/* * Block layer I/O functions * * Copyright (c) 2003 Fabrice Bellard * * Permission is hereby granted, free of charge, to any person obtaining a copy * of this software and associated documentation files (the "Software"), to deal * in the Software without restriction, including without limitation the rights * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell * copies of the Software, and to permit persons to whom the Software is * furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice shall be included in * all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN * THE SOFTWARE. */ #include "qemu/osdep.h" #include "trace.h" #include "sysemu/block-backend.h" #include "block/blockjob.h" #include "block/block_int.h" #include "qemu/cutils.h" #include "qapi/error.h" #include "qemu/error-report.h" #define NOT_DONE 0x7fffffff /* used while emulated sync operation in progress */ static BlockAIOCB *bdrv_co_aio_prw_vector(BdrvChild *child, int64_t offset, QEMUIOVector *qiov, BdrvRequestFlags flags, BlockCompletionFunc *cb, void *opaque, bool is_write); static void coroutine_fn bdrv_co_do_rw(void *opaque); static int coroutine_fn bdrv_co_do_pwrite_zeroes(BlockDriverState *bs, int64_t offset, int count, BdrvRequestFlags flags); static void bdrv_parent_drained_begin(BlockDriverState *bs) { BdrvChild *c; QLIST_FOREACH(c, &bs->parents, next_parent) { if (c->role->drained_begin) { c->role->drained_begin(c); } } } static void bdrv_parent_drained_end(BlockDriverState *bs) { BdrvChild *c; QLIST_FOREACH(c, &bs->parents, next_parent) { if (c->role->drained_end) { c->role->drained_end(c); } } } static void bdrv_merge_limits(BlockLimits *dst, const BlockLimits *src) { dst->opt_transfer = MAX(dst->opt_transfer, src->opt_transfer); dst->max_transfer = MIN_NON_ZERO(dst->max_transfer, src->max_transfer); dst->opt_mem_alignment = MAX(dst->opt_mem_alignment, src->opt_mem_alignment); dst->min_mem_alignment = MAX(dst->min_mem_alignment, src->min_mem_alignment); dst->max_iov = MIN_NON_ZERO(dst->max_iov, src->max_iov); } void bdrv_refresh_limits(BlockDriverState *bs, Error **errp) { BlockDriver *drv = bs->drv; Error *local_err = NULL; memset(&bs->bl, 0, sizeof(bs->bl)); if (!drv) { return; } /* Default alignment based on whether driver has byte interface */ bs->bl.request_alignment = drv->bdrv_co_preadv ? 1 : 512; /* Take some limits from the children as a default */ if (bs->file) { bdrv_refresh_limits(bs->file->bs, &local_err); if (local_err) { error_propagate(errp, local_err); return; } bdrv_merge_limits(&bs->bl, &bs->file->bs->bl); } else { bs->bl.min_mem_alignment = 512; bs->bl.opt_mem_alignment = getpagesize(); /* Safe default since most protocols use readv()/writev()/etc */ bs->bl.max_iov = IOV_MAX; } if (bs->backing) { bdrv_refresh_limits(bs->backing->bs, &local_err); if (local_err) { error_propagate(errp, local_err); return; } bdrv_merge_limits(&bs->bl, &bs->backing->bs->bl); } /* Then let the driver override it */ if (drv->bdrv_refresh_limits) { drv->bdrv_refresh_limits(bs, errp); } } /** * The copy-on-read flag is actually a reference count so multiple users may * use the feature without worrying about clobbering its previous state. * Copy-on-read stays enabled until all users have called to disable it. */ void bdrv_enable_copy_on_read(BlockDriverState *bs) { bs->copy_on_read++; } void bdrv_disable_copy_on_read(BlockDriverState *bs) { assert(bs->copy_on_read > 0); bs->copy_on_read--; } /* Check if any requests are in-flight (including throttled requests) */ bool bdrv_requests_pending(BlockDriverState *bs) { BdrvChild *child; if (atomic_read(&bs->in_flight)) { return true; } QLIST_FOREACH(child, &bs->children, next) { if (bdrv_requests_pending(child->bs)) { return true; } } return false; } static bool bdrv_drain_recurse(BlockDriverState *bs) { BdrvChild *child; bool waited; waited = BDRV_POLL_WHILE(bs, atomic_read(&bs->in_flight) > 0); if (bs->drv && bs->drv->bdrv_drain) { bs->drv->bdrv_drain(bs); } QLIST_FOREACH(child, &bs->children, next) { waited |= bdrv_drain_recurse(child->bs); } return waited; } typedef struct { Coroutine *co; BlockDriverState *bs; bool done; } BdrvCoDrainData; static void bdrv_co_drain_bh_cb(void *opaque) { BdrvCoDrainData *data = opaque; Coroutine *co = data->co; BlockDriverState *bs = data->bs; bdrv_dec_in_flight(bs); bdrv_drained_begin(bs); data->done = true; aio_co_wake(co); } static void coroutine_fn bdrv_co_yield_to_drain(BlockDriverState *bs) { BdrvCoDrainData data; /* Calling bdrv_drain() from a BH ensures the current coroutine yields and * other coroutines run if they were queued from * qemu_co_queue_run_restart(). */ assert(qemu_in_coroutine()); data = (BdrvCoDrainData) { .co = qemu_coroutine_self(), .bs = bs, .done = false, }; bdrv_inc_in_flight(bs); aio_bh_schedule_oneshot(bdrv_get_aio_context(bs), bdrv_co_drain_bh_cb, &data); qemu_coroutine_yield(); /* If we are resumed from some other event (such as an aio completion or a * timer callback), it is a bug in the caller that should be fixed. */ assert(data.done); } void bdrv_drained_begin(BlockDriverState *bs) { if (qemu_in_coroutine()) { bdrv_co_yield_to_drain(bs); return; } if (!bs->quiesce_counter++) { aio_disable_external(bdrv_get_aio_context(bs)); bdrv_parent_drained_begin(bs); } bdrv_drain_recurse(bs); } void bdrv_drained_end(BlockDriverState *bs) { assert(bs->quiesce_counter > 0); if (--bs->quiesce_counter > 0) { return; } bdrv_parent_drained_end(bs); aio_enable_external(bdrv_get_aio_context(bs)); } /* * Wait for pending requests to complete on a single BlockDriverState subtree, * and suspend block driver's internal I/O until next request arrives. * * Note that unlike bdrv_drain_all(), the caller must hold the BlockDriverState * AioContext. * * Only this BlockDriverState's AioContext is run, so in-flight requests must * not depend on events in other AioContexts. In that case, use * bdrv_drain_all() instead. */ void coroutine_fn bdrv_co_drain(BlockDriverState *bs) { assert(qemu_in_coroutine()); bdrv_drained_begin(bs); bdrv_drained_end(bs); } void bdrv_drain(BlockDriverState *bs) { bdrv_drained_begin(bs); bdrv_drained_end(bs); } /* * Wait for pending requests to complete across all BlockDriverStates * * This function does not flush data to disk, use bdrv_flush_all() for that * after calling this function. * * This pauses all block jobs and disables external clients. It must * be paired with bdrv_drain_all_end(). * * NOTE: no new block jobs or BlockDriverStates can be created between * the bdrv_drain_all_begin() and bdrv_drain_all_end() calls. */ void bdrv_drain_all_begin(void) { /* Always run first iteration so any pending completion BHs run */ bool waited = true; BlockDriverState *bs; BdrvNextIterator it; BlockJob *job = NULL; GSList *aio_ctxs = NULL, *ctx; while ((job = block_job_next(job))) { AioContext *aio_context = blk_get_aio_context(job->blk); aio_context_acquire(aio_context); block_job_pause(job); aio_context_release(aio_context); } for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) { AioContext *aio_context = bdrv_get_aio_context(bs); aio_context_acquire(aio_context); bdrv_parent_drained_begin(bs); aio_disable_external(aio_context); aio_context_release(aio_context); if (!g_slist_find(aio_ctxs, aio_context)) { aio_ctxs = g_slist_prepend(aio_ctxs, aio_context); } } /* Note that completion of an asynchronous I/O operation can trigger any * number of other I/O operations on other devices---for example a * coroutine can submit an I/O request to another device in response to * request completion. Therefore we must keep looping until there was no * more activity rather than simply draining each device independently. */ while (waited) { waited = false; for (ctx = aio_ctxs; ctx != NULL; ctx = ctx->next) { AioContext *aio_context = ctx->data; aio_context_acquire(aio_context); for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) { if (aio_context == bdrv_get_aio_context(bs)) { waited |= bdrv_drain_recurse(bs); } } aio_context_release(aio_context); } } g_slist_free(aio_ctxs); } void bdrv_drain_all_end(void) { BlockDriverState *bs; BdrvNextIterator it; BlockJob *job = NULL; for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) { AioContext *aio_context = bdrv_get_aio_context(bs); aio_context_acquire(aio_context); aio_enable_external(aio_context); bdrv_parent_drained_end(bs); aio_context_release(aio_context); } while ((job = block_job_next(job))) { AioContext *aio_context = blk_get_aio_context(job->blk); aio_context_acquire(aio_context); block_job_resume(job); aio_context_release(aio_context); } } void bdrv_drain_all(void) { bdrv_drain_all_begin(); bdrv_drain_all_end(); } /** * Remove an active request from the tracked requests list * * This function should be called when a tracked request is completing. */ static void tracked_request_end(BdrvTrackedRequest *req) { if (req->serialising) { req->bs->serialising_in_flight--; } QLIST_REMOVE(req, list); qemu_co_queue_restart_all(&req->wait_queue); } /** * Add an active request to the tracked requests list */ static void tracked_request_begin(BdrvTrackedRequest *req, BlockDriverState *bs, int64_t offset, unsigned int bytes, enum BdrvTrackedRequestType type) { *req = (BdrvTrackedRequest){ .bs = bs, .offset = offset, .bytes = bytes, .type = type, .co = qemu_coroutine_self(), .serialising = false, .overlap_offset = offset, .overlap_bytes = bytes, }; qemu_co_queue_init(&req->wait_queue); QLIST_INSERT_HEAD(&bs->tracked_requests, req, list); } static void mark_request_serialising(BdrvTrackedRequest *req, uint64_t align) { int64_t overlap_offset = req->offset & ~(align - 1); unsigned int overlap_bytes = ROUND_UP(req->offset + req->bytes, align) - overlap_offset; if (!req->serialising) { req->bs->serialising_in_flight++; req->serialising = true; } req->overlap_offset = MIN(req->overlap_offset, overlap_offset); req->overlap_bytes = MAX(req->overlap_bytes, overlap_bytes); } /** * Round a region to cluster boundaries (sector-based) */ void bdrv_round_sectors_to_clusters(BlockDriverState *bs, int64_t sector_num, int nb_sectors, int64_t *cluster_sector_num, int *cluster_nb_sectors) { BlockDriverInfo bdi; if (bdrv_get_info(bs, &bdi) < 0 || bdi.cluster_size == 0) { *cluster_sector_num = sector_num; *cluster_nb_sectors = nb_sectors; } else { int64_t c = bdi.cluster_size / BDRV_SECTOR_SIZE; *cluster_sector_num = QEMU_ALIGN_DOWN(sector_num, c); *cluster_nb_sectors = QEMU_ALIGN_UP(sector_num - *cluster_sector_num + nb_sectors, c); } } /** * Round a region to cluster boundaries */ void bdrv_round_to_clusters(BlockDriverState *bs, int64_t offset, unsigned int bytes, int64_t *cluster_offset, unsigned int *cluster_bytes) { BlockDriverInfo bdi; if (bdrv_get_info(bs, &bdi) < 0 || bdi.cluster_size == 0) { *cluster_offset = offset; *cluster_bytes = bytes; } else { int64_t c = bdi.cluster_size; *cluster_offset = QEMU_ALIGN_DOWN(offset, c); *cluster_bytes = QEMU_ALIGN_UP(offset - *cluster_offset + bytes, c); } } static int bdrv_get_cluster_size(BlockDriverState *bs) { BlockDriverInfo bdi; int ret; ret = bdrv_get_info(bs, &bdi); if (ret < 0 || bdi.cluster_size == 0) { return bs->bl.request_alignment; } else { return bdi.cluster_size; } } static bool tracked_request_overlaps(BdrvTrackedRequest *req, int64_t offset, unsigned int bytes) { /* aaaa bbbb */ if (offset >= req->overlap_offset + req->overlap_bytes) { return false; } /* bbbb aaaa */ if (req->overlap_offset >= offset + bytes) { return false; } return true; } void bdrv_inc_in_flight(BlockDriverState *bs) { atomic_inc(&bs->in_flight); } static void dummy_bh_cb(void *opaque) { } void bdrv_wakeup(BlockDriverState *bs) { if (bs->wakeup) { aio_bh_schedule_oneshot(qemu_get_aio_context(), dummy_bh_cb, NULL); } } void bdrv_dec_in_flight(BlockDriverState *bs) { atomic_dec(&bs->in_flight); bdrv_wakeup(bs); } static bool coroutine_fn wait_serialising_requests(BdrvTrackedRequest *self) { BlockDriverState *bs = self->bs; BdrvTrackedRequest *req; bool retry; bool waited = false; if (!bs->serialising_in_flight) { return false; } do { retry = false; QLIST_FOREACH(req, &bs->tracked_requests, list) { if (req == self || (!req->serialising && !self->serialising)) { continue; } if (tracked_request_overlaps(req, self->overlap_offset, self->overlap_bytes)) { /* Hitting this means there was a reentrant request, for * example, a block driver issuing nested requests. This must * never happen since it means deadlock. */ assert(qemu_coroutine_self() != req->co); /* If the request is already (indirectly) waiting for us, or * will wait for us as soon as it wakes up, then just go on * (instead of producing a deadlock in the former case). */ if (!req->waiting_for) { self->waiting_for = req; qemu_co_queue_wait(&req->wait_queue); self->waiting_for = NULL; retry = true; waited = true; break; } } } } while (retry); return waited; } static int bdrv_check_byte_request(BlockDriverState *bs, int64_t offset, size_t size) { if (size > BDRV_REQUEST_MAX_SECTORS << BDRV_SECTOR_BITS) { return -EIO; } if (!bdrv_is_inserted(bs)) { return -ENOMEDIUM; } if (offset < 0) { return -EIO; } return 0; } typedef struct RwCo { BdrvChild *child; int64_t offset; QEMUIOVector *qiov; bool is_write; int ret; BdrvRequestFlags flags; } RwCo; static void coroutine_fn bdrv_rw_co_entry(void *opaque) { RwCo *rwco = opaque; if (!rwco->is_write) { rwco->ret = bdrv_co_preadv(rwco->child, rwco->offset, rwco->qiov->size, rwco->qiov, rwco->flags); } else { rwco->ret = bdrv_co_pwritev(rwco->child, rwco->offset, rwco->qiov->size, rwco->qiov, rwco->flags); } } /* * Process a vectored synchronous request using coroutines */ static int bdrv_prwv_co(BdrvChild *child, int64_t offset, QEMUIOVector *qiov, bool is_write, BdrvRequestFlags flags) { Coroutine *co; RwCo rwco = { .child = child, .offset = offset, .qiov = qiov, .is_write = is_write, .ret = NOT_DONE, .flags = flags, }; if (qemu_in_coroutine()) { /* Fast-path if already in coroutine context */ bdrv_rw_co_entry(&rwco); } else { co = qemu_coroutine_create(bdrv_rw_co_entry, &rwco); qemu_coroutine_enter(co); BDRV_POLL_WHILE(child->bs, rwco.ret == NOT_DONE); } return rwco.ret; } /* * Process a synchronous request using coroutines */ static int bdrv_rw_co(BdrvChild *child, int64_t sector_num, uint8_t *buf, int nb_sectors, bool is_write, BdrvRequestFlags flags) { QEMUIOVector qiov; struct iovec iov = { .iov_base = (void *)buf, .iov_len = nb_sectors * BDRV_SECTOR_SIZE, }; if (nb_sectors < 0 || nb_sectors > BDRV_REQUEST_MAX_SECTORS) { return -EINVAL; } qemu_iovec_init_external(&qiov, &iov, 1); return bdrv_prwv_co(child, sector_num << BDRV_SECTOR_BITS, &qiov, is_write, flags); } /* return < 0 if error. See bdrv_write() for the return codes */ int bdrv_read(BdrvChild *child, int64_t sector_num, uint8_t *buf, int nb_sectors) { return bdrv_rw_co(child, sector_num, buf, nb_sectors, false, 0); } /* Return < 0 if error. Important errors are: -EIO generic I/O error (may happen for all errors) -ENOMEDIUM No media inserted. -EINVAL Invalid sector number or nb_sectors -EACCES Trying to write a read-only device */ int bdrv_write(BdrvChild *child, int64_t sector_num, const uint8_t *buf, int nb_sectors) { return bdrv_rw_co(child, sector_num, (uint8_t *)buf, nb_sectors, true, 0); } int bdrv_pwrite_zeroes(BdrvChild *child, int64_t offset, int count, BdrvRequestFlags flags) { QEMUIOVector qiov; struct iovec iov = { .iov_base = NULL, .iov_len = count, }; qemu_iovec_init_external(&qiov, &iov, 1); return bdrv_prwv_co(child, offset, &qiov, true, BDRV_REQ_ZERO_WRITE | flags); } /* * Completely zero out a block device with the help of bdrv_pwrite_zeroes. * The