diff options
Diffstat (limited to 'block/io.c')
| -rw-r--r-- | block/io.c | 130 |
1 files changed, 76 insertions, 54 deletions
diff --git a/block/io.c b/block/io.c index 24205f5168..95b1c56c06 100644 --- a/block/io.c +++ b/block/io.c @@ -754,55 +754,65 @@ static bool tracked_request_overlaps(BdrvTrackedRequest *req, return true; } -static bool coroutine_fn -bdrv_wait_serialising_requests_locked(BlockDriverState *bs, - BdrvTrackedRequest *self) +/* Called with self->bs->reqs_lock held */ +static BdrvTrackedRequest * +bdrv_find_conflicting_request(BdrvTrackedRequest *self) { BdrvTrackedRequest *req; - bool retry; - bool waited = 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, &bs->reqs_lock); - self->waiting_for = NULL; - retry = true; - waited = true; - break; - } + QLIST_FOREACH(req, &self->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) { + return req; } } - } while (retry); + } + + return NULL; +} + +/* Called with self->bs->reqs_lock held */ +static bool coroutine_fn +bdrv_wait_serialising_requests_locked(BdrvTrackedRequest *self) +{ + BdrvTrackedRequest *req; + bool waited = false; + + while ((req = bdrv_find_conflicting_request(self))) { + self->waiting_for = req; + qemu_co_queue_wait(&req->wait_queue, &self->bs->reqs_lock); + self->waiting_for = NULL; + waited = true; + } + return waited; } -bool bdrv_mark_request_serialising(BdrvTrackedRequest *req, uint64_t align) +/* Called with req->bs->reqs_lock held */ +static void tracked_request_set_serialising(BdrvTrackedRequest *req, + uint64_t align) { - BlockDriverState *bs = req->bs; int64_t overlap_offset = req->offset & ~(align - 1); uint64_t overlap_bytes = ROUND_UP(req->offset + req->bytes, align) - overlap_offset; - bool waited; - qemu_co_mutex_lock(&bs->reqs_lock); if (!req->serialising) { qatomic_inc(&req->bs->serialising_in_flight); req->serialising = true; @@ -810,9 +820,6 @@ bool bdrv_mark_request_serialising(BdrvTrackedRequest *req, uint64_t align) req->overlap_offset = MIN(req->overlap_offset, overlap_offset); req->overlap_bytes = MAX(req->overlap_bytes, overlap_bytes); - waited = bdrv_wait_serialising_requests_locked(bs, req); - qemu_co_mutex_unlock(&bs->reqs_lock); - return waited; } /** @@ -892,12 +899,27 @@ static bool coroutine_fn bdrv_wait_serialising_requests(BdrvTrackedRequest *self } qemu_co_mutex_lock(&bs->reqs_lock); - waited = bdrv_wait_serialising_requests_locked(bs, self); + waited = bdrv_wait_serialising_requests_locked(self); qemu_co_mutex_unlock(&bs->reqs_lock); return waited; } +bool coroutine_fn bdrv_make_request_serialising(BdrvTrackedRequest *req, + uint64_t align) +{ + bool waited; + + qemu_co_mutex_lock(&req->bs->reqs_lock); + + tracked_request_set_serialising(req, align); + waited = bdrv_wait_serialising_requests_locked(req); + + qemu_co_mutex_unlock(&req->bs->reqs_lock); + + return waited; +} + int bdrv_check_request(int64_t offset, int64_t bytes) { if (offset < 0 || bytes < 0) { @@ -1423,7 +1445,7 @@ static int coroutine_fn bdrv_aligned_preadv(BdrvChild *child, * 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. */ - bdrv_mark_request_serialising(req, bdrv_get_cluster_size(bs)); + bdrv_make_request_serialising(req, bdrv_get_cluster_size(bs)); } else { bdrv_wait_serialising_requests(req); } @@ -1827,7 +1849,6 @@ bdrv_co_write_req_prepare(BdrvChild *child, int64_t offset, uint64_t bytes, BdrvTrackedRequest *req, int flags) { BlockDriverState *bs = child->bs; - bool waited; int64_t end_sector = DIV_ROUND_UP(offset + bytes, BDRV_SECTOR_SIZE); if (bs->read_only) { @@ -1837,17 +1858,18 @@ bdrv_co_write_req_prepare(BdrvChild *child, int64_t offset, uint64_t bytes, assert(!(bs->open_flags & BDRV_O_INACTIVE)); assert((bs->open_flags & BDRV_O_NO_IO) == 0); assert(!(flags & ~BDRV_REQ_MASK)); + assert(!((flags & BDRV_REQ_NO_WAIT) && !(flags & BDRV_REQ_SERIALISING))); if (flags & BDRV_REQ_SERIALISING) { - waited = bdrv_mark_request_serialising(req, bdrv_get_cluster_size(bs)); - /* - * For a misaligned request we should have already waited earlier, - * because we come after bdrv_padding_rmw_read which must be called - * with the request already marked as serialising. - */ - assert(!waited || - (req->offset == req->overlap_offset && - req->bytes == req->overlap_bytes)); + QEMU_LOCK_GUARD(&bs->reqs_lock); + + tracked_request_set_serialising(req, bdrv_get_cluster_size(bs)); + + if ((flags & BDRV_REQ_NO_WAIT) && bdrv_find_conflicting_request(req)) { + return -EBUSY; + } + + bdrv_wait_serialising_requests_locked(req); } else { bdrv_wait_serialising_requests(req); } @@ -2013,7 +2035,7 @@ static int coroutine_fn bdrv_co_do_zero_pwritev(BdrvChild *child, padding = bdrv_init_padding(bs, offset, bytes, &pad); if (padding) { - bdrv_mark_request_serialising(req, align); + bdrv_make_request_serialising(req, align); bdrv_padding_rmw_read(child, req, &pad, true); @@ -2127,7 +2149,7 @@ int coroutine_fn bdrv_co_pwritev_part(BdrvChild *child, } if (bdrv_pad_request(bs, &qiov, &qiov_offset, &offset, &bytes, &pad)) { - bdrv_mark_request_serialising(&req, align); + bdrv_make_request_serialising(&req, align); bdrv_padding_rmw_read(child, &req, &pad, false); } @@ -3248,7 +3270,7 @@ int coroutine_fn bdrv_co_truncate(BdrvChild *child, int64_t offset, bool exact, * new area, we need to make sure that no write requests are made to it * concurrently or they might be overwritten by preallocation. */ if (new_bytes) { - bdrv_mark_request_serialising(&req, 1); + bdrv_make_request_serialising(&req, 1); } if (bs->read_only) { error_setg(errp, "Image is read-only"); |