spapr: Workaround for broken radix guests
[qemu.git] / block / io.c
1 /*
2 * Block layer I/O functions
3 *
4 * Copyright (c) 2003 Fabrice Bellard
5 *
6 * Permission is hereby granted, free of charge, to any person obtaining a copy
7 * of this software and associated documentation files (the "Software"), to deal
8 * in the Software without restriction, including without limitation the rights
9 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
10 * copies of the Software, and to permit persons to whom the Software is
11 * furnished to do so, subject to the following conditions:
12 *
13 * The above copyright notice and this permission notice shall be included in
14 * all copies or substantial portions of the Software.
15 *
16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
17 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
19 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
20 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
21 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
22 * THE SOFTWARE.
23 */
24
25 #include "qemu/osdep.h"
26 #include "trace.h"
27 #include "sysemu/block-backend.h"
28 #include "block/blockjob.h"
29 #include "block/block_int.h"
30 #include "qemu/cutils.h"
31 #include "qapi/error.h"
32 #include "qemu/error-report.h"
33
34 #define NOT_DONE 0x7fffffff /* used while emulated sync operation in progress */
35
36 static BlockAIOCB *bdrv_co_aio_prw_vector(BdrvChild *child,
37 int64_t offset,
38 QEMUIOVector *qiov,
39 BdrvRequestFlags flags,
40 BlockCompletionFunc *cb,
41 void *opaque,
42 bool is_write);
43 static void coroutine_fn bdrv_co_do_rw(void *opaque);
44 static int coroutine_fn bdrv_co_do_pwrite_zeroes(BlockDriverState *bs,
45 int64_t offset, int count, BdrvRequestFlags flags);
46
47 void bdrv_parent_drained_begin(BlockDriverState *bs)
48 {
49 BdrvChild *c;
50
51 QLIST_FOREACH(c, &bs->parents, next_parent) {
52 if (c->role->drained_begin) {
53 c->role->drained_begin(c);
54 }
55 }
56 }
57
58 void bdrv_parent_drained_end(BlockDriverState *bs)
59 {
60 BdrvChild *c;
61
62 QLIST_FOREACH(c, &bs->parents, next_parent) {
63 if (c->role->drained_end) {
64 c->role->drained_end(c);
65 }
66 }
67 }
68
69 static void bdrv_merge_limits(BlockLimits *dst, const BlockLimits *src)
70 {
71 dst->opt_transfer = MAX(dst->opt_transfer, src->opt_transfer);
72 dst->max_transfer = MIN_NON_ZERO(dst->max_transfer, src->max_transfer);
73 dst->opt_mem_alignment = MAX(dst->opt_mem_alignment,
74 src->opt_mem_alignment);
75 dst->min_mem_alignment = MAX(dst->min_mem_alignment,
76 src->min_mem_alignment);
77 dst->max_iov = MIN_NON_ZERO(dst->max_iov, src->max_iov);
78 }
79
80 void bdrv_refresh_limits(BlockDriverState *bs, Error **errp)
81 {
82 BlockDriver *drv = bs->drv;
83 Error *local_err = NULL;
84
85 memset(&bs->bl, 0, sizeof(bs->bl));
86
87 if (!drv) {
88 return;
89 }
90
91 /* Default alignment based on whether driver has byte interface */
92 bs->bl.request_alignment = drv->bdrv_co_preadv ? 1 : 512;
93
94 /* Take some limits from the children as a default */
95 if (bs->file) {
96 bdrv_refresh_limits(bs->file->bs, &local_err);
97 if (local_err) {
98 error_propagate(errp, local_err);
99 return;
100 }
101 bdrv_merge_limits(&bs->bl, &bs->file->bs->bl);
102 } else {
103 bs->bl.min_mem_alignment = 512;
104 bs->bl.opt_mem_alignment = getpagesize();
105
106 /* Safe default since most protocols use readv()/writev()/etc */
107 bs->bl.max_iov = IOV_MAX;
108 }
109
110 if (bs->backing) {
111 bdrv_refresh_limits(bs->backing->bs, &local_err);
112 if (local_err) {
113 error_propagate(errp, local_err);
114 return;
115 }
116 bdrv_merge_limits(&bs->bl, &bs->backing->bs->bl);
117 }
118
119 /* Then let the driver override it */
120 if (drv->bdrv_refresh_limits) {
121 drv->bdrv_refresh_limits(bs, errp);
122 }
123 }
124
125 /**
126 * The copy-on-read flag is actually a reference count so multiple users may
127 * use the feature without worrying about clobbering its previous state.
128 * Copy-on-read stays enabled until all users have called to disable it.
129 */
130 void bdrv_enable_copy_on_read(BlockDriverState *bs)
131 {
132 bs->copy_on_read++;
133 }
134
135 void bdrv_disable_copy_on_read(BlockDriverState *bs)
136 {
137 assert(bs->copy_on_read > 0);
138 bs->copy_on_read--;
139 }
140
141 /* Check if any requests are in-flight (including throttled requests) */
142 bool bdrv_requests_pending(BlockDriverState *bs)
143 {
144 BdrvChild *child;
145
146 if (atomic_read(&bs->in_flight)) {
147 return true;
148 }
149
150 QLIST_FOREACH(child, &bs->children, next) {
151 if (bdrv_requests_pending(child->bs)) {
152 return true;
153 }
154 }
155
156 return false;
157 }
158
159 static bool bdrv_drain_recurse(BlockDriverState *bs)
160 {
161 BdrvChild *child, *tmp;
162 bool waited;
163
164 waited = BDRV_POLL_WHILE(bs, atomic_read(&bs->in_flight) > 0);
165
166 if (bs->drv && bs->drv->bdrv_drain) {
167 bs->drv->bdrv_drain(bs);
168 }
169
170 QLIST_FOREACH_SAFE(child, &bs->children, next, tmp) {
171 BlockDriverState *bs = child->bs;
172 bool in_main_loop =
173 qemu_get_current_aio_context() == qemu_get_aio_context();
174 assert(bs->refcnt > 0);
175 if (in_main_loop) {
176 /* In case the recursive bdrv_drain_recurse processes a
177 * block_job_defer_to_main_loop BH and modifies the graph,
178 * let's hold a reference to bs until we are done.
179 *
180 * IOThread doesn't have such a BH, and it is not safe to call
181 * bdrv_unref without BQL, so skip doing it there.
182 */
183 bdrv_ref(bs);
184 }
185 waited |= bdrv_drain_recurse(bs);
186 if (in_main_loop) {
187 bdrv_unref(bs);
188 }
189 }
190
191 return waited;
192 }
193
194 typedef struct {
195 Coroutine *co;
196 BlockDriverState *bs;
197 bool done;
198 } BdrvCoDrainData;
199
200 static void bdrv_co_drain_bh_cb(void *opaque)
201 {
202 BdrvCoDrainData *data = opaque;
203 Coroutine *co = data->co;
204 BlockDriverState *bs = data->bs;
205
206 bdrv_dec_in_flight(bs);
207 bdrv_drained_begin(bs);
208 data->done = true;
209 aio_co_wake(co);
210 }
211
212 static void coroutine_fn bdrv_co_yield_to_drain(BlockDriverState *bs)
213 {
214 BdrvCoDrainData data;
215
216 /* Calling bdrv_drain() from a BH ensures the current coroutine yields and
217 * other coroutines run if they were queued from
218 * qemu_co_queue_run_restart(). */
219
220 assert(qemu_in_coroutine());
221 data = (BdrvCoDrainData) {
222 .co = qemu_coroutine_self(),
223 .bs = bs,
224 .done = false,
225 };
226 bdrv_inc_in_flight(bs);
227 aio_bh_schedule_oneshot(bdrv_get_aio_context(bs),
228 bdrv_co_drain_bh_cb, &data);
229
230 qemu_coroutine_yield();
231 /* If we are resumed from some other event (such as an aio completion or a
232 * timer callback), it is a bug in the caller that should be fixed. */
233 assert(data.done);
234 }
235
236 void bdrv_drained_begin(BlockDriverState *bs)
237 {
238 if (qemu_in_coroutine()) {
239 bdrv_co_yield_to_drain(bs);
240 return;
241 }
242
243 if (!bs->quiesce_counter++) {
244 aio_disable_external(bdrv_get_aio_context(bs));
245 bdrv_parent_drained_begin(bs);
246 }
247
248 bdrv_drain_recurse(bs);
249 }
250
251 void bdrv_drained_end(BlockDriverState *bs)
252 {
253 assert(bs->quiesce_counter > 0);
254 if (--bs->quiesce_counter > 0) {
255 return;
256 }
257
258 bdrv_parent_drained_end(bs);
259 aio_enable_external(bdrv_get_aio_context(bs));
260 }
261
262 /*
263 * Wait for pending requests to complete on a single BlockDriverState subtree,
264 * and suspend block driver's internal I/O until next request arrives.
265 *
266 * Note that unlike bdrv_drain_all(), the caller must hold the BlockDriverState
267 * AioContext.
268 *
269 * Only this BlockDriverState's AioContext is run, so in-flight requests must
270 * not depend on events in other AioContexts. In that case, use
271 * bdrv_drain_all() instead.
272 */
273 void coroutine_fn bdrv_co_drain(BlockDriverState *bs)
274 {
275 assert(qemu_in_coroutine());
276 bdrv_drained_begin(bs);
277 bdrv_drained_end(bs);
278 }
279
280 void bdrv_drain(BlockDriverState *bs)
281 {
282 bdrv_drained_begin(bs);
283 bdrv_drained_end(bs);
284 }
285
286 /*
287 * Wait for pending requests to complete across all BlockDriverStates
288 *
289 * This function does not flush data to disk, use bdrv_flush_all() for that
290 * after calling this function.
291 *
292 * This pauses all block jobs and disables external clients. It must
293 * be paired with bdrv_drain_all_end().
294 *
295 * NOTE: no new block jobs or BlockDriverStates can be created between
296 * the bdrv_drain_all_begin() and bdrv_drain_all_end() calls.
297 */
298 void bdrv_drain_all_begin(void)
299 {
300 /* Always run first iteration so any pending completion BHs run */
301 bool waited = true;
302 BlockDriverState *bs;
303 BdrvNextIterator it;
304 BlockJob *job = NULL;
305 GSList *aio_ctxs = NULL, *ctx;
306
307 while ((job = block_job_next(job))) {
308 AioContext *aio_context = blk_get_aio_context(job->blk);
309
310 aio_context_acquire(aio_context);
311 block_job_pause(job);
312 aio_context_release(aio_context);
313 }
314
315 for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
316 AioContext *aio_context = bdrv_get_aio_context(bs);
317
318 aio_context_acquire(aio_context);
319 bdrv_parent_drained_begin(bs);
320 aio_disable_external(aio_context);
321 aio_context_release(aio_context);
322
323 if (!g_slist_find(aio_ctxs, aio_context)) {
324 aio_ctxs = g_slist_prepend(aio_ctxs, aio_context);
325 }
326 }
327
328 /* Note that completion of an asynchronous I/O operation can trigger any
329 * number of other I/O operations on other devices---for example a
330 * coroutine can submit an I/O request to another device in response to
331 * request completion. Therefore we must keep looping until there was no
332 * more activity rather than simply draining each device independently.
333 */
334 while (waited) {
335 waited = false;
336
337 for (ctx = aio_ctxs; ctx != NULL; ctx = ctx->next) {
338 AioContext *aio_context = ctx->data;
339
340 aio_context_acquire(aio_context);
341 for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
342 if (aio_context == bdrv_get_aio_context(bs)) {
343 waited |= bdrv_drain_recurse(bs);
344 }
345 }
346 aio_context_release(aio_context);
347 }
348 }
349
350 g_slist_free(aio_ctxs);
351 }
352
353 void bdrv_drain_all_end(void)
354 {
355 BlockDriverState *bs;
356 BdrvNextIterator it;
357 BlockJob *job = NULL;
358
359 for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
360 AioContext *aio_context = bdrv_get_aio_context(bs);
361
362 aio_context_acquire(aio_context);
363 aio_enable_external(aio_context);
364 bdrv_parent_drained_end(bs);
365 aio_context_release(aio_context);
366 }
367
368 while ((job = block_job_next(job))) {
369 AioContext *aio_context = blk_get_aio_context(job->blk);
370
371 aio_context_acquire(aio_context);
372 block_job_resume(job);
373 aio_context_release(aio_context);
374 }
375 }
376
377 void bdrv_drain_all(void)
378 {
379 bdrv_drain_all_begin();
380 bdrv_drain_all_end();
381 }
382
383 /**
384 * Remove an active request from the tracked requests list
385 *
386 * This function should be called when a tracked request is completing.