operation is sped up by checking the block status and only writing * zeroes to the device if they currently do not return zeroes. Optional * flags are passed through to bdrv_pwrite_zeroes (e.g. BDRV_REQ_MAY_UNMAP, * BDRV_REQ_FUA). * * Returns < 0 on error, 0 on success. For error codes see bdrv_write(). */ int bdrv_make_zero(BdrvChild *child, BdrvRequestFlags flags) { int64_t target_sectors, ret, nb_sectors, sector_num = 0; BlockDriverState *bs = child->bs; BlockDriverState *file; int n; target_sectors = bdrv_nb_sectors(bs); if (target_sectors < 0) { return target_sectors; } for (;;) { nb_sectors = MIN(target_sectors - sector_num, BDRV_REQUEST_MAX_SECTORS); if (nb_sectors <= 0) { return 0; } ret = bdrv_get_block_status(bs, sector_num, nb_sectors, &n, &file); if (ret < 0) { error_report("error getting block status at sector %" PRId64 ": %s", sector_num, strerror(-ret)); return ret; } if (ret & BDRV_BLOCK_ZERO) { sector_num += n; continue; } ret = bdrv_pwrite_zeroes(child, sector_num << BDRV_SECTOR_BITS, n << BDRV_SECTOR_BITS, flags); if (ret < 0) { error_report("error writing zeroes at sector %" PRId64 ": %s", sector_num, strerror(-ret)); return ret; } sector_num += n; } } int bdrv_preadv(BdrvChild *child, int64_t offset, QEMUIOVector *qiov) { int ret; ret = bdrv_prwv_co(child, offset, qiov, false, 0); if (ret < 0) { return ret; } return qiov->size; } int bdrv_pread(BdrvChild *child, int64_t offset, void *buf, int bytes) { QEMUIOVector qiov; struct iovec iov = { .iov_base = (void *)buf, .iov_len = bytes, }; if (bytes < 0) { return -EINVAL; } qemu_iovec_init_external(&qiov, &iov, 1); return bdrv_preadv(child, offset, &qiov); } int bdrv_pwritev(BdrvChild *child, int64_t offset, QEMUIOVector *qiov) { int ret; ret = bdrv_prwv_co(child, offset, qiov, true, 0); if (ret < 0) { return ret; } return qiov->size; } int bdrv_pwrite(BdrvChild *child, int64_t offset, const void *buf, int bytes) { QEMUIOVector qiov; struct iovec iov = { .iov_base = (void *) buf, .iov_len = bytes, }; if (bytes < 0) { return -EINVAL; } qemu_iovec_init_external(&qiov, &iov, 1); return bdrv_pwritev(child, offset, &qiov); } /* * Writes to the file and ensures that no writes are reordered across this * request (acts as a barrier) * * Returns 0 on success, -errno in error cases. */ int bdrv_pwrite_sync(BdrvChild *child, int64_t offset, const void *buf, int count) { int ret; ret = bdrv_pwrite(child, offset, buf, count); if (ret < 0) { return ret; } ret = bdrv_flush(child->bs); if (ret < 0) { return ret; } return 0; } typedef struct CoroutineIOCompletion { Coroutine *coroutine; int ret; } CoroutineIOCompletion; static void bdrv_co_io_em_complete(void *opaque, int ret) { CoroutineIOCompletion *co = opaque; co->ret = ret; aio_co_wake(co->coroutine); } static int coroutine_fn bdrv_driver_preadv(BlockDriverState *bs, uint64_t offset, uint64_t bytes, QEMUIOVector *qiov, int flags) { BlockDriver *drv = bs->drv; int64_t sector_num; unsigned int nb_sectors; assert(!(flags & ~BDRV_REQ_MASK)); if (drv->bdrv_co_preadv) { return drv->bdrv_co_preadv(bs, offset, bytes, qiov, flags); } sector_num = offset >> BDRV_SECTOR_BITS; nb_sectors = bytes >> BDRV_SECTOR_BITS; assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0); assert((bytes & (BDRV_SECTOR_SIZE - 1)) == 0); assert((bytes >> BDRV_SECTOR_BITS) <= BDRV_REQUEST_MAX_SECTORS); if (drv->bdrv_co_readv) { return drv->bdrv_co_readv(bs, sector_num, nb_sectors, qiov); } else { BlockAIOCB *acb; CoroutineIOCompletion co = { .coroutine = qemu_coroutine_self(), }; acb = bs->drv->bdrv_aio_readv(bs, sector_num, qiov, nb_sectors, bdrv_co_io_em_complete, &co); if (acb == NULL) { return -EIO; } else { qemu_coroutine_yield(); return co.ret; } } } static int coroutine_fn bdrv_driver_pwritev(BlockDriverState *bs, uint64_t offset, uint64_t bytes, QEMUIOVector *qiov, int flags) { BlockDriver *drv = bs->drv; int64_t sector_num; unsigned int nb_sectors; int ret; assert(!(flags & ~BDRV_REQ_MASK)); if (drv->bdrv_co_pwritev) { ret = drv->bdrv_co_pwritev(bs, offset, bytes, qiov, flags & bs->supported_write_flags); flags &= ~bs->supported_write_flags; goto emulate_flags; } sector_num = offset >> BDRV_SECTOR_BITS; nb_sectors = bytes >> BDRV_SECTOR_BITS; assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0); assert((bytes & (BDRV_SECTOR_SIZE - 1)) == 0); assert((bytes >> BDRV_SECTOR_BITS) <= BDRV_REQUEST_MAX_SECTORS); if (drv->bdrv_co_writev_flags) { ret = drv->bdrv_co_writev_flags(bs, sector_num, nb_sectors, qiov, flags & bs->supported_write_flags); flags &= ~bs->supported_write_flags; } else if (drv->bdrv_co_writev) { assert(!bs->supported_write_flags); ret = drv->bdrv_co_writev(bs, sector_num, nb_sectors, qiov); } else { BlockAIOCB *acb; CoroutineIOCompletion co = { .coroutine = qemu_coroutine_self(), }; acb = bs->drv->bdrv_aio_writev(bs, sector_num, qiov, nb_sectors, bdrv_co_io_em_complete, &co); if (acb == NULL) { ret = -EIO; } else { qemu_coroutine_yield(); ret = co.ret; } } emulate_flags: if (ret == 0 && (flags & BDRV_REQ_FUA)) { ret = bdrv_co_flush(bs); } return ret; } static int coroutine_fn bdrv_driver_pwritev_compressed(BlockDriverState *bs, uint64_t offset, uint64_t bytes, QEMUIOVector *qiov) { BlockDriver *drv = bs->drv; if (!drv->bdrv_co_pwritev_compressed) { return -ENOTSUP; } return drv->bdrv_co_pwritev_compressed(bs, offset, bytes, qiov); } static int coroutine_fn bdrv_co_do_copy_on_readv(BlockDriverState *bs, int64_t offset, unsigned int bytes, QEMUIOVector *qiov) { /* Perform I/O through a temporary buffer so that users who scribble over * their read buffer while the operation is in progress do not end up * modifying the image file. This is critical for zero-copy guest I/O * where anything might happen inside guest memory. */ void *bounce_buffer; BlockDriver *drv = bs->drv; struct iovec iov; QEMUIOVector bounce_qiov; int64_t cluster_offset; unsigned int cluster_bytes; size_t skip_bytes; int ret; /* Cover entire cluster so no additional backing file I/O is required when * allocating cluster in the image file. */ bdrv_round_to_clusters(bs, offset, bytes, &cluster_offset, &cluster_bytes); trace_bdrv_co_do_copy_on_readv(bs, offset, bytes, cluster_offset, cluster_bytes); iov.iov_len = cluster_bytes; iov.iov_base = bounce_buffer = qemu_try_blockalign(bs, iov.iov_len); if (bounce_buffer == NULL) { ret = -ENOMEM; goto err; } qemu_iovec_init_external(&bounce_qiov, &iov, 1); ret = bdrv_driver_preadv(bs, cluster_offset, cluster_bytes, &bounce_qiov, 0); if (ret < 0) { goto err; } if (drv->bdrv_co_pwrite_zeroes && buffer_is_zero(bounce_buffer, iov.iov_len)) { /* FIXME: Should we (perhaps conditionally) be setting * BDRV_REQ_MAY_UNMAP, if it will allow for a sparser copy * that still correctly reads as zero? */ ret = bdrv_co_do_pwrite_zeroes(bs, cluster_offset, cluster_bytes, 0); } else { /* This does not change the data on the disk, it is not necessary * to flush even in cache=writethrough mode. */ ret = bdrv_driver_pwritev(bs, cluster_offset, cluster_bytes, &bounce_qiov, 0); } if (ret < 0) { /* It might be okay to ignore write errors for guest requests. If this * is a deliberate copy-on-read then we don't want to ignore the error. * Simply report it in all cases. */ goto err; } skip_bytes = offset - cluster_offset; qemu_iovec_from_buf(qiov, 0, bounce_buffer + skip_bytes, bytes); err: qemu_vfree(bounce_buffer); return ret; } /* * Forwards an already correctly aligned request to the BlockDriver. This * handles copy on read, zeroing after EOF, and fragmentation of large * reads; any other features must be implemented by the caller. */ static int coroutine_fn bdrv_aligned_preadv(BlockDriverState *bs, BdrvTrackedRequest *req, int64_t offset, unsigned int bytes, int64_t align, QEMUIOVector *qiov, int flags) { int64_t total_bytes, max_bytes; int ret = 0; uint64_t bytes_remaining = bytes; int max_transfer; assert(is_power_of_2(align)); assert((offset & (align - 1)) == 0); assert((bytes & (align - 1)) == 0); assert(!qiov || bytes == qiov->size); assert((bs->open_flags & BDRV_O_NO_IO) == 0); max_transfer = QEMU_ALIGN_DOWN(MIN_NON_ZERO(bs->bl.max_transfer, INT_MAX), align); /* TODO: We would need a per-BDS .supported_read_flags and * potential fallback support, if we ever implement any read flags * to pass through to drivers. For now, there aren't any * passthrough flags. */ assert(!