEQ_FOREACH(aiocb, &s->io_q.pending, next) { | |
298 | iocbs[len++] = &aiocb->iocb; | |
5e1b34a3 | 299 | if (s->io_q.in_flight + len >= MAX_EVENTS) { |
43f2376e PB |
300 | break; |
301 | } | |
28b24087 | 302 | } |
1b3abdcc | 303 | |
43f2376e PB |
304 | ret = io_submit(s->ctx, len, iocbs); |
305 | if (ret == -EAGAIN) { | |
82595da8 | 306 | break; |
43f2376e PB |
307 | } |
308 | if (ret < 0) { | |
44713c9e KW |
309 | /* Fail the first request, retry the rest */ |
310 | aiocb = QSIMPLEQ_FIRST(&s->io_q.pending); | |
311 | QSIMPLEQ_REMOVE_HEAD(&s->io_q.pending, next); | |
312 | s->io_q.in_queue--; | |
313 | aiocb->ret = ret; | |
314 | qemu_laio_process_completion(aiocb); | |
315 | continue; | |
43f2376e PB |
316 | } |
317 | ||
5e1b34a3 RP |
318 | s->io_q.in_flight += ret; |
319 | s->io_q.in_queue -= ret; | |
82595da8 PB |
320 | aiocb = container_of(iocbs[ret - 1], struct qemu_laiocb, iocb); |
321 | QSIMPLEQ_SPLIT_AFTER(&s->io_q.pending, aiocb, next, &completed); | |
43f2376e | 322 | } while (ret == len && !QSIMPLEQ_EMPTY(&s->io_q.pending)); |
5e1b34a3 | 323 | s->io_q.blocked = (s->io_q.in_queue > 0); |
0ed93d84 RP |
324 | |
325 | if (s->io_q.in_flight) { | |
326 | /* We can try to complete something just right away if there are | |
327 | * still requests in-flight. */ | |
328 | qemu_laio_process_completions(s); | |
329 | /* | |
330 | * Even we have completed everything (in_flight == 0), the queue can | |
331 | * have still pended requests (in_queue > 0). We do not attempt to | |
332 | * repeat submission to avoid IO hang. The reason is simple: s->e is | |
333 | * still set and completion callback will be called shortly and all | |
334 | * pended requests will be submitted from there. | |
335 | */ | |
336 | } | |
1b3abdcc ML |
337 | } |
338 | ||
512da211 SG |
339 | static uint64_t laio_max_batch(LinuxAioState *s, uint64_t dev_max_batch) |
340 | { | |
341 | uint64_t max_batch = s->aio_context->aio_max_batch ?: DEFAULT_MAX_BATCH; | |
342 | ||
343 | /* | |
344 | * AIO context can be shared between multiple block devices, so | |
345 | * `dev_max_batch` allows reducing the batch size for latency-sensitive | |
346 | * devices. | |
347 | */ | |
348 | max_batch = MIN_NON_ZERO(dev_max_batch, max_batch); | |
349 | ||
350 | /* limit the batch with the number of available events */ | |
351 | max_batch = MIN_NON_ZERO(MAX_EVENTS - s->io_q.in_flight, max_batch); | |
352 | ||
353 | return max_batch; | |
354 | } | |
355 | ||
07668288 | 356 | static void laio_unplug_fn(void *opaque) |
1b3abdcc | 357 | { |
07668288 | 358 | LinuxAioState *s = opaque; |
f387cac5 | 359 | |
07668288 | 360 | if (!s->io_q.blocked && !QSIMPLEQ_EMPTY(&s->io_q.pending)) { |
de354644 | 361 | ioq_submit(s); |
1b3abdcc | 362 | } |
1b3abdcc ML |
363 | } |
364 | ||
2174f12b | 365 | static int laio_do_submit(int fd, struct qemu_laiocb *laiocb, off_t offset, |
512da211 | 366 | int type, uint64_t dev_max_batch) |
5c6c3a6c | 367 | { |
2174f12b KW |
368 | LinuxAioState *s = laiocb->ctx; |
369 | struct iocb *iocbs = &laiocb->iocb; | |
370 | QEMUIOVector *qiov = laiocb->qiov; | |
5c6c3a6c CH |
371 | |
372 | switch (type) { | |
373 | case QEMU_AIO_WRITE: | |
374 | io_prep_pwritev(iocbs, fd, qiov->iov, qiov->niov, offset); | |
7d37435b | 375 | break; |
4751d09a SL |
376 | case QEMU_AIO_ZONE_APPEND: |
377 | io_prep_pwritev(iocbs, fd, qiov->iov, qiov->niov, offset); | |
378 | break; | |
5c6c3a6c CH |
379 | case QEMU_AIO_READ: |
380 | io_prep_preadv(iocbs, fd, qiov->iov, qiov->niov, offset); | |
7d37435b | 381 | break; |
c30e624d | 382 | /* Currently Linux kernel does not support other operations */ |
5c6c3a6c CH |
383 | default: |
384 | fprintf(stderr, "%s: invalid AIO request type 0x%x.\n", | |