387 */
388 static void tracked_request_end(BdrvTrackedRequest *req)
389 {
390 if (req->serialising) {
391 req->bs->serialising_in_flight--;
392 }
393
394 QLIST_REMOVE(req, list);
395 qemu_co_queue_restart_all(&req->wait_queue);
396 }
397
398 /**
399 * Add an active request to the tracked requests list
400 */
401 static void tracked_request_begin(BdrvTrackedRequest *req,
402 BlockDriverState *bs,
403 int64_t offset,
404 unsigned int bytes,
405 enum BdrvTrackedRequestType type)
406 {
407 *req = (BdrvTrackedRequest){
408 .bs = bs,
409 .offset = offset,
410 .bytes = bytes,
411 .type = type,
412 .co = qemu_coroutine_self(),
413 .serialising = false,
414 .overlap_offset = offset,
415 .overlap_bytes = bytes,
416 };
417
418 qemu_co_queue_init(&req->wait_queue);
419
420 QLIST_INSERT_HEAD(&bs->tracked_requests, req, list);
421 }
422
423 static void mark_request_serialising(BdrvTrackedRequest *req, uint64_t align)
424 {
425 int64_t overlap_offset = req->offset & ~(align - 1);
426 unsigned int overlap_bytes = ROUND_UP(req->offset + req->bytes, align)
427 - overlap_offset;
428
429 if (!req->serialising) {
430 req->bs->serialising_in_flight++;
431 req->serialising = true;
432 }
433
434 req->overlap_offset = MIN(req->overlap_offset, overlap_offset);
435 req->overlap_bytes = MAX(req->overlap_bytes, overlap_bytes);
436 }
437
438 /**
439 * Round a region to cluster boundaries (sector-based)
440 */
441 void bdrv_round_sectors_to_clusters(BlockDriverState *bs,
442 int64_t sector_num, int nb_sectors,
443 int64_t *cluster_sector_num,
444 int *cluster_nb_sectors)
445 {
446 BlockDriverInfo bdi;
447
448 if (bdrv_get_info(bs, &bdi) < 0 || bdi.cluster_size == 0) {
449 *cluster_sector_num = sector_num;
450 *cluster_nb_sectors = nb_sectors;
451 } else {
452 int64_t c = bdi.cluster_size / BDRV_SECTOR_SIZE;
453 *cluster_sector_num = QEMU_ALIGN_DOWN(sector_num, c);
454 *cluster_nb_sectors = QEMU_ALIGN_UP(sector_num - *cluster_sector_num +
455 nb_sectors, c);
456 }
457 }
458
459 /**
460 * Round a region to cluster boundaries
461 */
462 void bdrv_round_to_clusters(BlockDriverState *bs,
463 int64_t offset, unsigned int bytes,
464 int64_t *cluster_offset,
465 unsigned int *cluster_bytes)
466 {
467 BlockDriverInfo bdi;
468
469 if (bdrv_get_info(bs, &bdi) < 0 || bdi.cluster_size == 0) {
470 *cluster_offset = offset;
471 *cluster_bytes = bytes;
472 } else {
473 int64_t c = bdi.cluster_size;
474 *cluster_offset = QEMU_ALIGN_DOWN(offset, c);
475 *cluster_bytes = QEMU_ALIGN_UP(offset - *cluster_offset + bytes, c);
476 }
477 }
478
479 static int bdrv_get_cluster_size(BlockDriverState *bs)
480 {
481 BlockDriverInfo bdi;
482 int ret;
483
484 ret = bdrv_get_info(bs, &bdi);
485 if (ret < 0 || bdi.cluster_size == 0) {
486 return bs->bl.request_alignment;
487 } else {
488 return bdi.cluster_size;
489 }
490 }
491
492 static bool tracked_request_overlaps(BdrvTrackedRequest *req,
493 int64_t offset, unsigned int bytes)
494 {
495 /* aaaa bbbb */
496 if (offset >= req->overlap_offset + req->overlap_bytes) {
497 return false;
498 }
499 /* bbbb aaaa */
500 if (req->overlap_offset >= offset + bytes) {
501 return false;
502 }
503 return true;
504 }
505
506 void bdrv_inc_in_flight(BlockDriverState *bs)
507 {
508 atomic_inc(&bs->in_flight);
509 }
510
511 static void dummy_bh_cb(void *opaque)
512 {
513 }
514
515 void bdrv_wakeup(BlockDriverState *bs)
516 {
517 if (bs->wakeup) {
518 aio_bh_schedule_oneshot(qemu_get_aio_context(), dummy_bh_cb, NULL);
519 }
520 }
521
522 void bdrv_dec_in_flight(BlockDriverState *bs)
523 {
524 atomic_dec(&bs->in_flight);
525 bdrv_wakeup(bs);
526 }
527
528 static bool coroutine_fn wait_serialising_requests(BdrvTrackedRequest *self)
529 {
530 BlockDriverState *bs = self->bs;
531 BdrvTrackedRequest *req;
532 bool retry;
533 bool waited = false;
534
535 if (!bs->serialising_in_flight) {
536 return false;
537 }
538
539 do {
540 retry = false;
541 QLIST_FOREACH(req, &bs->tracked_requests, list) {
542 if (req == self || (!req->serialising && !self->serialising)) {
543 continue;
544 }
545 if (tracked_request_overlaps(req, self->overlap_offset,
546 self->overlap_bytes))
547 {
548 /* Hitting this means there was a reentrant request, for
549 * example, a block driver issuing nested requests. This must
550 * never happen since it means deadlock.
551 */
552 assert(qemu_coroutine_self() != req->co);
553
554 /* If the request is already (indirectly) waiting for us, or
555 * will wait for us as soon as it wakes up, then just go on
556 * (instead of producing a deadlock in the former case). */
557 if (!req->waiting_for) {
558 self->waiting_for = req;
559 qemu_co_queue_wait(&req->wait_queue, NULL);
560 self->waiting_for = NULL;
561 retry = true;
562 waited = true;
563 break;
564 }
565 }
566 }
567 } while (retry);
568
569 return waited;
570 }
571
572 static int bdrv_check_byte_request(BlockDriverState *bs, int64_t offset,
573 size_t size)
574 {
575 if (size > BDRV_REQUEST_MAX_SECTORS << BDRV_SECTOR_BITS) {
576 return -EIO;
577 }
578
579 if (!bdrv_is_inserted(bs)) {
580 return -ENOMEDIUM;
581 }
582
583 if (offset < 0) {
584 return -EIO;
585 }
586
587 return 0;
588 }
589
590 typedef struct RwCo {
591 BdrvChild *child;
592 int64_t offset;
593 QEMUIOVector *qiov;
594 bool is_write;
595 int ret;
596 BdrvRequestFlags flags;
597 } RwCo;
598
599 static void coroutine_fn bdrv_rw_co_entry(void *opaque)
600 {
601 RwCo *rwco = opaque;
602
603 if (!rwco->is_write) {
604 rwco->ret = bdrv_co_preadv(rwco->child, rwco->offset,
605 rwco->qiov->size, rwco->qiov,
606 rwco->flags);
607 } else {
608 rwco->ret = bdrv_co_pwritev(rwco->child, rwco->offset,
609 rwco->qiov->size, rwco->qiov,
610 rwco->flags);
611 }
612 }
613
614 /*
615 * Process a vectored synchronous request using coroutines
616 */
617 static int bdrv_prwv_co(BdrvChild *child, int64_t offset,
618 QEMUIOVector *qiov, bool is_write,
619 BdrvRequestFlags flags)
620 {
621 Coroutine *co;
622 RwCo rwco = {
623 .child = child,
624 .offset = offset,
625 .qiov = qiov,
626 .is_write = is_write,
627 .ret = NOT_DONE,
628 .flags = flags,
629 };
630
631 if (qemu_in_coroutine()) {
632 /* Fast-path if already in coroutine context */
633 bdrv_rw_co_entry(&rwco);
634 } else {
635 co = qemu_coroutine_create(bdrv_rw_co_entry, &rwco);
636 bdrv_coroutine_enter(child->bs, co);
637 BDRV_POLL_WHILE(child->bs, rwco.ret == NOT_DONE);
638 }
639 return rwco.ret;
640 }
641
642 /*
643 * Process a synchronous request using coroutines
644 */
645 static int bdrv_rw_co(BdrvChild *child, int64_t sector_num, uint8_t *buf,
646 int nb_sectors, bool is_write, BdrvRequestFlags flags)
647 {
648 QEMUIOVector qiov;
649 struct iovec iov = {
650 .iov_base = (void *)buf,
651 .iov_len = nb_sectors * BDRV_SECTOR_SIZE,
652 };
653
654 if (nb_sectors < 0 || nb_sectors > BDRV_REQUEST_MAX_SECTORS) {
655 return -EINVAL;
656 }
657
658 qemu_iovec_init_external(&qiov, &iov, 1);
659 return bdrv_prwv_co(child, sector_num << BDRV_SECTOR_BITS,
660 &qiov, is_write, flags);
661 }
662
663 /* return < 0 if error. See bdrv_write() for the return codes */
664 int bdrv_read(BdrvChild *child, int64_t sector_num,
665 uint8_t *buf, int nb_sectors)
666 {
667 return bdrv_rw_co(child, sector_num, buf, nb_sectors, false, 0);
668 }
669
670 /* Return < 0 if error. Important errors are:
671 -EIO generic I/O error (may happen for all errors)
672 -ENOMEDIUM No media inserted.
673 -EINVAL Invalid sector number or nb_sectors
674 -EACCES Trying to write a read-only device
675 */
676 int bdrv_write(BdrvChild *child, int64_t sector_num,
677 const uint8_t *buf, int nb_sectors)
678 {
679 return bdrv_rw_co(child, sector_num, (uint8_t *)buf, nb_sectors, true, 0);
680 }
681
682 int bdrv_pwrite_zeroes(BdrvChild *child, int64_t offset,
683 int count, BdrvRequestFlags flags)
684 {
685 QEMUIOVector qiov;
686 struct iovec iov = {
687 .iov_base = NULL,
688 .iov_len = count,
689 };
690
691 qemu_iovec_init_external(&qiov, &iov, 1);
692 return bdrv_prwv_co(child, offset, &qiov, true,
693 BDRV_REQ_ZERO_WRITE | flags);
694 }
695
696 /*
697 * Completely zero out a block device with the help of bdrv_pwrite_zeroes.
698 * The operation is sped up by checking the block status and only writing
699 * zeroes to the device if they currently do not return zeroes. Optional
700 * flags are passed through to bdrv_pwrite_zeroes (e.g. BDRV_REQ_MAY_UNMAP,
701 * BDRV_REQ_FUA).
702 *
703 * Returns < 0 on error, 0 on success. For error codes see bdrv_write().