(flags & ~(BDRV_REQ_NO_SERIALISING | BDRV_REQ_COPY_ON_READ))); /* Handle Copy on Read and associated serialisation */ if (flags & BDRV_REQ_COPY_ON_READ) { /* If we touch the same cluster it counts as an overlap. This * guarantees that allocating writes will be serialized and not race * with each other for the same cluster. For example, in copy-on-read * it ensures that the CoR read and write operations are atomic and * guest writes cannot interleave between them. */ mark_request_serialising(req, bdrv_get_cluster_size(bs)); } if (!(flags & BDRV_REQ_NO_SERIALISING)) { wait_serialising_requests(req); } if (flags & BDRV_REQ_COPY_ON_READ) { int64_t start_sector = offset >> BDRV_SECTOR_BITS; int64_t end_sector = DIV_ROUND_UP(offset + bytes, BDRV_SECTOR_SIZE); unsigned int nb_sectors = end_sector - start_sector; int pnum; ret = bdrv_is_allocated(bs, start_sector, nb_sectors, &pnum); if (ret < 0) { goto out; } if (!ret || pnum != nb_sectors) { ret = bdrv_co_do_copy_on_readv(bs, offset, bytes, qiov); goto out; } } /* Forward the request to the BlockDriver, possibly fragmenting it */ total_bytes = bdrv_getlength(bs); if (total_bytes < 0) { ret = total_bytes; goto out; } max_bytes = ROUND_UP(MAX(0, total_bytes - offset), align); if (bytes <= max_bytes && bytes <= max_transfer) { ret = bdrv_driver_preadv(bs, offset, bytes, qiov, 0); goto out; } while (bytes_remaining) { int num; if (max_bytes) { QEMUIOVector local_qiov; num = MIN(bytes_remaining, MIN(max_bytes, max_transfer)); assert(num); qemu_iovec_init(&local_qiov, qiov->niov); qemu_iovec_concat(&local_qiov, qiov, bytes - bytes_remaining, num); ret = bdrv_driver_preadv(bs, offset + bytes - bytes_remaining, num, &local_qiov, 0); max_bytes -= num; qemu_iovec_destroy(&local_qiov); } else { num = bytes_remaining; ret = qemu_iovec_memset(qiov, bytes - bytes_remaining, 0, bytes_remaining); } if (ret < 0) { goto out; } bytes_remaining -= num; } out: return ret < 0 ? ret : 0; } /* * Handle a read request in coroutine context */ int coroutine_fn bdrv_co_preadv(BdrvChild *child, int64_t offset, unsigned int bytes, QEMUIOVector *qiov, BdrvRequestFlags flags) { BlockDriverState *bs = child->bs; BlockDriver *drv = bs->drv; BdrvTrackedRequest req; uint64_t align = bs->bl.request_alignment; uint8_t *head_buf = NULL; uint8_t *tail_buf = NULL; QEMUIOVector local_qiov; bool use_local_qiov = false; int ret; if (!drv) { return -ENOMEDIUM; } ret = bdrv_check_byte_request(bs, offset, bytes); if (ret < 0) { return ret; } bdrv_inc_in_flight(bs); /* Don't do copy-on-read if we read data before write operation */ if (bs->copy_on_read && !(flags & BDRV_REQ_NO_SERIALISING)) { flags |= BDRV_REQ_COPY_ON_READ; } /* Align read if necessary by padding qiov */ if (offset & (align - 1)) { head_buf = qemu_blockalign(bs, align); qemu_iovec_init(&local_qiov, qiov->niov + 2); qemu_iovec_add(&local_qiov, head_buf, offset & (align - 1)); qemu_iovec_concat(&local_qiov, qiov, 0, qiov->size); use_local_qiov = true; bytes += offset & (align - 1); offset = offset & ~(align - 1); } if ((offset + bytes) & (align - 1)) { if (!use_local_qiov) { qemu_iovec_init(&local_qiov, qiov->niov + 1); qemu_iovec_concat(&local_qiov, qiov, 0, qiov->size); use_local_qiov = true; } tail_buf = qemu_blockalign(bs, align); qemu_iovec_add(&local_qiov, tail_buf, align - ((offset + bytes) & (align - 1))); bytes = ROUND_UP(bytes, align); } tracked_request_begin(&req, bs, offset, bytes, BDRV_TRACKED_READ); ret = bdrv_aligned_preadv(bs, &req, offset, bytes, align, use_local_qiov ? &local_qiov : qiov, flags); tracked_request_end(&req); bdrv_dec_in_flight(bs); if (use_local_qiov) { qemu_iovec_destroy(&local_qiov); qemu_vfree(head_buf); qemu_vfree(tail_buf); } return ret; } static int coroutine_fn bdrv_co_do_readv(BdrvChild *child, int64_t sector_num, int nb_sectors, QEMUIOVector *qiov, BdrvRequestFlags flags) { if (nb_sectors < 0 || nb_sectors > BDRV_REQUEST_MAX_SECTORS) { return -EINVAL; } return bdrv_co_preadv(child, sector_num << BDRV_SECTOR_BITS, nb_sectors << BDRV_SECTOR_BITS, qiov, flags); } int coroutine_fn bdrv_co_readv(BdrvChild *child, int64_t sector_num, int nb_sectors, QEMUIOVector *qiov) { trace_bdrv_co_readv(child->bs, sector_num, nb_sectors); return bdrv_co_do_readv(child, sector_num, nb_sectors, qiov, 0); } /* Maximum buffer for write zeroes fallback, in bytes */ #define MAX_WRITE_ZEROES_BOUNCE_BUFFER (32768 << BDRV_SECTOR_BITS) static int coroutine_fn bdrv_co_do_pwrite_zeroes(BlockDriverState *bs, int64_t offset, int count, BdrvRequestFlags flags) { BlockDriver *drv = bs->drv; QEMUIOVector qiov; struct iovec iov = {0}; int ret = 0; bool need_flush = false; int head = 0; int tail = 0; int max_write_zeroes = MIN_NON_ZERO(bs->bl.max_pwrite_zeroes, INT_MAX); int alignment = MAX(bs->bl.pwrite_zeroes_alignment, bs->bl.request_alignment); int max_transfer = MIN_NON_ZERO(bs->bl.max_transfer, MAX_WRITE_ZEROES_BOUNCE_BUFFER); assert(alignment % bs->bl.request_alignment == 0); head = offset % alignment; tail = (offset + count) % alignment; max_write_zeroes = QEMU_ALIGN_DOWN(max_write_zeroes, alignment); assert(max_write_zeroes >= bs->bl.request_alignment); while (count > 0 && !ret) { int num = count; /* Align request. Block drivers can expect the "bulk" of the request * to be aligned, and that unaligned requests do not cross cluster * boundaries. */ if (head) { /* Make a small request up to the first aligned sector. For * convenience, limit this request to max_transfer even if * we don't need to fall back to writes. */ num = MIN(MIN(count, max_transfer), alignment - head); head = (head + num) % alignment; assert(num < max_write_zeroes); } else if (tail && num > alignment) { /* Shorten the request to the last aligned sector. */ num -= tail; } /* limit request size */ if (num > max_write_zeroes) { num = max_write_zeroes; } ret = -ENOTSUP; /* First try the efficient write zeroes operation */ if (drv->bdrv_co_pwrite_zeroes) { ret = drv->bdrv_co_pwrite_zeroes(bs, offset, num, flags & bs->supported_zero_flags); if (ret != -ENOTSUP && (flags & BDRV_REQ_FUA) && !(bs->supported_zero_flags & BDRV_REQ_FUA)) { need_flush = true; } } else { assert(!bs->supported_zero_flags); } if (ret == -ENOTSUP) { /* Fall back to bounce buffer if write zeroes is unsupported */ BdrvRequestFlags write_flags = flags & ~BDRV_REQ_ZERO_WRITE; if ((flags & BDRV_REQ_FUA) && !(bs->supported_write_flags & BDRV_REQ_FUA)) { /* No need for bdrv_driver_pwrite() to do a fallback * flush on each chunk; use just one at the end */ write_flags &= ~BDRV_REQ_FUA; need_flush = true; } num = MIN(num, max_transfer); iov.iov_len = num; if (iov.iov_base == NULL) { iov.iov_base = qemu_try_blockalign(bs, num); if (iov.iov_base == NULL) { ret = -ENOMEM; goto fail; } memset(iov.iov_base, 0, num); } qemu_iovec_init_external(&qiov, &iov, 1); ret = bdrv_driver_pwritev(bs, offset, num, &qiov, write_flags); /* Keep bounce buffer around if it is big enough for all * all future requests. */ if (num < max_transfer) { qemu_vfree(iov.iov_base); iov.iov_base = NULL; } } offset += num; count -= num; } fail: if (ret == 0 && need_flush) { ret = bdrv_co_flush(bs); } qemu_vfree(iov.iov_base); return ret; } /* * Forwards an already correctly aligned write request to the BlockDriver, * after possibly fragmenting it. */ static int coroutine_fn bdrv_aligned_pwritev(BlockDriverState *bs, BdrvTrackedRequest *req, int64_t offset, unsigned int bytes, int64_t align, QEMUIOVector *qiov, int flags) { BlockDriver *drv = bs->drv; bool waited; int ret; int64_t start_sector = offset >> BDRV_SECTOR_BITS; int64_t end_sector = DIV_ROUND_UP(offset + bytes, BDRV_SECTOR_SIZE); uint64_t bytes_remaining = bytes; int max_transfer; assert(is_power_of_2(align)); assert((offset & (align - 1)) == 0); assert((bytes & (align - 1)) == 0); assert(!qiov || bytes == qiov->size); assert((bs->open_flags & BDRV_O_NO_IO) == 0); assert(!