385 | __func__, type); | |
2174f12b | 386 | return -EIO; |
5c6c3a6c | 387 | } |
c90caf25 | 388 | io_set_eventfd(&laiocb->iocb, event_notifier_get_fd(&s->e)); |
5c6c3a6c | 389 | |
28b24087 | 390 | QSIMPLEQ_INSERT_TAIL(&s->io_q.pending, laiocb, next); |
5e1b34a3 | 391 | s->io_q.in_queue++; |
07668288 SH |
392 | if (!s->io_q.blocked) { |
393 | if (s->io_q.in_queue >= laio_max_batch(s, dev_max_batch)) { | |
394 | ioq_submit(s); | |
395 | } else { | |
396 | blk_io_plug_call(laio_unplug_fn, s); | |
397 | } | |
1b3abdcc | 398 | } |
5c6c3a6c | 399 | |
2174f12b KW |
400 | return 0; |
401 | } | |
402 | ||
ab50533b EGE |
403 | int coroutine_fn laio_co_submit(int fd, uint64_t offset, QEMUIOVector *qiov, |
404 | int type, uint64_t dev_max_batch) | |
2174f12b | 405 | { |
2174f12b | 406 | int ret; |
ab50533b | 407 | AioContext *ctx = qemu_get_current_aio_context(); |
2174f12b KW |
408 | struct qemu_laiocb laiocb = { |
409 | .co = qemu_coroutine_self(), | |
9d52aa3c | 410 | .nbytes = qiov->size, |
ab50533b | 411 | .ctx = aio_get_linux_aio(ctx), |
0ed93d84 | 412 | .ret = -EINPROGRESS, |
2174f12b KW |
413 | .is_read = (type == QEMU_AIO_READ), |
414 | .qiov = qiov, | |
415 | }; | |
416 | ||
512da211 | 417 | ret = laio_do_submit(fd, &laiocb, offset, type, dev_max_batch); |
2174f12b KW |
418 | if (ret < 0) { |
419 | return ret; | |
420 | } | |
421 | ||
0ed93d84 RP |
422 | if (laiocb.ret == -EINPROGRESS) { |
423 | qemu_coroutine_yield(); | |
424 | } | |
2174f12b KW |
425 | return laiocb.ret; |
426 | } | |
427 | ||
dd7f7ed1 | 428 | void laio_detach_aio_context(LinuxAioState *s, AioContext *old_context) |
c2f3426c | 429 | { |
60f782b6 | 430 | aio_set_event_notifier(old_context, &s->e, NULL, NULL, NULL); |
2cdff7f6 | 431 | qemu_bh_delete(s->completion_bh); |
1919631e | 432 | s->aio_context = NULL; |
c2f3426c SH |
433 | } |
434 | ||
dd7f7ed1 | 435 | void laio_attach_aio_context(LinuxAioState *s, AioContext *new_context) |
c2f3426c | 436 | { |
0187f5c9 | 437 | s->aio_context = new_context; |
2cdff7f6 | 438 | s->completion_bh = aio_bh_new(new_context, qemu_laio_completion_bh, s); |
60f782b6 | 439 | aio_set_event_notifier(new_context, &s->e, |
ee686975 | 440 | qemu_laio_completion_cb, |
826cc324 SH |
441 | qemu_laio_poll_cb, |
442 | qemu_laio_poll_ready); | |
c2f3426c SH |
443 | } |
444 | ||
ed6e2161 | 445 | LinuxAioState *laio_init(Error **errp) |
5c6c3a6c | 446 | { |
ed6e2161 | 447 | int rc; |
dd7f7ed1 | 448 | LinuxAioState *s; |
5c6c3a6c | 449 | |
7267c094 | 450 | s = g_malloc0(sizeof(*s)); |
ed6e2161 NA |
451 | rc = event_notifier_init(&s->e, false); |
452 | if (rc < 0) { | |
7a21bee2 | 453 | error_setg_errno(errp, -rc, "failed to initialize event notifier"); |
5c6c3a6c | 454 | goto out_free_state; |
c90caf25 | 455 | } |
5c6c3a6c | 456 | |
ed6e2161 NA |
457 | rc = io_setup(MAX_EVENTS, &s->ctx); |
458 | if (rc < 0) { | |
459 | error_setg_errno(errp, -rc, "failed to create linux AIO context"); | |
5c6c3a6c | 460 | goto out_close_efd; |
c90caf25 | 461 | } |
5c6c3a6c | 462 | |
1b3abdcc ML |
463 | ioq_init(&s->io_q); |
464 | ||
5c6c3a6c CH |
465 | return s; |
466 | ||
467 | out_close_efd: | |
c90caf25 | 468 | event_notifier_cleanup(&s->e); |
5c6c3a6c | 469 | out_free_state: |
7267c094 | 470 | g_free(s); |
5c6c3a6c CH |
471 | return NULL; |
472 | } | |
abd269b7 | 473 | |
dd7f7ed1 | 474 | void laio_cleanup(LinuxAioState *s) |
abd269b7 | 475 | { |
abd269b7 | 476 | event_notifier_cleanup(&s->e); |
a1abf40d GA |
477 | |
478 | if (io_destroy(s->ctx) != 0) { | |
479 | fprintf(stderr, "%s: destroy AIO context %p failed\n", | |
480 | __func__, &s->ctx); | |
481 | } | |
abd269b7 SH |
482 | g_free(s); |
483 | } |