704 */
705 int bdrv_make_zero(BdrvChild *child, BdrvRequestFlags flags)
706 {
707 int64_t target_sectors, ret, nb_sectors, sector_num = 0;
708 BlockDriverState *bs = child->bs;
709 BlockDriverState *file;
710 int n;
711
712 target_sectors = bdrv_nb_sectors(bs);
713 if (target_sectors < 0) {
714 return target_sectors;
715 }
716
717 for (;;) {
718 nb_sectors = MIN(target_sectors - sector_num, BDRV_REQUEST_MAX_SECTORS);
719 if (nb_sectors <= 0) {
720 return 0;
721 }
722 ret = bdrv_get_block_status(bs, sector_num, nb_sectors, &n, &file);
723 if (ret < 0) {
724 error_report("error getting block status at sector %" PRId64 ": %s",
725 sector_num, strerror(-ret));
726 return ret;
727 }
728 if (ret & BDRV_BLOCK_ZERO) {
729 sector_num += n;
730 continue;
731 }
732 ret = bdrv_pwrite_zeroes(child, sector_num << BDRV_SECTOR_BITS,
733 n << BDRV_SECTOR_BITS, flags);
734 if (ret < 0) {
735 error_report("error writing zeroes at sector %" PRId64 ": %s",
736 sector_num, strerror(-ret));
737 return ret;
738 }
739 sector_num += n;
740 }
741 }
742
743 int bdrv_preadv(BdrvChild *child, int64_t offset, QEMUIOVector *qiov)
744 {
745 int ret;
746
747 ret = bdrv_prwv_co(child, offset, qiov, false, 0);
748 if (ret < 0) {
749 return ret;
750 }
751
752 return qiov->size;
753 }
754
755 int bdrv_pread(BdrvChild *child, int64_t offset, void *buf, int bytes)
756 {
757 QEMUIOVector qiov;
758 struct iovec iov = {
759 .iov_base = (void *)buf,
760 .iov_len = bytes,
761 };
762
763 if (bytes < 0) {
764 return -EINVAL;
765 }
766
767 qemu_iovec_init_external(&qiov, &iov, 1);
768 return bdrv_preadv(child, offset, &qiov);
769 }
770
771 int bdrv_pwritev(BdrvChild *child, int64_t offset, QEMUIOVector *qiov)
772 {
773 int ret;
774
775 ret = bdrv_prwv_co(child, offset, qiov, true, 0);
776 if (ret < 0) {
777 return ret;
778 }
779
780 return qiov->size;
781 }
782
783 int bdrv_pwrite(BdrvChild *child, int64_t offset, const void *buf, int bytes)
784 {
785 QEMUIOVector qiov;
786 struct iovec iov = {
787 .iov_base = (void *) buf,
788 .iov_len = bytes,
789 };
790
791 if (bytes < 0) {
792 return -EINVAL;
793 }
794
795 qemu_iovec_init_external(&qiov, &iov, 1);
796 return bdrv_pwritev(child, offset, &qiov);
797 }
798
799 /*
800 * Writes to the file and ensures that no writes are reordered across this
801 * request (acts as a barrier)
802 *
803 * Returns 0 on success, -errno in error cases.
804 */
805 int bdrv_pwrite_sync(BdrvChild *child, int64_t offset,
806 const void *buf, int count)
807 {
808 int ret;
809
810 ret = bdrv_pwrite(child, offset, buf, count);
811 if (ret < 0) {
812 return ret;
813 }
814
815 ret = bdrv_flush(child->bs);
816 if (ret < 0) {
817 return ret;
818 }
819
820 return 0;
821 }
822
823 typedef struct CoroutineIOCompletion {
824 Coroutine *coroutine;
825 int ret;
826 } CoroutineIOCompletion;
827
828 static void bdrv_co_io_em_complete(void *opaque, int ret)
829 {
830 CoroutineIOCompletion *co = opaque;
831
832 co->ret = ret;
833 aio_co_wake(co->coroutine);
834 }
835
836 static int coroutine_fn bdrv_driver_preadv(BlockDriverState *bs,
837 uint64_t offset, uint64_t bytes,
838 QEMUIOVector *qiov, int flags)
839 {
840 BlockDriver *drv = bs->drv;
841 int64_t sector_num;
842 unsigned int nb_sectors;
843
844 assert(!(flags & ~BDRV_REQ_MASK));
845
846 if (drv->bdrv_co_preadv) {
847 return drv->bdrv_co_preadv(bs, offset, bytes, qiov, flags);
848 }
849
850 sector_num = offset >> BDRV_SECTOR_BITS;
851 nb_sectors = bytes >> BDRV_SECTOR_BITS;
852
853 assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0);
854 assert((bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
855 assert((bytes >> BDRV_SECTOR_BITS) <= BDRV_REQUEST_MAX_SECTORS);
856
857 if (drv->bdrv_co_readv) {
858 return drv->bdrv_co_readv(bs, sector_num, nb_sectors, qiov);
859 } else {
860 BlockAIOCB *acb;
861 CoroutineIOCompletion co = {
862 .coroutine = qemu_coroutine_self(),
863 };
864
865 acb = bs->drv->bdrv_aio_readv(bs, sector_num, qiov, nb_sectors,
866 bdrv_co_io_em_complete, &co);
867 if (acb == NULL) {
868 return -EIO;
869 } else {
870 qemu_coroutine_yield();
871 return co.ret;
872 }
873 }
874 }
875
876 static int coroutine_fn bdrv_driver_pwritev(BlockDriverState *bs,
877 uint64_t offset, uint64_t bytes,
878 QEMUIOVector *qiov, int flags)
879 {
880 BlockDriver *drv = bs->drv;
881 int64_t sector_num;
882 unsigned int nb_sectors;
883 int ret;
884
885 assert(!(flags & ~BDRV_REQ_MASK));
886
887 if (drv->bdrv_co_pwritev) {
888 ret = drv->bdrv_co_pwritev(bs, offset, bytes, qiov,
889 flags & bs->supported_write_flags);
890 flags &= ~bs->supported_write_flags;
891 goto emulate_flags;
892 }
893
894 sector_num = offset >> BDRV_SECTOR_BITS;
895 nb_sectors = bytes >> BDRV_SECTOR_BITS;
896
897 assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0);
898 assert((bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
899 assert((bytes >> BDRV_SECTOR_BITS) <= BDRV_REQUEST_MAX_SECTORS);
900
901 if (drv->bdrv_co_writev_flags) {
902 ret = drv->bdrv_co_writev_flags(bs, sector_num, nb_sectors, qiov,
903 flags & bs->supported_write_flags);
904 flags &= ~bs->supported_write_flags;
905 } else if (drv->bdrv_co_writev) {
906 assert(!bs->supported_write_flags);
907 ret = drv->bdrv_co_writev(bs, sector_num, nb_sectors, qiov);
908 } else {
909 BlockAIOCB *acb;
910 CoroutineIOCompletion co = {
911 .coroutine = qemu_coroutine_self(),
912 };
913
914 acb = bs->drv->bdrv_aio_writev(bs, sector_num, qiov, nb_sectors,
915 bdrv_co_io_em_complete, &co);
916 if (acb == NULL) {
917 ret = -EIO;
918 } else {
919 qemu_coroutine_yield();
920 ret = co.ret;
921 }
922 }
923
924 emulate_flags:
925 if (ret == 0 && (flags & BDRV_REQ_FUA)) {
926 ret = bdrv_co_flush(bs);
927 }
928
929 return ret;
930 }
931
932 static int coroutine_fn
933 bdrv_driver_pwritev_compressed(BlockDriverState *bs, uint64_t offset,
934 uint64_t bytes, QEMUIOVector *qiov)
935 {
936 BlockDriver *drv = bs->drv;
937
938 if (!drv->bdrv_co_pwritev_compressed) {
939 return -ENOTSUP;
940 }
941
942 return drv->bdrv_co_pwritev_compressed(bs, offset, bytes, qiov);
943 }
944
945 static int coroutine_fn bdrv_co_do_copy_on_readv(BdrvChild *child,
946 int64_t offset, unsigned int bytes, QEMUIOVector *qiov)
947 {
948 BlockDriverState *bs = child->bs;
949
950 /* Perform I/O through a temporary buffer so that users who scribble over
951 * their read buffer while the operation is in progress do not end up
952 * modifying the image file. This is critical for zero-copy guest I/O
953 * where anything might happen inside guest memory.
954 */
955 void *bounce_buffer;
956
957 BlockDriver *drv = bs->drv;
958 struct iovec iov;
959 QEMUIOVector bounce_qiov;
960 int64_t cluster_offset;
961 unsigned int cluster_bytes;
962 size_t skip_bytes;
963 int ret;
964
965 /* FIXME We cannot require callers to have write permissions when all they
966 * are doing is a read request. If we did things right, write permissions
967 * would be obtained anyway, but internally by the copy-on-read code. As
968 * long as it is implemented here rather than in a separat filter driver,
969 * the copy-on-read code doesn't have its own BdrvChild, however, for which
970 * it could request permissions. Therefore we have to bypass the permission
971 * system for the moment. */
972 // assert(child->perm & (BLK_PERM_WRITE_UNCHANGED | BLK_PERM_WRITE));
973
974 /* Cover entire cluster so no additional backing file I/O is required when
975 * allocating cluster in the image file.
976 */
977 bdrv_round_to_clusters(bs, offset, bytes, &cluster_offset, &cluster_bytes);
978
979 trace_bdrv_co_do_copy_on_readv(bs, offset, bytes,
980 cluster_offset, cluster_bytes);
981
982 iov.iov_len = cluster_bytes;
983 iov.iov_base = bounce_buffer = qemu_try_blockalign(bs, iov.iov_len);
984 if (bounce_buffer == NULL) {
985 ret = -ENOMEM;
986 goto err;
987 }
988
989 qemu_iovec_init_external(&bounce_qiov, &iov, 1);
990
991 ret = bdrv_driver_preadv(bs, cluster_offset, cluster_bytes,
992 &bounce_qiov, 0);
993 if (ret < 0) {
994 goto err;
995 }
996
997 if (drv->bdrv_co_pwrite_zeroes &&
998 buffer_is_zero(bounce_buffer, iov.iov_len)) {
999 /* FIXME: Should we (perhaps conditionally) be setting
1000 * BDRV_REQ_MAY_UNMAP, if it will allow for a sparser copy
1001 * that still correctly reads as zero? */
1002 ret = bdrv_co_do_pwrite_zeroes(bs, cluster_offset, cluster_bytes, 0);
1003 } else {
1004 /* This does not change the data on the disk, it is not necessary
1005 * to flush even in cache=writethrough mode.
1006 */
1007 ret = bdrv_driver_pwritev(bs, cluster_offset, cluster_bytes,
1008 &bounce_qiov, 0);
1009 }
1010
1011 if (ret < 0) {
1012 /* It might be okay to ignore write errors for guest requests. If this
1013 * is a deliberate copy-on-read then we don't want to ignore the error.
1014 * Simply report it in all cases.
1015 */
1016 goto err;
1017 }
1018
1019 skip_bytes = offset - cluster_offset;
1020 qemu_iovec_from_buf(qiov, 0, bounce_buffer + skip_bytes, bytes);
1021
1022 err:
1023 qemu_vfree(bounce_buffer);
1024 return ret;
1025 }
1026
1027 /*
1028 * Forwards an already correctly aligned request to the BlockDriver. This
1029 * handles copy on read, zeroing after EOF, and fragmentation of large
1030 * reads; any other features must be implemented by the caller.