(flags & ~BDRV_REQ_MASK)); max_transfer = QEMU_ALIGN_DOWN(MIN_NON_ZERO(bs->bl.max_transfer, INT_MAX), align); waited = wait_serialising_requests(req); assert(!waited || !req->serialising); assert(req->overlap_offset <= offset); assert(offset + bytes <= req->overlap_offset + req->overlap_bytes); ret = notifier_with_return_list_notify(&bs->before_write_notifiers, req); if (!ret && bs->detect_zeroes != BLOCKDEV_DETECT_ZEROES_OPTIONS_OFF && !(flags & BDRV_REQ_ZERO_WRITE) && drv->bdrv_co_pwrite_zeroes && qemu_iovec_is_zero(qiov)) { flags |= BDRV_REQ_ZERO_WRITE; if (bs->detect_zeroes == BLOCKDEV_DETECT_ZEROES_OPTIONS_UNMAP) { flags |= BDRV_REQ_MAY_UNMAP; } } if (ret < 0) { /* Do nothing, write notifier decided to fail this request */ } else if (flags & BDRV_REQ_ZERO_WRITE) { bdrv_debug_event(bs, BLKDBG_PWRITEV_ZERO); ret = bdrv_co_do_pwrite_zeroes(bs, offset, bytes, flags); } else if (flags & BDRV_REQ_WRITE_COMPRESSED) { ret = bdrv_driver_pwritev_compressed(bs, offset, bytes, qiov); } else if (bytes <= max_transfer) { bdrv_debug_event(bs, BLKDBG_PWRITEV); ret = bdrv_driver_pwritev(bs, offset, bytes, qiov, flags); } else { bdrv_debug_event(bs, BLKDBG_PWRITEV); while (bytes_remaining) { int num = MIN(bytes_remaining, max_transfer); QEMUIOVector local_qiov; int local_flags = flags; assert(num); if (num < bytes_remaining && (flags & BDRV_REQ_FUA) && !(bs->supported_write_flags & BDRV_REQ_FUA)) { /* If FUA is going to be emulated by flush, we only * need to flush on the last iteration */ local_flags &= ~BDRV_REQ_FUA; } qemu_iovec_init(&local_qiov, qiov->niov); qemu_iovec_concat(&local_qiov, qiov, bytes - bytes_remaining, num); ret = bdrv_driver_pwritev(bs, offset + bytes - bytes_remaining, num, &local_qiov, local_flags); qemu_iovec_destroy(&local_qiov); if (ret < 0) { break; } bytes_remaining -= num; } } bdrv_debug_event(bs, BLKDBG_PWRITEV_DONE); ++bs->write_gen; bdrv_set_dirty(bs, start_sector, end_sector - start_sector); if (bs->wr_highest_offset < offset + bytes) { bs->wr_highest_offset = offset + bytes; } if (ret >= 0) { bs->total_sectors = MAX(bs->total_sectors, end_sector); ret = 0; } return ret; } static int coroutine_fn bdrv_co_do_zero_pwritev(BlockDriverState *bs, int64_t offset, unsigned int bytes, BdrvRequestFlags flags, BdrvTrackedRequest *req) { uint8_t *buf = NULL; QEMUIOVector local_qiov; struct iovec iov; uint64_t align = bs->bl.request_alignment; unsigned int head_padding_bytes, tail_padding_bytes; int ret = 0; head_padding_bytes = offset & (align - 1); tail_padding_bytes = align - ((offset + bytes) & (align - 1)); assert(flags & BDRV_REQ_ZERO_WRITE); if (head_padding_bytes || tail_padding_bytes) { buf = qemu_blockalign(bs, align); iov = (struct iovec) { .iov_base = buf, .iov_len = align, }; qemu_iovec_init_external(&local_qiov, &iov, 1); } if (head_padding_bytes) { uint64_t zero_bytes = MIN(bytes, align - head_padding_bytes); /* RMW the unaligned part before head. */ mark_request_serialising(req, align); wait_serialising_requests(req); bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_HEAD); ret = bdrv_aligned_preadv(bs, req, offset & ~(align - 1), align, align, &local_qiov, 0); if (ret < 0) { goto fail; } bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_HEAD); memset(buf + head_padding_bytes, 0, zero_bytes); ret = bdrv_aligned_pwritev(bs, req, offset & ~(align - 1), align, align, &local_qiov, flags & ~BDRV_REQ_ZERO_WRITE); if (ret < 0) { goto fail; } offset += zero_bytes; bytes -= zero_bytes; } assert(!bytes || (offset & (align - 1)) == 0); if (bytes >= align) { /* Write the aligned part in the middle. */ uint64_t aligned_bytes = bytes & ~(align - 1); ret = bdrv_aligned_pwritev(bs, req, offset, aligned_bytes, align, NULL, flags); if (ret < 0) { goto fail; } bytes -= aligned_bytes; offset += aligned_bytes; } assert(!bytes || (offset & (align - 1)) == 0); if (bytes) { assert(align == tail_padding_bytes + bytes); /* RMW the unaligned part after tail. */ mark_request_serialising(req, align); wait_serialising_requests(req); bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_TAIL); ret = bdrv_aligned_preadv(bs, req, offset, align, align, &local_qiov, 0); if (ret < 0) { goto fail; } bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_TAIL); memset(buf, 0, bytes); ret = bdrv_aligned_pwritev(bs, req, offset, align, align, &local_qiov, flags & ~BDRV_REQ_ZERO_WRITE); } fail: qemu_vfree(buf); return ret; } /* * Handle a write request in coroutine context */ int coroutine_fn bdrv_co_pwritev(BdrvChild *child, int64_t offset, unsigned int bytes, QEMUIOVector *qiov, BdrvRequestFlags flags) { BlockDriverState *bs = child->bs; BdrvTrackedRequest req; uint64_t align = bs->bl.request_alignment; uint8_t *head_buf = NULL; uint8_t *tail_buf = NULL; QEMUIOVector local_qiov; bool use_local_qiov = false; int ret; if (!bs->drv) { return -ENOMEDIUM; } if (bs->read_only) { return -EPERM; } assert(!(bs->open_flags & BDRV_O_INACTIVE)); ret = bdrv_check_byte_request(bs, offset, bytes); if (ret < 0) { return ret; } bdrv_inc_in_flight(bs); /* * Align write if necessary by performing a read-modify-write cycle. * Pad qiov with the read parts and be sure to have a tracked request not * only for bdrv_aligned_pwritev, but also for the reads of the RMW cycle. */ tracked_request_begin(&req, bs, offset, bytes, BDRV_TRACKED_WRITE); if (!qiov) { ret = bdrv_co_do_zero_pwritev(bs, offset, bytes, flags, &req); goto out; } if (offset & (align - 1)) { QEMUIOVector head_qiov; struct iovec head_iov; mark_request_serialising(&req, align); wait_serialising_requests(&req); head_buf = qemu_blockalign(bs, align); head_iov = (struct iovec) { .iov_base = head_buf, .iov_len = align, }; qemu_iovec_init_external(&head_qiov, &head_iov, 1); bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_HEAD); ret = bdrv_aligned_preadv(bs, &req, offset & ~(align - 1), align, align, &head_qiov, 0); if (ret < 0) { goto fail; } bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_HEAD); qemu_iovec_init(&local_qiov, qiov->niov + 2); qemu_iovec_add(&local_qiov, head_buf, offset & (align - 1)); qemu_iovec_concat(&local_qiov, qiov, 0, qiov->size); use_local_qiov = true; bytes += offset & (align - 1); offset = offset & ~(align - 1); /* We have read the tail already if the request is smaller * than one aligned block. */ if (bytes < align) { qemu_iovec_add(&local_qiov, head_buf + bytes, align - bytes); bytes = align; } } if ((offset + bytes) & (align - 1)) { QEMUIOVector tail_qiov; struct iovec tail_iov; size_t tail_bytes; bool waited; mark_request_serialising(&req, align); waited = wait_serialising_requests(&req); assert(!waited || !use_local_qiov); tail_buf = qemu_blockalign(bs, align); tail_iov = (struct iovec) { .iov_base = tail_buf, .iov_len = align, }; qemu_iovec_init_external(&tail_qiov, &tail_iov, 1); bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_TAIL); ret = bdrv_aligned_preadv(bs, &req, (offset + bytes) & ~(align - 1), align, align, &tail_qiov, 0); if (ret < 0) { goto fail; } bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_TAIL); if (!use_local_qiov) { qemu_iovec_init(&local_qiov, qiov->niov + 1); qemu_iovec_concat(&local_qiov, qiov, 0, qiov->size); use_local_qiov = true; } tail_bytes = (offset + bytes) & (align - 1); qemu_iovec_add(&local_qiov, tail_buf + tail_bytes, align - tail_bytes); bytes = ROUND_UP(bytes, align); } ret = bdrv_aligned_pwritev(bs, &req, offset, bytes, align, use_local_qiov ? &local_qiov : qiov, flags); fail: if (use_local_qiov) { qemu_iovec_destroy(&local_qiov); } qemu_vfree(head_buf); qemu_vfree(tail_buf); out: tracked_request_end(&req); bdrv_dec_in_flight(bs); return ret; } static int coroutine_fn bdrv_co_do_writev(BdrvChild *child, int64_t sector_num, int nb_sectors, QEMUIOVector *qiov, BdrvRequestFlags flags) { if (nb_sectors < 0 || nb_sectors > BDRV_REQUEST_MAX_SECTORS) { return -EINVAL; } return bdrv_co_pwritev(child, sector_num << BDRV_SECTOR_BITS, nb_sectors << BDRV_SECTOR_BITS, qiov, flags); } int coroutine_fn bdrv_co_writev(BdrvChild *child, int64_t sector_num, int nb_sectors, QEMUIOVector *qiov) { trace_bdrv_co_writev(child->bs, sector_num, nb_sectors); return bdrv_co_do_writev(child, sector_num, nb_sectors, qiov, 0); } int coroutine_fn bdrv_co_pwrite_zeroes(BdrvChild *child, int64_t offset, int count, BdrvRequestFlags flags) { trace_bdrv_co_pwrite_zeroes(child->bs, offset, count, flags); if (!(child->bs->open_flags & BDRV_O_UNMAP)) { flags &= ~BDRV_REQ_MAY_UNMAP; } return bdrv_co_pwritev(child, offset, count, NULL, BDRV_REQ_ZERO_WRITE | flags); } /* * Flush ALL BDSes regardless of if they are reachable via a BlkBackend or not. */ int bdrv_flush_all(void) { BdrvNextIterator it; BlockDriverState *bs = NULL; int result = 0; for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) { AioContext *aio_context = bdrv_get_aio_context(bs); int ret; aio_context_acquire(aio_context); ret = bdrv_flush(bs); if (ret < 0 && !result) { result = ret; } aio_context_release(aio_context); } return result; } typedef struct BdrvCoGetBlockStatusData { BlockDriverState *bs; BlockDriverState *base; BlockDriverState **file; int64_t sector_num; int nb_sectors; int *pnum; int64_t ret; bool done; } BdrvCoGetBlockStatusData; /* * Returns the allocation status of the specified sectors. * Drivers not implementing the functionality are assumed to not support * backing files, hence all their sectors are reported as allocated. * * If 'sector_num' is beyond the end of the disk image the return value is 0 * and 'pnum' is set to 0. * * 'pnum' is set to the number of sectors (including and immediately following * the specified sector) that are known to be in the same * allocated/unallocated state. * * 'nb_sectors' is the max value 'pnum' should be set to. If nb_sectors goes * beyond the end of the disk image it will be clamped. * * If returned value is positive and BDRV_BLOCK_OFFSET_VALID bit is set, 'file' * points to the BDS which the sector range is allocated in. */ static int64_t coroutine_fn bdrv_co_get_block_status(BlockDriverState *bs, int64_t sector_num, int nb_sectors, int *pnum, BlockDriverState **file) { int64_t total_sectors; int64_t n; int64_t ret, ret2; total_sectors = bdrv_nb_sectors(bs); if (total_sectors < 0) { return total_sectors; } if (sector_num >= total_sectors) { *pnum = 0; return 0; } n = total_sectors - sector_num; if (n < nb_sectors) { nb_sectors = n; } if (!bs->drv->bdrv_co_get_block_status) { *pnum = nb_sectors; ret = BDRV_BLOCK_DATA | BDRV_BLOCK_ALLOCATED; if (bs->drv->protocol_name) { ret |= BDRV_BLOCK_OFFSET_VALID | (sector_num * BDRV_SECTOR_SIZE); } return ret; } *file = NULL; bdrv_inc_in_flight(bs); ret = bs->drv->bdrv_co_get_block_status(bs, sector_num, nb_sectors, pnum, file); if (ret < 0) { *pnum = 0; goto out; } if (ret & BDRV_BLOCK_RAW) { assert(ret & BDRV_BLOCK_OFFSET_VALID); ret = bdrv_get_block_status(bs->file->bs, ret >> BDRV_SECTOR_BITS, *pnum, pnum, file); goto out; } if (ret & (BDRV_BLOCK_DATA | BDRV_BLOCK_ZERO)) { ret |= BDRV_BLOCK_ALLOCATED; } else { if (bdrv_unallocated_blocks_are_zero(bs)) { ret |= BDRV_BLOCK_ZERO; } else if (bs->backing) { BlockDriverState *bs2 = bs->backing->bs; int64_t nb_sectors2 = bdrv_nb_sectors(bs2); if (nb_sectors2 >= 0 && sector_num >= nb_sectors2) { ret |= BDRV_BLOCK_ZERO; } } } if (*file && *file != bs && (ret & BDRV_BLOCK_DATA) && !(ret & BDRV_BLOCK_ZERO) && (ret & BDRV_BLOCK_OFFSET_VALID)) { BlockDriverState *file2; int file_pnum; ret2 = bdrv_co_get_block_status(*file, ret >> BDRV_SECTOR_BITS, *pnum, &file_pnum, &file2); if (ret2 >= 0) { /* Ignore errors. This is just providing extra information, it * is useful but not necessary. */ if (!file_pnum) { /* !file_pnum indicates an offset at or beyond the EOF; it is * perfectly valid for the format block driver to point to such * offsets, so catch it and mark everything as zero */ ret |= BDRV_BLOCK_ZERO; } else { /* Limit request to the range reported by the protocol driver */ *pnum = file_pnum; ret |= (ret2 & BDRV_BLOCK_ZERO); } } } out: bdrv_dec_in_flight(bs); return ret; } static int64_t coroutine_fn bdrv_co_get_block_status_above(BlockDriverState *bs, BlockDriverState *base, int64_t sector_num, int nb_sectors, int *pnum, BlockDriverState **file) { BlockDriverState *p; int64_t ret = 0; assert(bs != base); for (p = bs; p != base; p = backing_bs(p)) { ret = bdrv_co_get_block_status(p, sector_num, nb_sectors, pnum, file); if (ret < 0 || ret & BDRV_BLOCK_ALLOCATED) { break; } /* [sector_num, pnum] unallocated on this layer, which could be only * the first part of [sector_num, nb_sectors]. */ nb_sectors = MIN(nb_sectors, *pnum); } return ret; } /* Coroutine wrapper for bdrv_get_block_status_above() */ static void coroutine_fn bdrv_get_block_status_above_co_entry(void *opaque) { BdrvCoGetBlockStatusData *data = opaque; data->ret = bdrv_co_get_block_status_above(data->bs, data->base, data->sector_num, data->nb_sectors, data->pnum, data->file); data->done = true; } /* * Synchronous wrapper around bdrv_co_get_block_status_above(). * * See bdrv_co_get_block_status_above() for details. */ int64_t bdrv_get_block_status_above(BlockDriverState *bs, BlockDriverState *base, int64_t sector_num, int nb_sectors, int *pnum, BlockDriverState **file) { Coroutine *co; BdrvCoGetBlockStatusData data = { .bs = bs, .base = base, .file = file, .sector_num = sector_num, .nb_sectors = nb_sectors, .pnum = pnum, .done = false, }; if (qemu_in_coroutine()) { /* Fast-path if already in coroutine context */ bdrv_get_block_status_above_co_entry(&data); } else { co = qemu_coroutine_create(bdrv_get_block_status_above_co_entry, &data); qemu_coroutine_enter(co); BDRV_POLL_WHILE(bs, !data.done); } return data.ret; } int64_t bdrv_get_block_status(BlockDriverState *bs, int64_t sector_num, int nb_sectors, int *pnum, BlockDriverState **file) { return bdrv_get_block_status_above(bs, backing_bs(bs), sector_num, nb_sectors, pnum, file); } int coroutine_fn bdrv_is_allocated(BlockDriverState *bs, int64_t sector_num, int nb_sectors, int *pnum) { BlockDriverState *file; int64_t ret = bdrv_get_block_status(bs, sector_num, nb_sectors, pnum, &file); if (ret < 0) { return ret; } return !!(ret & BDRV_BLOCK_ALLOCATED); } /* * Given an image chain: ... -> [BASE] -> [INTER1] -> [INTER2] -> [TOP] * * Return true if the given sector is allocated in any image between * BASE and TOP (inclusive). BASE can be NULL to check if the given * sector is allocated in any image of the chain. Return false otherwise. * * 'pnum' is set to the number of sectors (including and immediately following * the specified sector) that are known to be in the same * allocated/unallocated state. * */ int bdrv_is_allocated_above(BlockDriverState *top, BlockDriverState *base, int64_t sector_num, int nb_sectors, int *pnum) { BlockDriverState *intermediate; int ret, n = nb_sectors; intermediate = top; while (intermediate && intermediate != base) { int pnum_inter; ret = bdrv_is_allocated(intermediate, sector_num, nb_sectors, &pnum_inter); if (ret < 0) { return ret; } else if (ret) { *pnum = pnum_inter; return 1; } /* * [sector_num, nb_sectors] is unallocated on top but intermediate * might have * * [sector_num+x, nr_sectors] allocated. */ if (n > pnum_inter && (intermediate == top || sector_num + pnum_inter < intermediate->total_sectors)) { n = pnum_inter; } intermediate = backing_bs(intermediate); } *pnum = n; return 0; } typedef struct BdrvVmstateCo { BlockDriverState *bs; QEMUIOVector *qiov; int64_t pos; bool is_read; int ret; } BdrvVmstateCo; static int coroutine_fn bdrv_co_rw_vmstate(BlockDriverState *bs, QEMUIOVector *qiov, int64_t pos, bool is_read) { BlockDriver *drv = bs->drv; if (!drv) { return -ENOMEDIUM; } else if (drv->bdrv_load_vmstate) { return is_read ? drv->bdrv_load_vmstate(bs, qiov, pos) : drv->bdrv_save_vmstate(bs, qiov, pos); } else if (bs->file) { return bdrv_co_rw_vmstate(bs->file->bs, qiov, pos, is_read); } return -ENOTSUP; } static void coroutine_fn bdrv_co_rw_vmstate_entry(void *opaque) { BdrvVmstateCo *co = opaque; co->ret = bdrv_co_rw_vmstate(co->bs, co->qiov, co->pos, co->is_read); } static inline int bdrv_rw_vmstate(BlockDriverState *bs, QEMUIOVector *qiov, int64_t pos, bool is_read) { if (qemu_in_coroutine()) { return bdrv_co_rw_vmstate(bs, qiov, pos, is_read); } else { BdrvVmstateCo data = { .bs = bs, .qiov = qiov, .pos = pos, .is_read = is_read, .ret = -EINPROGRESS, }; Coroutine *co = qemu_coroutine_create(bdrv_co_rw_vmstate_entry, &data); qemu_coroutine_enter(co); while (data.ret == -EINPROGRESS) { aio_poll(bdrv_get_aio_context(bs), true); } return data.ret; } } int bdrv_save_vmstate(BlockDriverState *bs, const uint8_t *buf, int64_t pos, int size) { QEMUIOVector qiov; struct iovec iov = { .iov_base = (void *) buf, .iov_len = size, }; int ret; qemu_iovec_init_external(&qiov, &iov, 1); ret = bdrv_writev_vmstate(bs, &qiov, pos); if (ret < 0) { return ret; } return size; } int bdrv_writev_vmstate(BlockDriverState *bs, QEMUIOVector *qiov, int64_t pos) { return bdrv_rw_vmstate(bs, qiov, pos, false); } int bdrv_load_vmstate(BlockDriverState *bs, uint8_t *buf, int64_t pos, int size) { QEMUIOVector qiov; struct iovec iov = { .iov_base = buf, .iov_len = size, }; int ret; qemu_iovec_init_external(&qiov, &iov, 1); ret = bdrv_readv_vmstate(bs, &qiov, pos); if (ret < 0) { return ret; } return size; } int bdrv_readv_vmstate(BlockDriverState *bs, QEMUIOVector *qiov, int64_t pos) { return bdrv_rw_vmstate(bs, qiov, pos, true); } /**************************************************************/ /* async I/Os */ BlockAIOCB *bdrv_aio_readv(BdrvChild *child, int64_t sector_num, QEMUIOVector *qiov, int nb_sectors, BlockCompletionFunc *cb, void *opaque) { trace_bdrv_aio_readv(child->bs, sector_num, nb_sectors, opaque); assert(nb_sectors << BDRV_SECTOR_BITS == qiov->size); return bdrv_co_aio_prw_vector(child, sector_num << BDRV_SECTOR_BITS, qiov, 0, cb, opaque, false); } BlockAIOCB *bdrv_aio_writev(BdrvChild *child, int64_t sector_num, QEMUIOVector *qiov, int nb_sectors, BlockCompletionFunc *cb, void *opaque) { trace_bdrv_aio_writev(child->bs, sector_num, nb_sectors, opaque); assert(nb_sectors << BDRV_SECTOR_BITS == qiov->size); return bdrv_co_aio_prw_vector(child, sector_num << BDRV_SECTOR_BITS, qiov, 0, cb, opaque, true); } void bdrv_aio_cancel(BlockAIOCB *acb) { qemu_aio_ref(acb); bdrv_aio_cancel_async(acb); while (acb->refcnt > 1) { if (acb->aiocb_info->get_aio_context) { aio_poll(acb->aiocb_info->get_aio_context(acb), true); } else if (acb->bs) { /* qemu_aio_ref and qemu_aio_unref are not thread-safe, so * assert that we're not using an I/O thread. Thread-safe * code should use bdrv_aio_cancel_async exclusively. */ assert(bdrv_get_aio_context(acb->bs) == qemu_get_aio_context()); aio_poll(bdrv_get_aio_context(acb->bs), true); } else { abort(); } } qemu_aio_unref(acb); } /* Async version of aio cancel. The caller is not blocked if the acb implements * cancel_async, otherwise we do nothing and let the request normally complete. * In either case the completion callback must be called. */ void bdrv_aio_cancel_async(BlockAIOCB *acb) { if (acb->aiocb_info->cancel_async) { acb->aiocb_info->cancel_async(acb); } } /**************************************************************/ /* async block device emulation */ typedef struct BlockRequest { union { /* Used during read, write, trim */ struct { int64_t offset; int bytes; int flags; QEMUIOVector *qiov; }; /* Used during ioctl */ struct { int req; void *buf; }; }; BlockCompletionFunc *cb; void *opaque; int error; } BlockRequest; typedef struct BlockAIOCBCoroutine { BlockAIOCB common; BdrvChild *child; BlockRequest req; bool is_write; bool need_bh; bool *done; } BlockAIOCBCoroutine; static const AIOCBInfo bdrv_em_co_aiocb_info = { .aiocb_size = sizeof(BlockAIOCBCoroutine), }; static void bdrv_co_complete(BlockAIOCBCoroutine *acb) { if (!acb->need_bh) { bdrv_dec_in_flight(acb->common.bs); acb->common.cb(acb->common.opaque, acb->req.error); qemu_aio_unref(acb); } } static void bdrv_co_em_bh(void *opaque) { BlockAIOCBCoroutine *acb = opaque; assert(!acb->need_bh); bdrv_co_complete(acb); } static void bdrv_co_maybe_schedule_bh(BlockAIOCBCoroutine *acb) { acb->need_bh = false; if (acb->req.error != -EINPROGRESS) { BlockDriverState *bs = acb->common.bs; aio_bh_schedule_oneshot(bdrv_get_aio_context(bs), bdrv_co_em_bh, acb); } } /* Invoke bdrv_co_do_readv/bdrv_co_do_writev */ static void coroutine_fn bdrv_co_do_rw(void *opaque) { BlockAIOCBCoroutine *acb = opaque; if (!acb->is_write) { acb->req.error = bdrv_co_preadv(acb->child, acb->req.offset, acb->req.qiov->size, acb->req.qiov, acb->req.flags); } else { acb->req.error = bdrv_co_pwritev(acb->child, acb->req.offset, acb->req.qiov->size, acb->req.qiov, acb->req.flags); } bdrv_co_complete(acb); } static BlockAIOCB *bdrv_co_aio_prw_vector(BdrvChild *child, int64_t offset, QEMUIOVector *qiov, BdrvRequestFlags flags, BlockCompletionFunc *cb, void *opaque, bool is_write) { Coroutine *co; BlockAIOCBCoroutine *acb; /* Matched by bdrv_co_complete's bdrv_dec_in_flight. */ bdrv_inc_in_flight(child->bs); acb = qemu_aio_get(&bdrv_em_co_aiocb_info, child->bs, cb, opaque); acb->child = child; acb->need_bh = true; acb->req.error = -EINPROGRESS; acb->req.offset = offset; acb->req.qiov = qiov; acb->req.flags = flags; acb->is_write = is_write; co = qemu_coroutine_create(bdrv_co_do_rw, acb); qemu_coroutine_enter(co); bdrv_co_maybe_schedule_bh(acb); return &acb->common; } static void coroutine_fn bdrv_aio_flush_co_entry(void *opaque) { BlockAIOCBCoroutine *acb = opaque; BlockDriverState *bs = acb->common.bs; acb->req.error = bdrv_co_flush(bs); bdrv_co_complete(acb); } BlockAIOCB *bdrv_aio_flush(BlockDriverState *bs, BlockCompletionFunc *cb, void *opaque) { trace_bdrv_aio_flush(bs, opaque); Coroutine *co; BlockAIOCBCoroutine *acb; /* Matched by bdrv_co_complete's bdrv_dec_in_flight. */ bdrv_inc_in_flight(bs); acb = qemu_aio_get(&bdrv_em_co_aiocb_info, bs, cb, opaque); acb->need_bh = true; acb->req.error = -EINPROGRESS; co = qemu_coroutine_create(bdrv_aio_flush_co_entry, acb); qemu_coroutine_enter(co); bdrv_co_maybe_schedule_bh(acb); return &acb->common; } /**************************************************************/ /* Coroutine block device emulation */ typedef struct FlushCo { BlockDriverState *bs; int ret; } FlushCo; static void coroutine_fn bdrv_flush_co_entry(void *opaque) { FlushCo *rwco = opaque; rwco->ret = bdrv_co_flush(rwco->bs); } int coroutine_fn bdrv_co_flush(BlockDriverState *bs) { int ret; if (!bs || !bdrv_is_inserted(bs) || bdrv_is_read_only(bs) || bdrv_is_sg(bs)) { return 0; } bdrv_inc_in_flight(bs); int current_gen = bs->write_gen; /* Wait until any previous flushes are completed */ while (bs->active_flush_req) { qemu_co_queue_wait(&bs->flush_queue); } bs->active_flush_req = true; /* Write back