1031 */
1032 static int coroutine_fn bdrv_aligned_preadv(BdrvChild *child,
1033 BdrvTrackedRequest *req, int64_t offset, unsigned int bytes,
1034 int64_t align, QEMUIOVector *qiov, int flags)
1035 {
1036 BlockDriverState *bs = child->bs;
1037 int64_t total_bytes, max_bytes;
1038 int ret = 0;
1039 uint64_t bytes_remaining = bytes;
1040 int max_transfer;
1041
1042 assert(is_power_of_2(align));
1043 assert((offset & (align - 1)) == 0);
1044 assert((bytes & (align - 1)) == 0);
1045 assert(!qiov || bytes == qiov->size);
1046 assert((bs->open_flags & BDRV_O_NO_IO) == 0);
1047 max_transfer = QEMU_ALIGN_DOWN(MIN_NON_ZERO(bs->bl.max_transfer, INT_MAX),
1048 align);
1049
1050 /* TODO: We would need a per-BDS .supported_read_flags and
1051 * potential fallback support, if we ever implement any read flags
1052 * to pass through to drivers. For now, there aren't any
1053 * passthrough flags. */
1054 assert(!(flags & ~(BDRV_REQ_NO_SERIALISING | BDRV_REQ_COPY_ON_READ)));
1055
1056 /* Handle Copy on Read and associated serialisation */
1057 if (flags & BDRV_REQ_COPY_ON_READ) {
1058 /* If we touch the same cluster it counts as an overlap. This
1059 * guarantees that allocating writes will be serialized and not race
1060 * with each other for the same cluster. For example, in copy-on-read
1061 * it ensures that the CoR read and write operations are atomic and
1062 * guest writes cannot interleave between them. */
1063 mark_request_serialising(req, bdrv_get_cluster_size(bs));
1064 }
1065
1066 if (!(flags & BDRV_REQ_NO_SERIALISING)) {
1067 wait_serialising_requests(req);
1068 }
1069
1070 if (flags & BDRV_REQ_COPY_ON_READ) {
1071 int64_t start_sector = offset >> BDRV_SECTOR_BITS;
1072 int64_t end_sector = DIV_ROUND_UP(offset + bytes, BDRV_SECTOR_SIZE);
1073 unsigned int nb_sectors = end_sector - start_sector;
1074 int pnum;
1075
1076 ret = bdrv_is_allocated(bs, start_sector, nb_sectors, &pnum);
1077 if (ret < 0) {
1078 goto out;
1079 }
1080
1081 if (!ret || pnum != nb_sectors) {
1082 ret = bdrv_co_do_copy_on_readv(child, offset, bytes, qiov);
1083 goto out;
1084 }
1085 }
1086
1087 /* Forward the request to the BlockDriver, possibly fragmenting it */
1088 total_bytes = bdrv_getlength(bs);
1089 if (total_bytes < 0) {
1090 ret = total_bytes;
1091 goto out;
1092 }
1093
1094 max_bytes = ROUND_UP(MAX(0, total_bytes - offset), align);
1095 if (bytes <= max_bytes && bytes <= max_transfer) {
1096 ret = bdrv_driver_preadv(bs, offset, bytes, qiov, 0);
1097 goto out;
1098 }
1099
1100 while (bytes_remaining) {
1101 int num;
1102
1103 if (max_bytes) {
1104 QEMUIOVector local_qiov;
1105
1106 num = MIN(bytes_remaining, MIN(max_bytes, max_transfer));
1107 assert(num);
1108 qemu_iovec_init(&local_qiov, qiov->niov);
1109 qemu_iovec_concat(&local_qiov, qiov, bytes - bytes_remaining, num);
1110
1111 ret = bdrv_driver_preadv(bs, offset + bytes - bytes_remaining,
1112 num, &local_qiov, 0);
1113 max_bytes -= num;
1114 qemu_iovec_destroy(&local_qiov);
1115 } else {
1116 num = bytes_remaining;
1117 ret = qemu_iovec_memset(qiov, bytes - bytes_remaining, 0,
1118 bytes_remaining);
1119 }
1120 if (ret < 0) {
1121 goto out;
1122 }
1123 bytes_remaining -= num;
1124 }
1125
1126 out:
1127 return ret < 0 ? ret : 0;
1128 }
1129
1130 /*
1131 * Handle a read request in coroutine context
1132 */
1133 int coroutine_fn bdrv_co_preadv(BdrvChild *child,
1134 int64_t offset, unsigned int bytes, QEMUIOVector *qiov,
1135 BdrvRequestFlags flags)
1136 {
1137 BlockDriverState *bs = child->bs;
1138 BlockDriver *drv = bs->drv;
1139 BdrvTrackedRequest req;
1140
1141 uint64_t align = bs->bl.request_alignment;
1142 uint8_t *head_buf = NULL;
1143 uint8_t *tail_buf = NULL;
1144 QEMUIOVector local_qiov;
1145 bool use_local_qiov = false;
1146 int ret;
1147
1148 if (!drv) {
1149 return -ENOMEDIUM;
1150 }
1151
1152 ret = bdrv_check_byte_request(bs, offset, bytes);
1153 if (ret < 0) {
1154 return ret;
1155 }
1156
1157 bdrv_inc_in_flight(bs);
1158
1159 /* Don't do copy-on-read if we read data before write operation */
1160 if (bs->copy_on_read && !(flags & BDRV_REQ_NO_SERIALISING)) {
1161 flags |= BDRV_REQ_COPY_ON_READ;
1162 }
1163
1164 /* Align read if necessary by padding qiov */
1165 if (offset & (align - 1)) {
1166 head_buf = qemu_blockalign(bs, align);
1167 qemu_iovec_init(&local_qiov, qiov->niov + 2);
1168 qemu_iovec_add(&local_qiov, head_buf, offset & (align - 1));
1169 qemu_iovec_concat(&local_qiov, qiov, 0, qiov->size);
1170 use_local_qiov = true;
1171
1172 bytes += offset & (align - 1);
1173 offset = offset & ~(align - 1);
1174 }
1175
1176 if ((offset + bytes) & (align - 1)) {
1177 if (!use_local_qiov) {
1178 qemu_iovec_init(&local_qiov, qiov->niov + 1);
1179 qemu_iovec_concat(&local_qiov, qiov, 0, qiov->size);
1180 use_local_qiov = true;
1181 }
1182 tail_buf = qemu_blockalign(bs, align);
1183 qemu_iovec_add(&local_qiov, tail_buf,
1184 align - ((offset + bytes) & (align - 1)));
1185
1186 bytes = ROUND_UP(bytes, align);
1187 }
1188
1189 tracked_request_begin(&req, bs, offset, bytes, BDRV_TRACKED_READ);
1190 ret = bdrv_aligned_preadv(child, &req, offset, bytes, align,
1191 use_local_qiov ? &local_qiov : qiov,
1192 flags);
1193 tracked_request_end(&req);
1194 bdrv_dec_in_flight(bs);
1195
1196 if (use_local_qiov) {
1197 qemu_iovec_destroy(&local_qiov);
1198 qemu_vfree(head_buf);
1199 qemu_vfree(tail_buf);
1200 }
1201
1202 return ret;
1203 }
1204
1205 static int coroutine_fn bdrv_co_do_readv(BdrvChild *child,
1206 int64_t sector_num, int nb_sectors, QEMUIOVector *qiov,
1207 BdrvRequestFlags flags)
1208 {
1209 if (nb_sectors < 0 || nb_sectors > BDRV_REQUEST_MAX_SECTORS) {
1210 return -EINVAL;
1211 }
1212
1213 return bdrv_co_preadv(child, sector_num << BDRV_SECTOR_BITS,
1214 nb_sectors << BDRV_SECTOR_BITS, qiov, flags);
1215 }
1216
1217 int coroutine_fn bdrv_co_readv(BdrvChild *child, int64_t sector_num,
1218 int nb_sectors, QEMUIOVector *qiov)
1219 {
1220 trace_bdrv_co_readv(child->bs, sector_num, nb_sectors);
1221
1222 return bdrv_co_do_readv(child, sector_num, nb_sectors, qiov, 0);
1223 }
1224
1225 /* Maximum buffer for write zeroes fallback, in bytes */
1226 #define MAX_WRITE_ZEROES_BOUNCE_BUFFER (32768 << BDRV_SECTOR_BITS)
1227
1228 static int coroutine_fn bdrv_co_do_pwrite_zeroes(BlockDriverState *bs,
1229 int64_t offset, int count, BdrvRequestFlags flags)
1230 {
1231 BlockDriver *drv = bs->drv;
1232 QEMUIOVector qiov;
1233 struct iovec iov = {0};
1234 int ret = 0;
1235 bool need_flush = false;
1236 int head = 0;
1237 int tail = 0;
1238
1239 int max_write_zeroes = MIN_NON_ZERO(bs->bl.max_pwrite_zeroes, INT_MAX);
1240 int alignment = MAX(bs->bl.pwrite_zeroes_alignment,
1241 bs->bl.request_alignment);
1242 int max_transfer = MIN_NON_ZERO(bs->bl.max_transfer,
1243 MAX_WRITE_ZEROES_BOUNCE_BUFFER);
1244
1245 assert(alignment % bs->bl.request_alignment == 0);
1246 head = offset % alignment;
1247 tail = (offset + count) % alignment;
1248 max_write_zeroes = QEMU_ALIGN_DOWN(max_write_zeroes, alignment);
1249 assert(max_write_zeroes >= bs->bl.request_alignment);
1250
1251 while (count > 0 && !ret) {
1252 int num = count;
1253
1254 /* Align request. Block drivers can expect the "bulk" of the request
1255 * to be aligned, and that unaligned requests do not cross cluster
1256 * boundaries.
1257 */
1258 if (head) {
1259 /* Make a small request up to the first aligned sector. For
1260 * convenience, limit this request to max_transfer even if
1261 * we don't need to fall back to writes. */
1262 num = MIN(MIN(count, max_transfer), alignment - head);
1263 head = (head + num) % alignment;
1264 assert(num < max_write_zeroes);
1265 } else if (tail && num > alignment) {
1266 /* Shorten the request to the last aligned sector. */
1267 num -= tail;
1268 }
1269
1270 /* limit request size */
1271 if (num > max_write_zeroes) {
1272 num = max_write_zeroes;
1273 }
1274
1275 ret = -ENOTSUP;
1276 /* First try the efficient write zeroes operation */
1277 if (drv->bdrv_co_pwrite_zeroes) {
1278 ret = drv->bdrv_co_pwrite_zeroes(bs, offset, num,
1279 flags & bs->supported_zero_flags);
1280 if (ret != -ENOTSUP && (flags & BDRV_REQ_FUA) &&
1281 !(bs->supported_zero_flags & BDRV_REQ_FUA)) {
1282 need_flush = true;
1283 }
1284 } else {
1285 assert(!bs->supported_zero_flags);
1286 }
1287
1288 if (ret == -ENOTSUP) {
1289 /* Fall back to bounce buffer if write zeroes is unsupported */
1290 BdrvRequestFlags write_flags = flags & ~BDRV_REQ_ZERO_WRITE;
1291
1292 if ((flags & BDRV_REQ_FUA) &&
1293 !(bs->supported_write_flags & BDRV_REQ_FUA)) {
1294 /* No need for bdrv_driver_pwrite() to do a fallback
1295 * flush on each chunk; use just one at the end */
1296 write_flags &= ~BDRV_REQ_FUA;
1297 need_flush = true;
1298 }
1299 num = MIN(num, max_transfer);
1300 iov.iov_len = num;
1301 if (iov.iov_base == NULL) {
1302 iov.iov_base = qemu_try_blockalign(bs, num);
1303 if (iov.iov_base == NULL) {
1304 ret = -ENOMEM;
1305 goto fail;
1306 }
1307 memset(iov.iov_base, 0, num);
1308 }
1309 qemu_iovec_init_external(&qiov, &iov, 1);
1310
1311 ret = bdrv_driver_pwritev(bs, offset, num, &qiov, write_flags);
1312
1313 /* Keep bounce buffer around if it is big enough for all
1314 * all future requests.
1315 */
1316 if (num < max_transfer) {
1317 qemu_vfree(iov.iov_base);
1318 iov.iov_base = NULL;
1319 }
1320 }
1321
1322 offset += num;
1323 count -= num;
1324 }
1325
1326 fail:
1327 if (ret == 0 && need_flush) {
1328 ret = bdrv_co_flush(bs);
1329 }
1330 qemu_vfree(iov.iov_base);
1331 return ret;
1332 }
1333
1334 /*
1335 * Forwards an already correctly aligned write request to the BlockDriver,
1336 * after possibly fragmenting it.
1337 */
1338 static int coroutine_fn bdrv_aligned_pwritev(BdrvChild *child,
1339 BdrvTrackedRequest *req, int64_t offset, unsigned int bytes,
1340 int64_t align, QEMUIOVector *qiov, int flags)
1341 {
1342 BlockDriverState *bs = child->bs;
1343 BlockDriver *drv = bs->drv;
1344 bool waited;
1345 int ret;
1346
1347 int64_t start_sector = offset >> BDRV_SECTOR_BITS;
1348 int64_t end_sector = DIV_ROUND_UP(offset + bytes, BDRV_SECTOR_SIZE);
1349 uint64_t bytes_remaining = bytes;
1350 int max_transfer;
1351
1352 assert(is_power_of_2(align));
1353 assert((offset & (align - 1)) == 0);
1354 assert((bytes & (align - 1)) == 0);
1355 assert(!qiov || bytes == qiov->size);
1356 assert((bs->open_flags & BDRV_O_NO_IO) == 0);
1357 assert(!(flags & ~BDRV_REQ_MASK));
1358 max_transfer = QEMU_ALIGN_DOWN(MIN_NON_ZERO(bs->bl.max_transfer, INT_MAX),
1359 align);
1360
1361 waited = wait_serialising_requests(req);
1362 assert(!waited || !req->serialising);
1363 assert(req->overlap_offset <= offset);
1364 assert(offset + bytes <= req->overlap_offset + req->overlap_bytes);
1365 /* FIXME: Block migration uses the BlockBackend of the guest device at a
1366 * point when it has not yet taken write permissions. This will be
1367 * fixed by a future patch, but for now we have to bypass this
1368 * assertion for block migration to work. */
1369 // assert(child->perm & BLK_PERM_WRITE);
1370 /* FIXME: Because of the above, we also cannot guarantee that all format
1371 * BDS take the BLK_PERM_RESIZE permission on their file BDS, since
1372 * they are not obligated to do so if they do not have any parent
1373 * that has taken the permission to write to them. */
1374 // assert(end_sector <= bs->total_sectors || child->perm & BLK_PERM_RESIZE);
1375
1376 ret = notifier_with_return_list_notify(&bs->before_write_notifiers, req);
1377
1378 if (!ret && bs->detect_zeroes != BLOCKDEV_DETECT_ZEROES_OPTIONS_OFF &&
1379 !(flags & BDRV_REQ_ZERO_WRITE) && drv->bdrv_co_pwrite_zeroes &&
1380 qemu_iovec_is_zero(qiov)) {
1381 flags |= BDRV_REQ_ZERO_WRITE;
1382 if (bs->detect_zeroes == BLOCKDEV_DETECT_ZEROES_OPTIONS_UNMAP) {
1383 flags |= BDRV_REQ_MAY_UNMAP;
1384 }
1385 }
1386
1387 if (ret < 0) {
1388 /* Do nothing, write notifier decided to fail this request */
1389 } else if (flags & BDRV_REQ_ZERO_WRITE) {
1390 bdrv_debug_event(bs, BLKDBG_PWRITEV_ZERO);
1391 ret = bdrv_co_do_pwrite_zeroes(bs, offset, bytes, flags);
1392 } else if (flags & BDRV_REQ_WRITE_COMPRESSED) {
1393 ret = bdrv_driver_pwritev_compressed(bs, offset, bytes, qiov);
1394 } else if (bytes <= max_transfer) {
1395 bdrv_debug_event(bs, BLKDBG_PWRITEV);
1396 ret = bdrv_driver_pwritev(bs, offset, bytes, qiov, flags);
1397 } else {
1398 bdrv_debug_event(bs, BLKDBG_PWRITEV);
1399 while (bytes_remaining) {
1400 int num = MIN(bytes_remaining, max_transfer);
1401 QEMUIOVector local_qiov;
1402 int local_flags = flags;
1403
1404 assert(num);
1405 if (num < bytes_remaining && (flags & BDRV_REQ_FUA) &&
1406 !(bs->supported_write_flags & BDRV_REQ_FUA)) {
1407 /* If FUA is going to be emulated by flush, we only
1408 * need to flush on the last iteration */
1409 local_flags &= ~BDRV_REQ_FUA;
1410 }
1411 qemu_iovec_init(&local_qiov, qiov->niov);
1412 qemu_iovec_concat(&local_qiov, qiov, bytes - bytes_remaining, num);
1413
1414 ret = bdrv_driver_pwritev(bs, offset + bytes - bytes_remaining,
1415 num, &local_qiov, local_flags);
1416 qemu_iovec_destroy(&local_qiov);
1417 if (ret < 0) {
1418 break;
1419 }
1420 bytes_remaining -= num;
1421 }
1422 }
1423 bdrv_debug_event(bs, BLKDBG_PWRITEV_DONE);
1424
1425 ++bs->write_gen;
1426 bdrv_set_dirty(bs, start_sector, end_sector - start_sector);
1427
1428 if (bs->wr_highest_offset < offset + bytes) {
1429 bs->wr_highest_offset = offset + bytes;
1430 }
1431
1432 if (ret >= 0) {
1433 bs->total_sectors = MAX(bs->total_sectors, end_sector);
1434 ret = 0;
1435 }
1436
1437 return ret;
1438 }
1439
1440 static int coroutine_fn bdrv_co_do_zero_pwritev(BdrvChild *child,
1441 int64_t offset,
1442 unsigned int bytes,
1443 BdrvRequestFlags flags,
1444 BdrvTrackedRequest *req)
1445 {
1446 BlockDriverState *bs = child->bs;
1447 uint8_t *buf = NULL;
1448 QEMUIOVector local_qiov;
1449 struct iovec iov;
1450 uint64_t align = bs->bl.request_alignment;
1451 unsigned int head_padding_bytes, tail_padding_bytes;
1452 int ret = 0;
1453
1454 head_padding_bytes = offset & (align - 1);
1455 tail_padding_bytes = align - ((offset + bytes) & (align - 1));
1456
1457
1458 assert(flags & BDRV_REQ_ZERO_WRITE);
1459 if (head_padding_bytes || tail_padding_bytes) {
1460 buf = qemu_blockalign(bs, align);
1461 iov = (struct iovec) {
1462 .iov_base = buf,
1463 .iov_len = align,
1464 };
1465 qemu_iovec_init_external(&local_qiov, &iov, 1);
1466 }
1467 if (head_padding_bytes) {
1468 uint64_t zero_bytes = MIN(bytes, align - head_padding_bytes);
1469
1470 /* RMW the unaligned part before head. */
1471 mark_request_serialising(req, align);
1472 wait_serialising_requests(req);
1473 bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_HEAD);
1474 ret = bdrv_aligned_preadv(child, req, offset & ~(align - 1), align,
1475 align, &local_qiov, 0);
1476 if (ret < 0) {
1477 goto fail;
1478 }
1479 bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_HEAD);
1480
1481 memset(buf + head_padding_bytes, 0, zero_bytes);
1482 ret = bdrv_aligned_pwritev(child, req, offset & ~(align - 1), align,
1483 align, &local_qiov,
1484 flags & ~BDRV_REQ_ZERO_WRITE);
1485 if (ret < 0) {
1486 goto fail;
1487 }
1488 offset += zero_bytes;
1489 bytes -= zero_bytes;
1490 }
1491
1492 assert(!bytes || (offset & (align - 1)) == 0);
1493 if (bytes >= align) {
1494 /* Write the aligned part in the middle. */
1495 uint64_t aligned_bytes = bytes & ~(align - 1);
1496 ret = bdrv_aligned_pwritev(child, req, offset, aligned_bytes, align,
1497 NULL, flags);
1498 if (ret < 0) {
1499 goto fail;
1500 }
1501 bytes -= aligned_bytes;
1502 offset += aligned_bytes;
1503 }
1504
1505 assert(!bytes || (offset & (align - 1)) == 0);
1506 if (bytes) {
1507 assert(align == tail_padding_bytes + bytes);
1508 /* RMW the unaligned part after tail. */
1509 mark_request_serialising(req, align);
1510 wait_serialising_requests(req);
1511 bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_TAIL);
1512 ret = bdrv_aligned_preadv(child, req, offset, align,
1513 align, &local_qiov, 0);
1514 if (ret < 0) {
1515 goto fail;
1516 }
1517 bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_TAIL);
1518
1519 memset(buf, 0, bytes);
1520 ret = bdrv_aligned_pwritev(child, req, offset, align, align,
1521 &local_qiov, flags & ~BDRV_REQ_ZERO_WRITE);
1522 }
1523 fail:
1524 qemu_vfree(buf);
1525 return ret;
1526
1527 }
1528
1529 /*
1530 * Handle a write request in coroutine context
1531 */
1532 int coroutine_fn bdrv_co_pwritev(BdrvChild *child,
1533 int64_t offset, unsigned int bytes, QEMUIOVector *qiov,
1534 BdrvRequestFlags flags)
1535 {
1536 BlockDriverState *bs = child->bs;
1537 BdrvTrackedRequest req;
1538 uint64_t align = bs->bl.request_alignment;
1539 uint8_t *head_buf = NULL;
1540 uint8_t *tail_buf = NULL;
1541 QEMUIOVector local_qiov;
1542 bool use_local_qiov = false;
1543 int ret;
1544
1545 if (!bs->drv) {
1546 return -ENOMEDIUM;
1547 }
1548 if (bs->read_only) {
1549 return -EPERM;
1550 }
1551 assert(!(bs->open_flags & BDRV_O_INACTIVE));
1552
1553 ret = bdrv_check_byte_request(bs, offset, bytes);
1554 if (ret < 0) {
1555 return ret;
1556 }
1557
1558 bdrv_inc_in_flight(bs);
1559 /*
1560 * Align write if necessary by performing a read-modify-write cycle.
1561 * Pad qiov with the read parts and be sure to have a tracked request not
1562 * only for bdrv_aligned_pwritev, but also for the reads of the RMW cycle.
1563 */
1564 tracked_request_begin(&req, bs, offset, bytes, BDRV_TRACKED_WRITE);
1565
1566 if (!qiov) {
1567 ret = bdrv_co_do_zero_pwritev(child, offset, bytes, flags, &req);
1568 goto out;
1569 }
1570
1571 if (offset & (align - 1)) {
1572 QEMUIOVector head_qiov;
1573 struct iovec head_iov;
1574
1575 mark_request_serialising(&req, align);
1576 wait_serialising_requests(&req);
1577
1578 head_buf = qemu_blockalign(bs, align);
1579 head_iov = (struct iovec) {
1580 .iov_base = head_buf,
1581 .iov_len = align,
1582 };
1583 qemu_iovec_init_external(&head_qiov, &head_iov, 1);
1584
1585 bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_HEAD);
1586 ret = bdrv_aligned_preadv(child, &req, offset & ~(align - 1), align,
1587 align, &head_qiov, 0);
1588 if (ret < 0) {
1589 goto fail;
1590 }
1591 bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_HEAD);
1592
1593 qemu_iovec_init(&local_qiov, qiov->niov + 2);
1594 qemu_iovec_add(&local_qiov, head_buf, offset & (align - 1));
1595 qemu_iovec_concat(&local_qiov, qiov, 0, qiov->size);
1596 use_local_qiov = true;
1597
1598 bytes += offset & (align - 1);
1599 offset = offset & ~(align - 1);
1600
1601 /* We have read the tail already if the request is smaller
1602 * than one aligned block.
1603 */
1604 if (bytes < align) {
1605 qemu_iovec_add(&local_qiov, head_buf + bytes, align - bytes);
1606 bytes = align;
1607 }
1608 }
1609
1610 if ((offset + bytes) & (align - 1)) {
1611 QEMUIOVector tail_qiov;
1612 struct iovec tail_iov;
1613 size_t tail_bytes;
1614 bool waited;
1615
1616 mark_request_serialising(&req, align);
1617 waited = wait_serialising_requests(&req);
1618 assert(!waited || !use_local_qiov);
1619
1620 tail_buf = qemu_blockalign(bs, align);
1621 tail_iov = (struct iovec) {
1622 .iov_base = tail_buf,
1623 .iov_len = align,
1624 };
1625 qemu_iovec_init_external(&tail_qiov, &tail_iov, 1);
1626
1627 bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_TAIL);
1628 ret = bdrv_aligned_preadv(child, &req, (offset + bytes) & ~(align - 1),
1629 align, align, &tail_qiov, 0);
1630 if (ret < 0) {
1631 goto fail;
1632 }
1633 bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_TAIL);
1634
1635 if (!use_local_qiov) {
1636 qemu_iovec_init(&local_qiov, qiov->niov + 1);
1637 qemu_iovec_concat(&local_qiov, qiov, 0, qiov->size);
1638 use_local_qiov = true;
1639 }
1640
1641 tail_bytes = (offset + bytes) & (align - 1);
1642 qemu_iovec_add(&local_qiov, tail_buf + tail_bytes, align - tail_bytes);
1643
1644 bytes = ROUND_UP(bytes, align);
1645 }
1646
1647 ret = bdrv_aligned_pwritev(child, &req, offset, bytes, align,
1648 use_local_qiov ? &local_qiov : qiov,
1649 flags);
1650
1651 fail:
1652
1653 if (use_local_qiov) {
1654 qemu_iovec_destroy(&local_qiov);
1655 }
1656 qemu_vfree(head_buf);
1657 qemu_vfree(tail_buf);
1658 out:
1659 tracked_request_end(&req);
1660 bdrv_dec_in_flight(bs);
1661 return ret;
1662 }
1663
1664 static int coroutine_fn bdrv_co_do_writev(BdrvChild *child,
1665 int64_t sector_num, int nb_sectors, QEMUIOVector *qiov,
1666 BdrvRequestFlags flags)
1667 {
1668 if (nb_sectors < 0 || nb_sectors > BDRV_REQUEST_MAX_SECTORS) {
1669 return -EINVAL;
1670 }
1671
1672 return bdrv_co_pwritev(child, sector_num << BDRV_SECTOR_BITS,
1673 nb_sectors << BDRV_SECTOR_BITS, qiov, flags);
1674 }
1675
1676 int coroutine_fn bdrv_co_writev(BdrvChild *child, int64_t sector_num,
1677 int nb_sectors, QEMUIOVector *qiov)
1678 {
1679 trace_bdrv_co_writev(child->bs, sector_num, nb_sectors);
1680
1681 return bdrv_co_do_writev(child, sector_num, nb_sectors, qiov, 0);
1682 }
1683
1684 int coroutine_fn bdrv_co_pwrite_zeroes(BdrvChild *child, int64_t offset,
1685 int count, BdrvRequestFlags flags)
1686 {
1687 trace_bdrv_co_pwrite_zeroes(child->bs, offset, count, flags);
1688
1689 if (!(child->bs->open_flags & BDRV_O_UNMAP)) {
1690 flags &= ~BDRV_REQ_MAY_UNMAP;
1691 }
1692
1693 return bdrv_co_pwritev(child, offset, count, NULL,
1694 BDRV_REQ_ZERO_WRITE | flags);
1695 }
1696
1697 /*
1698 * Flush ALL BDSes regardless of if they are reachable via a BlkBackend or not.