all layers by calling one driver function */ if (bs->drv->bdrv_co_flush) { ret = bs->drv->bdrv_co_flush(bs); goto out; } /* Write back cached data to the OS even with cache=unsafe */ BLKDBG_EVENT(bs->file, BLKDBG_FLUSH_TO_OS); if (bs->drv->bdrv_co_flush_to_os) { ret = bs->drv->bdrv_co_flush_to_os(bs); if (ret < 0) { goto out; } } /* But don't actually force it to the disk with cache=unsafe */ if (bs->open_flags & BDRV_O_NO_FLUSH) { goto flush_parent; } /* Check if we really need to flush anything */ if (bs->flushed_gen == current_gen) { goto flush_parent; } BLKDBG_EVENT(bs->file, BLKDBG_FLUSH_TO_DISK); if (bs->drv->bdrv_co_flush_to_disk) { ret = bs->drv->bdrv_co_flush_to_disk(bs); } else if (bs->drv->bdrv_aio_flush) { BlockAIOCB *acb; CoroutineIOCompletion co = { .coroutine = qemu_coroutine_self(), }; acb = bs->drv->bdrv_aio_flush(bs, bdrv_co_io_em_complete, &co); if (acb == NULL) { ret = -EIO; } else { qemu_coroutine_yield(); ret = co.ret; } } else { /* * Some block drivers always operate in either writethrough or unsafe * mode and don't support bdrv_flush therefore. Usually qemu doesn't * know how the server works (because the behaviour is hardcoded or * depends on server-side configuration), so we can't ensure that * everything is safe on disk. Returning an error doesn't work because * that would break guests even if the server operates in writethrough * mode. * * Let's hope the user knows what he's doing. */ ret = 0; } if (ret < 0) { goto out; } /* Now flush the underlying protocol. It will also have BDRV_O_NO_FLUSH * in the case of cache=unsafe, so there are no useless flushes. */ flush_parent: ret = bs->file ? bdrv_co_flush(bs->file->bs) : 0; out: /* Notify any pending flushes that we have completed */ if (ret == 0) { bs->flushed_gen = current_gen; } bs->active_flush_req = false; /* Return value is ignored - it's ok if wait queue is empty */ qemu_co_queue_next(&bs->flush_queue); bdrv_dec_in_flight(bs); return ret; } int bdrv_flush(BlockDriverState *bs) { Coroutine *co; FlushCo flush_co = { .bs = bs, .ret = NOT_DONE, }; if (qemu_in_coroutine()) { /* Fast-path if already in coroutine context */ bdrv_flush_co_entry(&flush_co); } else { co = qemu_coroutine_create(bdrv_flush_co_entry, &flush_co); qemu_coroutine_enter(co); BDRV_POLL_WHILE(bs, flush_co.ret == NOT_DONE); } return flush_co.ret; } typedef struct DiscardCo { BlockDriverState *bs; int64_t offset; int count; int ret; } DiscardCo; static void coroutine_fn bdrv_pdiscard_co_entry(void *opaque) { DiscardCo *rwco = opaque; rwco->ret = bdrv_co_pdiscard(rwco->bs, rwco->offset, rwco->count); } int coroutine_fn bdrv_co_pdiscard(BlockDriverState *bs, int64_t offset, int count) { BdrvTrackedRequest req; int max_pdiscard, ret; int head, tail, align; if (!bs->drv) { return -ENOMEDIUM; } ret = bdrv_check_byte_request(bs, offset, count); if (ret < 0) { return ret; } else if (bs->read_only) { return -EPERM; } assert(!(bs->open_flags & BDRV_O_INACTIVE)); /* Do nothing if disabled. */ if (!(bs->open_flags & BDRV_O_UNMAP)) { return 0; } if (!bs->drv->bdrv_co_pdiscard && !bs->drv->bdrv_aio_pdiscard) { return 0; } /* Discard is advisory, but some devices track and coalesce * unaligned requests, so we must pass everything down rather than * round here. Still, most devices will just silently ignore * unaligned requests (by returning -ENOTSUP), so we must fragment * the request accordingly. */ align = MAX(bs->bl.pdiscard_alignment, bs->bl.request_alignment); assert(align % bs->bl.request_alignment == 0); head = offset % align; tail = (offset + count) % align; bdrv_inc_in_flight(bs); tracked_request_begin(&req, bs, offset, count, BDRV_TRACKED_DISCARD); ret = notifier_with_return_list_notify(&bs->before_write_notifiers, &req); if (ret < 0) { goto out; } max_pdiscard = QEMU_ALIGN_DOWN(MIN_NON_ZERO(bs->bl.max_pdiscard, INT_MAX), align); assert(max_pdiscard >= bs->bl.request_alignment); while (count > 0) { int ret; int num = count; if (head) { /* Make small requests to get to alignment boundaries. */ num = MIN(count, align - head); if (!QEMU_IS_ALIGNED(num, bs->bl.request_alignment)) { num %= bs->bl.request_alignment; } head = (head + num) % align; assert(num < max_pdiscard); } else if (tail) { if (num > align) { /* Shorten the request to the last aligned cluster. */ num -= tail; } else if (!QEMU_IS_ALIGNED(tail, bs->bl.request_alignment) && tail > bs->bl.request_alignment) { tail %= bs->bl.request_alignment; num -= tail; } } /* limit request size */ if (num > max_pdiscard) { num = max_pdiscard; } if (bs->drv->bdrv_co_pdiscard) { ret = bs->drv->bdrv_co_pdiscard(bs, offset, num); } else { BlockAIOCB *acb; CoroutineIOCompletion co = { .coroutine = qemu_coroutine_self(), }; acb = bs->drv->bdrv_aio_pdiscard(bs, offset, num, bdrv_co_io_em_complete, &co); if (acb == NULL) { ret = -EIO; goto out; } else { qemu_coroutine_yield(); ret = co.ret; } } if (ret && ret != -ENOTSUP) { goto out; } offset += num; count -= num; } ret = 0; out: ++bs->write_gen; bdrv_set_dirty(bs, req.offset >> BDRV_SECTOR_BITS, req.bytes >> BDRV_SECTOR_BITS); tracked_request_end(&req); bdrv_dec_in_flight(bs); return ret; } int bdrv_pdiscard(BlockDriverState *bs, int64_t offset, int count) { Coroutine *co; DiscardCo rwco = { .bs = bs, .offset = offset, .count = count, .ret = NOT_DONE, }; if (qemu_in_coroutine()) { /* Fast-path if already in coroutine context */ bdrv_pdiscard_co_entry(&rwco); } else { co = qemu_coroutine_create(bdrv_pdiscard_co_entry, &rwco); qemu_coroutine_enter(co); BDRV_POLL_WHILE(bs, rwco.ret == NOT_DONE); } return rwco.ret; } int bdrv_co_ioctl(BlockDriverState *bs, int req, void *buf) { BlockDriver *drv = bs->drv; CoroutineIOCompletion co = { .coroutine = qemu_coroutine_self(), }; BlockAIOCB *acb; bdrv_inc_in_flight(bs); if (!drv || (!drv->bdrv_aio_ioctl && !drv->bdrv_co_ioctl)) { co.ret = -ENOTSUP; goto out; } if (drv->bdrv_co_ioctl) { co.ret = drv->bdrv_co_ioctl(bs, req, buf); } else { acb = drv->bdrv_aio_ioctl(bs, req, buf, bdrv_co_io_em_complete, &co); if (!acb) { co.ret = -ENOTSUP; goto out; } qemu_coroutine_yield(); } out: bdrv_dec_in_flight(bs); return co.ret; } void *qemu_blockalign(BlockDriverState *bs, size_t size) { return qemu_memalign(bdrv_opt_mem_align(bs), size); } void *qemu_blockalign0(BlockDriverState *bs, size_t size) { return memset(qemu_blockalign(bs, size), 0, size); } void *qemu_try_blockalign(BlockDriverState *bs, size_t size) { size_t align = bdrv_opt_mem_align(bs); /* Ensure that NULL is never returned on success */ assert(align > 0); if (size == 0) { size = align; } return qemu_try_memalign(align, size); } void *qemu_try_blockalign0(BlockDriverState *bs, size_t size) { void *mem = qemu_try_blockalign(bs, size); if (mem) { memset(mem, 0, size); } return mem; } /* * Check if all memory in this vector is sector aligned. */ bool bdrv_qiov_is_aligned(BlockDriverState *bs, QEMUIOVector *qiov) { int i; size_t alignment = bdrv_min_mem_align(bs); for (i = 0; i < qiov->niov; i++) { if ((uintptr_t) qiov->iov[i].iov_base % alignment) { return false; } if (qiov->iov[i].iov_len % alignment) { return false; } } return true; } void bdrv_add_before_write_notifier(BlockDriverState *bs, NotifierWithReturn *notifier) { notifier_with_return_list_add(&bs->before_write_notifiers, notifier); } void bdrv_io_plug(BlockDriverState *bs) { BdrvChild *child; QLIST_FOREACH(child, &bs->children, next) { bdrv_io_plug(child->bs); } if (bs->io_plugged++ == 0) { BlockDriver *drv = bs->drv; if (drv && drv->bdrv_io_plug) { drv->bdrv_io_plug(bs); } } } void bdrv_io_unplug(BlockDriverState *bs) { BdrvChild *child; assert(bs->io_plugged); if (--bs->io_plugged == 0) { BlockDriver *drv = bs->drv; if (drv && drv->bdrv_io_unplug) { drv->bdrv_io_unplug(bs); } } QLIST_FOREACH(child, &bs->children, next) { bdrv_io_unplug(child->bs); } }