1699 */
1700 int bdrv_flush_all(void)
1701 {
1702 BdrvNextIterator it;
1703 BlockDriverState *bs = NULL;
1704 int result = 0;
1705
1706 for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
1707 AioContext *aio_context = bdrv_get_aio_context(bs);
1708 int ret;
1709
1710 aio_context_acquire(aio_context);
1711 ret = bdrv_flush(bs);
1712 if (ret < 0 && !result) {
1713 result = ret;
1714 }
1715 aio_context_release(aio_context);
1716 }
1717
1718 return result;
1719 }
1720
1721
1722 typedef struct BdrvCoGetBlockStatusData {
1723 BlockDriverState *bs;
1724 BlockDriverState *base;
1725 BlockDriverState **file;
1726 int64_t sector_num;
1727 int nb_sectors;
1728 int *pnum;
1729 int64_t ret;
1730 bool done;
1731 } BdrvCoGetBlockStatusData;
1732
1733 /*
1734 * Returns the allocation status of the specified sectors.
1735 * Drivers not implementing the functionality are assumed to not support
1736 * backing files, hence all their sectors are reported as allocated.
1737 *
1738 * If 'sector_num' is beyond the end of the disk image the return value is 0
1739 * and 'pnum' is set to 0.
1740 *
1741 * 'pnum' is set to the number of sectors (including and immediately following
1742 * the specified sector) that are known to be in the same
1743 * allocated/unallocated state.
1744 *
1745 * 'nb_sectors' is the max value 'pnum' should be set to. If nb_sectors goes
1746 * beyond the end of the disk image it will be clamped.
1747 *
1748 * If returned value is positive and BDRV_BLOCK_OFFSET_VALID bit is set, 'file'
1749 * points to the BDS which the sector range is allocated in.
1750 */
1751 static int64_t coroutine_fn bdrv_co_get_block_status(BlockDriverState *bs,
1752 int64_t sector_num,
1753 int nb_sectors, int *pnum,
1754 BlockDriverState **file)
1755 {
1756 int64_t total_sectors;
1757 int64_t n;
1758 int64_t ret, ret2;
1759
1760 total_sectors = bdrv_nb_sectors(bs);
1761 if (total_sectors < 0) {
1762 return total_sectors;
1763 }
1764
1765 if (sector_num >= total_sectors) {
1766 *pnum = 0;
1767 return 0;
1768 }
1769
1770 n = total_sectors - sector_num;
1771 if (n < nb_sectors) {
1772 nb_sectors = n;
1773 }
1774
1775 if (!bs->drv->bdrv_co_get_block_status) {
1776 *pnum = nb_sectors;
1777 ret = BDRV_BLOCK_DATA | BDRV_BLOCK_ALLOCATED;
1778 if (bs->drv->protocol_name) {
1779 ret |= BDRV_BLOCK_OFFSET_VALID | (sector_num * BDRV_SECTOR_SIZE);
1780 }
1781 return ret;
1782 }
1783
1784 *file = NULL;
1785 bdrv_inc_in_flight(bs);
1786 ret = bs->drv->bdrv_co_get_block_status(bs, sector_num, nb_sectors, pnum,
1787 file);
1788 if (ret < 0) {
1789 *pnum = 0;
1790 goto out;
1791 }
1792
1793 if (ret & BDRV_BLOCK_RAW) {
1794 assert(ret & BDRV_BLOCK_OFFSET_VALID);
1795 ret = bdrv_get_block_status(*file, ret >> BDRV_SECTOR_BITS,
1796 *pnum, pnum, file);
1797 goto out;
1798 }
1799
1800 if (ret & (BDRV_BLOCK_DATA | BDRV_BLOCK_ZERO)) {
1801 ret |= BDRV_BLOCK_ALLOCATED;
1802 } else {
1803 if (bdrv_unallocated_blocks_are_zero(bs)) {
1804 ret |= BDRV_BLOCK_ZERO;
1805 } else if (bs->backing) {
1806 BlockDriverState *bs2 = bs->backing->bs;
1807 int64_t nb_sectors2 = bdrv_nb_sectors(bs2);
1808 if (nb_sectors2 >= 0 && sector_num >= nb_sectors2) {
1809 ret |= BDRV_BLOCK_ZERO;
1810 }
1811 }
1812 }
1813
1814 if (*file && *file != bs &&
1815 (ret & BDRV_BLOCK_DATA) && !(ret & BDRV_BLOCK_ZERO) &&
1816 (ret & BDRV_BLOCK_OFFSET_VALID)) {
1817 BlockDriverState *file2;
1818 int file_pnum;
1819
1820 ret2 = bdrv_co_get_block_status(*file, ret >> BDRV_SECTOR_BITS,
1821 *pnum, &file_pnum, &file2);
1822 if (ret2 >= 0) {
1823 /* Ignore errors. This is just providing extra information, it
1824 * is useful but not necessary.
1825 */
1826 if (!file_pnum) {
1827 /* !file_pnum indicates an offset at or beyond the EOF; it is
1828 * perfectly valid for the format block driver to point to such
1829 * offsets, so catch it and mark everything as zero */
1830 ret |= BDRV_BLOCK_ZERO;
1831 } else {
1832 /* Limit request to the range reported by the protocol driver */
1833 *pnum = file_pnum;
1834 ret |= (ret2 & BDRV_BLOCK_ZERO);
1835 }
1836 }
1837 }
1838
1839 out:
1840 bdrv_dec_in_flight(bs);
1841 return ret;
1842 }
1843
1844 static int64_t coroutine_fn bdrv_co_get_block_status_above(BlockDriverState *bs,
1845 BlockDriverState *base,
1846 int64_t sector_num,
1847 int nb_sectors,
1848 int *pnum,
1849 BlockDriverState **file)
1850 {
1851 BlockDriverState *p;
1852 int64_t ret = 0;
1853
1854 assert(bs != base);
1855 for (p = bs; p != base; p = backing_bs(p)) {
1856 ret = bdrv_co_get_block_status(p, sector_num, nb_sectors, pnum, file);
1857 if (ret < 0 || ret & BDRV_BLOCK_ALLOCATED) {
1858 break;
1859 }
1860 /* [sector_num, pnum] unallocated on this layer, which could be only
1861 * the first part of [sector_num, nb_sectors]. */
1862 nb_sectors = MIN(nb_sectors, *pnum);
1863 }
1864 return ret;
1865 }
1866
1867 /* Coroutine wrapper for bdrv_get_block_status_above() */
1868 static void coroutine_fn bdrv_get_block_status_above_co_entry(void *opaque)
1869 {
1870 BdrvCoGetBlockStatusData *data = opaque;
1871
1872 data->ret = bdrv_co_get_block_status_above(data->bs, data->base,
1873 data->sector_num,
1874 data->nb_sectors,
1875 data->pnum,
1876 data->file);
1877 data->done = true;
1878 }
1879
1880 /*
1881 * Synchronous wrapper around bdrv_co_get_block_status_above().
1882 *
1883 * See bdrv_co_get_block_status_above() for details.
1884 */
1885 int64_t bdrv_get_block_status_above(BlockDriverState *bs,
1886 BlockDriverState *base,
1887 int64_t sector_num,
1888 int nb_sectors, int *pnum,
1889 BlockDriverState **file)
1890 {
1891 Coroutine *co;
1892 BdrvCoGetBlockStatusData data = {
1893 .bs = bs,
1894 .base = base,
1895 .file = file,
1896 .sector_num = sector_num,
1897 .nb_sectors = nb_sectors,
1898 .pnum = pnum,
1899 .done = false,
1900 };
1901
1902 if (qemu_in_coroutine()) {
1903 /* Fast-path if already in coroutine context */
1904 bdrv_get_block_status_above_co_entry(&data);
1905 } else {
1906 co = qemu_coroutine_create(bdrv_get_block_status_above_co_entry,
1907 &data);
1908 bdrv_coroutine_enter(bs, co);
1909 BDRV_POLL_WHILE(bs, !data.done);
1910 }
1911 return data.ret;
1912 }
1913
1914 int64_t bdrv_get_block_status(BlockDriverState *bs,
1915 int64_t sector_num,
1916 int nb_sectors, int *pnum,
1917 BlockDriverState **file)
1918 {
1919 return bdrv_get_block_status_above(bs, backing_bs(bs),
1920 sector_num, nb_sectors, pnum, file);
1921 }
1922
1923 int coroutine_fn bdrv_is_allocated(BlockDriverState *bs, int64_t sector_num,
1924 int nb_sectors, int *pnum)
1925 {
1926 BlockDriverState *file;
1927 int64_t ret = bdrv_get_block_status(bs, sector_num, nb_sectors, pnum,
1928 &file);
1929 if (ret < 0) {
1930 return ret;
1931 }
1932 return !!(ret & BDRV_BLOCK_ALLOCATED);
1933 }
1934
1935 /*
1936 * Given an image chain: ... -> [BASE] -> [INTER1] -> [INTER2] -> [TOP]
1937 *
1938 * Return true if the given sector is allocated in any image between
1939 * BASE and TOP (inclusive). BASE can be NULL to check if the given
1940 * sector is allocated in any image of the chain. Return false otherwise.
1941 *
1942 * 'pnum' is set to the number of sectors (including and immediately following
1943 * the specified sector) that are known to be in the same
1944 * allocated/unallocated state.
1945 *
1946 */
1947 int bdrv_is_allocated_above(BlockDriverState *top,
1948 BlockDriverState *base,
1949 int64_t sector_num,
1950 int nb_sectors, int *pnum)
1951 {
1952 BlockDriverState *intermediate;
1953 int ret, n = nb_sectors;
1954
1955 intermediate = top;
1956 while (intermediate && intermediate != base) {
1957 int pnum_inter;
1958 ret = bdrv_is_allocated(intermediate, sector_num, nb_sectors,
1959 &pnum_inter);
1960 if (ret < 0) {
1961 return ret;
1962 } else if (ret) {
1963 *pnum = pnum_inter;
1964 return 1;
1965 }
1966
1967 /*
1968 * [sector_num, nb_sectors] is unallocated on top but intermediate
1969 * might have
1970 *
1971 * [sector_num+x, nr_sectors] allocated.
1972 */
1973 if (n > pnum_inter &&
1974 (intermediate == top ||
1975 sector_num + pnum_inter < intermediate->total_sectors)) {
1976 n = pnum_inter;
1977 }
1978
1979 intermediate = backing_bs(intermediate);
1980 }
1981
1982 *pnum = n;
1983 return 0;
1984 }
1985
1986 typedef struct BdrvVmstateCo {
1987 BlockDriverState *bs;
1988 QEMUIOVector *qiov;
1989 int64_t pos;
1990 bool is_read;
1991 int ret;
1992 } BdrvVmstateCo;
1993
1994 static int coroutine_fn
1995 bdrv_co_rw_vmstate(BlockDriverState *bs, QEMUIOVector *qiov, int64_t pos,
1996 bool is_read)
1997 {
1998 BlockDriver *drv = bs->drv;
1999
2000 if (!drv) {
2001 return -ENOMEDIUM;
2002 } else if (drv->bdrv_load_vmstate) {
2003 return is_read ? drv->bdrv_load_vmstate(bs, qiov, pos)
2004 : drv->bdrv_save_vmstate(bs, qiov, pos);
2005 } else if (bs->file) {
2006 return bdrv_co_rw_vmstate(bs->file->bs, qiov, pos, is_read);
2007 }
2008
2009 return -ENOTSUP;
2010 }
2011
2012 static void coroutine_fn bdrv_co_rw_vmstate_entry(void *opaque)
2013 {
2014 BdrvVmstateCo *co = opaque;
2015 co->ret = bdrv_co_rw_vmstate(co->bs, co->qiov, co->pos, co->is_read);
2016 }
2017
2018 static inline int
2019 bdrv_rw_vmstate(BlockDriverState *bs, QEMUIOVector *qiov, int64_t pos,
2020 bool is_read)
2021 {
2022 if (qemu_in_coroutine()) {
2023 return bdrv_co_rw_vmstate(bs, qiov, pos, is_read);
2024 } else {
2025 BdrvVmstateCo data = {
2026 .bs = bs,
2027 .qiov = qiov,
2028 .pos = pos,
2029 .is_read = is_read,
2030 .ret = -EINPROGRESS,
2031 };
2032 Coroutine *co = qemu_coroutine_create(bdrv_co_rw_vmstate_entry, &data);
2033
2034 bdrv_coroutine_enter(bs, co);
2035 while (data.ret == -EINPROGRESS) {
2036 aio_poll(bdrv_get_aio_context(bs), true);
2037 }
2038 return data.ret;
2039 }
2040 }
2041
2042 int bdrv_save_vmstate(BlockDriverState *bs, const uint8_t *buf,
2043 int64_t pos, int size)
2044 {
2045 QEMUIOVector qiov;
2046 struct iovec iov = {
2047 .iov_base = (void *) buf,
2048 .iov_len = size,
2049 };
2050 int ret;
2051
2052 qemu_iovec_init_external(&qiov, &iov, 1);
2053
2054 ret = bdrv_writev_vmstate(bs, &qiov, pos);
2055 if (ret < 0) {
2056 return ret;
2057 }
2058
2059 return size;
2060 }
2061
2062 int bdrv_writev_vmstate(BlockDriverState *bs, QEMUIOVector *qiov, int64_t pos)
2063 {
2064 return bdrv_rw_vmstate(bs, qiov, pos, false);
2065 }
2066
2067 int bdrv_load_vmstate(BlockDriverState *bs, uint8_t *buf,
2068 int64_t pos, int size)
2069 {
2070 QEMUIOVector qiov;
2071 struct iovec iov = {
2072 .iov_base = buf,
2073 .iov_len = size,
2074 };
2075 int ret;
2076
2077 qemu_iovec_init_external(&qiov, &iov, 1);
2078 ret = bdrv_readv_vmstate(bs, &qiov, pos);
2079 if (ret < 0) {
2080 return ret;
2081 }
2082
2083 return size;
2084 }
2085
2086 int bdrv_readv_vmstate(BlockDriverState *bs, QEMUIOVector *qiov, int64_t pos)
2087 {
2088 return bdrv_rw_vmstate(bs, qiov, pos, true);
2089 }
2090
2091 /**************************************************************/
2092 /* async I/Os */
2093
2094 BlockAIOCB *bdrv_aio_readv(BdrvChild *child, int64_t sector_num,
2095 QEMUIOVector *qiov, int nb_sectors,
2096 BlockCompletionFunc *cb, void *opaque)
2097 {
2098 trace_bdrv_aio_readv(child->bs, sector_num, nb_sectors, opaque);
2099
2100 assert(nb_sectors << BDRV_SECTOR_BITS == qiov->size);
2101 return bdrv_co_aio_prw_vector(child, sector_num << BDRV_SECTOR_BITS, qiov,
2102 0, cb, opaque, false);
2103 }
2104
2105 BlockAIOCB *bdrv_aio_writev(BdrvChild *child, int64_t sector_num,
2106 QEMUIOVector *qiov, int nb_sectors,
2107 BlockCompletionFunc *cb, void *opaque)
2108 {
2109 trace_bdrv_aio_writev(child->bs, sector_num, nb_sectors, opaque);
2110
2111 assert(nb_sectors << BDRV_SECTOR_BITS == qiov->size);
2112 return bdrv_co_aio_prw_vector(child, sector_num << BDRV_SECTOR_BITS, qiov,
2113 0, cb, opaque, true);
2114 }
2115
2116 void bdrv_aio_cancel(BlockAIOCB *acb)
2117 {
2118 qemu_aio_ref(acb);
2119 bdrv_aio_cancel_async(acb);
2120 while (acb->refcnt > 1) {
2121 if (acb->aiocb_info->get_aio_context) {
2122 aio_poll(acb->aiocb_info->get_aio_context(acb), true);
2123 } else if (acb->bs) {
2124 /* qemu_aio_ref and qemu_aio_unref are not thread-safe, so
2125 * assert that we're not using an I/O thread. Thread-safe
2126 * code should use bdrv_aio_cancel_async exclusively.
2127 */
2128 assert(bdrv_get_aio_context(acb->bs) == qemu_get_aio_context());
2129 aio_poll(bdrv_get_aio_context(acb->bs), true);
2130 } else {
2131 abort();
2132 }
2133 }
2134 qemu_aio_unref(acb);
2135 }
2136
2137 /* Async version of aio cancel. The caller is not blocked if the acb implements
2138 * cancel_async, otherwise we do nothing and let the request normally complete.
2139 * In either case the completion callback must be called. */
2140 void bdrv_aio_cancel_async(BlockAIOCB *acb)
2141 {
2142 if (acb->aiocb_info->cancel_async) {
2143 acb->aiocb_info->cancel_async(acb);
2144 }
2145 }
2146
2147 /**************************************************************/
2148 /* async block device emulation */
2149
2150 typedef struct BlockRequest {
2151 union {
2152 /* Used during read, write, trim */
2153 struct {
2154 int64_t offset;
2155 int bytes;
2156 int flags;
2157 QEMUIOVector *qiov;
2158 };
2159 /* Used during ioctl */
2160 struct {
2161 int req;
2162 void *buf;
2163 };
2164 };
2165 BlockCompletionFunc *cb;
2166 void *opaque;
2167
2168 int error;
2169 } BlockRequest;
2170
2171 typedef struct BlockAIOCBCoroutine {
2172 BlockAIOCB common;
2173 BdrvChild *child;
2174 BlockRequest req;
2175 bool is_write;
2176 bool need_bh;
2177 bool *done;
2178 } BlockAIOCBCoroutine;
2179
2180 static const AIOCBInfo bdrv_em_co_aiocb_info = {
2181 .aiocb_size = sizeof(BlockAIOCBCoroutine),
2182 };
2183
2184 static void bdrv_co_complete(BlockAIOCBCoroutine *acb)
2185 {
2186 if (!acb->need_bh) {
2187 bdrv_dec_in_flight(acb->common.bs);
2188 acb->common.cb(acb->common.opaque, acb->req.error);
2189 qemu_aio_unref(acb);
2190 }
2191 }
2192
2193 static void bdrv_co_em_bh(void *opaque)
2194 {
2195 BlockAIOCBCoroutine *acb = opaque;
2196
2197 assert(!acb->need_bh);
2198 bdrv_co_complete(acb);
2199 }
2200
2201 static void bdrv_co_maybe_schedule_bh(BlockAIOCBCoroutine *acb)
2202 {
2203 acb->need_bh = false;
2204 if (acb->req.error != -EINPROGRESS) {
2205 BlockDriverState *bs = acb->common.bs;
2206
2207 aio_bh_schedule_oneshot(bdrv_get_aio_context(bs), bdrv_co_em_bh, acb);
2208 }
2209 }
2210
2211 /* Invoke bdrv_co_do_readv/bdrv_co_do_writev */
2212 static void coroutine_fn bdrv_co_do_rw(void *opaque)
2213 {
2214 BlockAIOCBCoroutine *acb = opaque;
2215
2216 if (!acb->is_write) {
2217 acb->req.error = bdrv_co_preadv(acb->child, acb->req.offset,
2218 acb->req.qiov->size, acb->req.qiov, acb->req.flags);
2219 } else {
2220 acb->req.error = bdrv_co_pwritev(acb->child, acb->req.offset,
2221 acb->req.qiov->size, acb->req.qiov, acb->req.flags);
2222 }
2223
2224 bdrv_co_complete(acb);
2225 }
2226
2227 static BlockAIOCB *bdrv_co_aio_prw_vector(BdrvChild *child,
2228 int64_t offset,
2229 QEMUIOVector *qiov,
2230 BdrvRequestFlags flags,
2231 BlockCompletionFunc *cb,
2232 void *opaque,
2233 bool is_write)
2234 {
2235 Coroutine *co;
2236 BlockAIOCBCoroutine *acb;
2237
2238 /* Matched by bdrv_co_complete's bdrv_dec_in_flight. */
2239 bdrv_inc_in_flight(child->bs);
2240
2241 acb = qemu_aio_get(&bdrv_em_co_aiocb_info, child->bs, cb, opaque);
2242 acb->child = child;
2243 acb->need_bh = true;
2244 acb->req.error = -EINPROGRESS;
2245 acb->req.offset = offset;
2246 acb->req.qiov = qiov;
2247 acb->req.flags = flags;
2248 acb->is_write = is_write;
2249
2250 co = qemu_coroutine_create(bdrv_co_do_rw, acb);
2251 bdrv_coroutine_enter(child->bs, co);
2252
2253 bdrv_co_maybe_schedule_bh(acb);
2254 return &acb->common;
2255 }
2256
2257 static void coroutine_fn bdrv_aio_flush_co_entry(void *opaque)
2258 {
2259 BlockAIOCBCoroutine *acb = opaque;
2260 BlockDriverState *bs = acb->common.bs;
2261
2262 acb->req.error = bdrv_co_flush(bs);
2263 bdrv_co_complete(acb);
2264 }
2265
2266 BlockAIOCB *bdrv_aio_flush(BlockDriverState *bs,
2267 BlockCompletionFunc *cb, void *opaque)
2268 {
2269 trace_bdrv_aio_flush(bs, opaque);
2270
2271 Coroutine *co;
2272 BlockAIOCBCoroutine *acb;
2273
2274 /* Matched by bdrv_co_complete's bdrv_dec_in_flight. */
2275 bdrv_inc_in_flight(bs);
2276
2277 acb = qemu_aio_get(&bdrv_em_co_aiocb_info, bs, cb, opaque);
2278 acb->need_bh = true;
2279 acb->req.error = -EINPROGRESS;
2280
2281 co = qemu_coroutine_create(bdrv_aio_flush_co_entry, acb);
2282 bdrv_coroutine_enter(bs, co);
2283
2284 bdrv_co_maybe_schedule_bh(acb);
2285 return &acb->common;
2286 }
2287
2288 /**************************************************************/
2289 /* Coroutine block device emulation */
2290
2291 typedef struct FlushCo {
2292 BlockDriverState *bs;
2293 int ret;
2294 } FlushCo;
2295
2296
2297 static void coroutine_fn bdrv_flush_co_entry(void *opaque)
2298 {
2299 FlushCo *rwco = opaque;
2300
2301 rwco->ret = bdrv_co_flush(rwco->bs);
2302 }
2303
2304 int coroutine_fn bdrv_co_flush(BlockDriverState *bs)
2305 {
2306 int current_gen;
2307 int ret = 0;
2308
2309 bdrv_inc_in_flight(bs);
2310
2311 if (!bs || !bdrv_is_inserted(bs) || bdrv_is_read_only(bs) ||
2312 bdrv_is_sg(bs)) {
2313 goto early_exit;
2314 }
2315
2316 current_gen = bs->write_gen;
2317
2318 /* Wait until any previous flushes are completed */
2319 while (bs->active_flush_req) {
2320 qemu_co_queue_wait(&bs->flush_queue, NULL);
2321 }
2322
2323 bs->active_flush_req = true;
2324
2325 /* Write back all layers by calling one driver function */
2326 if (bs->drv->bdrv_co_flush) {
2327 ret = bs->drv->bdrv_co_flush(bs);
2328 goto out;
2329 }
2330
2331 /* Write back cached data to the OS even with cache=unsafe */
2332 BLKDBG_EVENT(bs->file, BLKDBG_FLUSH_TO_OS);
2333 if (bs->drv->bdrv_co_flush_to_os) {
2334 ret = bs->drv->bdrv_co_flush_to_os(bs);
2335 if (ret < 0) {
2336 goto out;
2337 }
2338 }
2339
2340 /* But don't actually force it to the disk with cache=unsafe */
2341 if (bs->open_flags & BDRV_O_NO_FLUSH) {
2342 goto flush_parent;
2343 }
2344
2345 /* Check if we really need to flush anything */
2346 if (bs->flushed_gen == current_gen) {
2347 goto flush_parent;
2348 }
2349
2350 BLKDBG_EVENT(bs->file, BLKDBG_FLUSH_TO_DISK);
2351 if (bs->drv->bdrv_co_flush_to_disk) {
2352 ret = bs->drv->bdrv_co_flush_to_disk(bs);
2353 } else if (bs->drv->bdrv_aio_flush) {
2354 BlockAIOCB *acb;
2355 CoroutineIOCompletion co = {
2356 .coroutine = qemu_coroutine_self(),
2357 };
2358
2359 acb = bs->drv->bdrv_aio_flush(bs, bdrv_co_io_em_complete, &co);
2360 if (acb == NULL) {
2361 ret = -EIO;
2362 } else {
2363 qemu_coroutine_yield();
2364 ret = co.ret;
2365 }
2366 } else {
2367 /*
2368 * Some block drivers always operate in either writethrough or unsafe
2369 * mode and don't support bdrv_flush therefore. Usually qemu doesn't
2370 * know how the server works (because the behaviour is hardcoded or
2371 * depends on server-side configuration), so we can't ensure that
2372 * everything is safe on disk. Returning an error doesn't work because
2373 * that would break guests even if the server operates in writethrough
2374 * mode.
2375 *
2376 * Let's hope the user knows what he's doing.
2377 */
2378 ret = 0;
2379 }
2380
2381 if (ret < 0) {
2382 goto out;
2383 }
2384
2385 /* Now flush the underlying protocol. It will also have BDRV_O_NO_FLUSH
2386 * in the case of cache=unsafe, so there are no useless flushes.
2387 */
2388 flush_parent:
2389 ret = bs->file ? bdrv_co_flush(bs->file->bs) : 0;
2390 out:
2391 /* Notify any pending flushes that we have completed */
2392 if (ret == 0) {
2393 bs->flushed_gen = current_gen;
2394 }
2395 bs->active_flush_req = false;
2396 /* Return value is ignored - it's ok if wait queue is empty */
2397 qemu_co_queue_next(&bs->flush_queue);
2398
2399 early_exit:
2400 bdrv_dec_in_flight(bs);
2401 return ret;
2402 }
2403
2404 int bdrv_flush(BlockDriverState *bs)
2405 {
2406 Coroutine *co;
2407 FlushCo flush_co = {
2408 .bs = bs,
2409 .ret = NOT_DONE,
2410 };
2411
2412 if (qemu_in_coroutine()) {
2413 /* Fast-path if already in coroutine context */
2414 bdrv_flush_co_entry(&flush_co);
2415 } else {
2416 co = qemu_coroutine_create(bdrv_flush_co_entry, &flush_co);
2417 bdrv_coroutine_enter(bs, co);
2418 BDRV_POLL_WHILE(bs, flush_co.ret == NOT_DONE);
2419 }
2420
2421 return flush_co.ret;
2422 }
2423
2424 typedef struct DiscardCo {
2425 BlockDriverState *bs;
2426 int64_t offset;
2427 int count;
2428 int ret;
2429 } DiscardCo;
2430 static void coroutine_fn bdrv_pdiscard_co_entry(void *opaque)
2431 {
2432 DiscardCo *rwco = opaque;
2433
2434 rwco->ret = bdrv_co_pdiscard(rwco->bs, rwco->offset, rwco->count);
2435 }
2436
2437 int coroutine_fn bdrv_co_pdiscard(BlockDriverState *bs, int64_t offset,
2438 int count)
2439 {
2440 BdrvTrackedRequest req;
2441 int max_pdiscard, ret;
2442 int head, tail, align;
2443
2444 if (!bs->drv) {
2445 return -ENOMEDIUM;
2446 }
2447
2448 ret = bdrv_check_byte_request(bs, offset, count);
2449 if (ret < 0) {
2450 return ret;
2451 } else if (bs->read_only) {
2452 return -EPERM;
2453 }
2454 assert(!(bs->open_flags & BDRV_O_INACTIVE));
2455
2456 /* Do nothing if disabled. */
2457 if (!(bs->open_flags & BDRV_O_UNMAP)) {
2458 return 0;
2459 }
2460
2461 if (!bs->drv->bdrv_co_pdiscard && !bs->drv->bdrv_aio_pdiscard) {
2462 return 0;
2463 }
2464
2465 /* Discard is advisory, but some devices track and coalesce
2466 * unaligned requests, so we must pass everything down rather than
2467 * round here. Still, most devices will just silently ignore
2468 * unaligned requests (by returning -ENOTSUP), so we must fragment
2469 * the request accordingly. */
2470 align = MAX(bs->bl.pdiscard_alignment, bs->bl.request_alignment);
2471 assert(align % bs->bl.request_alignment == 0);
2472 head = offset % align;
2473 tail = (offset + count) % align;
2474
2475 bdrv_inc_in_flight(bs);
2476 tracked_request_begin(&req, bs, offset, count, BDRV_TRACKED_DISCARD);
2477
2478 ret = notifier_with_return_list_notify(&bs->before_write_notifiers, &req);
2479 if (ret < 0) {
2480 goto out;
2481 }
2482
2483 max_pdiscard = QEMU_ALIGN_DOWN(MIN_NON_ZERO(bs->bl.max_pdiscard, INT_MAX),
2484 align);
2485 assert(max_pdiscard >= bs->bl.request_alignment);
2486
2487 while (count > 0) {
2488 int ret;
2489 int num = count;
2490
2491 if (head) {
2492 /* Make small requests to get to alignment boundaries. */
2493 num = MIN(count, align - head);
2494 if (!QEMU_IS_ALIGNED(num, bs->bl.request_alignment)) {
2495 num %= bs->bl.request_alignment;
2496 }
2497 head = (head + num) % align;
2498 assert(num < max_pdiscard);
2499 } else if (tail) {
2500 if (num > align) {
2501 /* Shorten the request to the last aligned cluster. */
2502 num -= tail;
2503 } else if (!QEMU_IS_ALIGNED(tail, bs->bl.request_alignment) &&
2504 tail > bs->bl.request_alignment) {
2505 tail %= bs->bl.request_alignment;
2506 num -= tail;
2507 }
2508 }
2509 /* limit request size */
2510 if (num > max_pdiscard) {
2511 num = max_pdiscard;
2512 }
2513
2514 if (bs->drv->bdrv_co_pdiscard) {
2515 ret = bs->drv->bdrv_co_pdiscard(bs, offset, num);
2516 } else {
2517 BlockAIOCB *acb;
2518 CoroutineIOCompletion co = {
2519 .coroutine = qemu_coroutine_self(),
2520 };
2521
2522 acb = bs->drv->bdrv_aio_pdiscard(bs, offset, num,
2523 bdrv_co_io_em_complete, &co);
2524 if (acb == NULL) {
2525 ret = -EIO;
2526 goto out;
2527 } else {
2528 qemu_coroutine_yield();
2529 ret = co.ret;
2530 }
2531 }
2532 if (ret && ret != -ENOTSUP) {
2533 goto out;
2534 }
2535
2536 offset += num;
2537 count -= num;
2538 }
2539 ret = 0;
2540 out:
2541 ++bs->write_gen;
2542 bdrv_set_dirty(bs, req.offset >> BDRV_SECTOR_BITS,
2543 req.bytes >> BDRV_SECTOR_BITS);
2544 tracked_request_end(&req);
2545 bdrv_dec_in_flight(bs);
2546 return ret;
2547 }
2548
2549 int bdrv_pdiscard(BlockDriverState *bs, int64_t offset, int count)
2550 {
2551 Coroutine *co;
2552 DiscardCo rwco = {
2553 .bs = bs,
2554 .offset = offset,
2555 .count = count,
2556 .ret = NOT_DONE,
2557 };
2558
2559 if (qemu_in_coroutine()) {
2560 /* Fast-path if already in coroutine context */
2561 bdrv_pdiscard_co_entry(&rwco);
2562 } else {
2563 co = qemu_coroutine_create(bdrv_pdiscard_co_entry, &rwco);
2564 bdrv_coroutine_enter(bs, co);
2565 BDRV_POLL_WHILE(bs, rwco.ret == NOT_DONE);
2566 }
2567
2568 return rwco.ret;
2569 }
2570
2571 int bdrv_co_ioctl(BlockDriverState *bs, int req, void *buf)
2572 {
2573 BlockDriver *drv = bs->drv;
2574 CoroutineIOCompletion co = {
2575 .coroutine = qemu_coroutine_self(),
2576 };
2577 BlockAIOCB *acb;
2578
2579 bdrv_inc_in_flight(bs);
2580 if (!drv || (!drv->bdrv_aio_ioctl && !drv->bdrv_co_ioctl)) {
2581 co.ret = -ENOTSUP;
2582 goto out;
2583 }
2584
2585 if (drv->bdrv_co_ioctl) {
2586 co.ret = drv->bdrv_co_ioctl(bs, req, buf);
2587 } else {
2588 acb = drv->bdrv_aio_ioctl(bs, req, buf, bdrv_co_io_em_complete, &co);
2589 if (!acb) {
2590 co.ret = -ENOTSUP;
2591 goto out;
2592 }
2593 qemu_coroutine_yield();
2594 }
2595 out:
2596 bdrv_dec_in_flight(bs);
2597 return co.ret;
2598 }
2599
2600 void *qemu_blockalign(BlockDriverState *bs, size_t size)
2601 {
2602 return qemu_memalign(bdrv_opt_mem_align(bs), size);
2603 }
2604
2605 void *qemu_blockalign0(BlockDriverState *bs, size_t size)
2606 {
2607 return memset(qemu_blockalign(bs, size), 0, size);
2608 }
2609
2610 void *qemu_try_blockalign(BlockDriverState *bs, size_t size)
2611 {
2612 size_t align = bdrv_opt_mem_align(bs);
2613
2614 /* Ensure that NULL is never returned on success */
2615 assert(align > 0);
2616 if (size == 0) {
2617 size = align;
2618 }
2619
2620 return qemu_try_memalign(align, size);
2621 }
2622
2623 void *qemu_try_blockalign0(BlockDriverState *bs, size_t size)
2624 {
2625 void *mem = qemu_try_blockalign(bs, size);
2626
2627 if (mem) {
2628 memset(mem, 0, size);
2629 }
2630
2631 return mem;
2632 }
2633
2634 /*
2635 * Check if all memory in this vector is sector aligned.
2636 */
2637 bool bdrv_qiov_is_aligned(BlockDriverState *bs, QEMUIOVector *qiov)
2638 {
2639 int i;
2640 size_t alignment = bdrv_min_mem_align(bs);
2641
2642 for (i = 0; i < qiov->niov; i++) {
2643 if ((uintptr_t) qiov->iov[i].iov_base % alignment) {
2644 return false;
2645 }
2646 if (qiov->iov[i].iov_len % alignment) {
2647 return false;
2648 }
2649 }
2650
2651 return true;
2652 }
2653
2654 void bdrv_add_before_write_notifier(BlockDriverState *bs,
2655 NotifierWithReturn *notifier)
2656 {
2657 notifier_with_return_list_add(&bs->before_write_notifiers, notifier);
2658 }
2659
2660 void bdrv_io_plug(BlockDriverState *bs)
2661 {
2662 BdrvChild *child;
2663
2664 QLIST_FOREACH(child, &bs->children, next) {
2665 bdrv_io_plug(child->bs);
2666 }
2667
2668 if (bs->io_plugged++ == 0) {
2669 BlockDriver *drv = bs->drv;
2670 if (drv && drv->bdrv_io_plug) {
2671 drv->bdrv_io_plug(bs);
2672 }
2673 }
2674 }
2675
2676 void bdrv_io_unplug(BlockDriverState *bs)
2677 {
2678 BdrvChild *child;
2679
2680 assert(bs->io_plugged);
2681 if (--bs->io_plugged == 0) {
2682 BlockDriver *drv = bs->drv;
2683 if (drv && drv->bdrv_io_unplug) {
2684 drv->bdrv_io_unplug(bs);
2685 }
2686 }
2687
2688 QLIST_FOREACH(child, &bs->children, next) {
2689 bdrv_io_unplug(child->bs);
2690 }
2691 }