The idea is that ALLOCATE requests may overlap with other requests. Reuse the existing block layer infrastructure for serialising requests. Use the following approach: - mark ALLOCATE serialising, so subsequent requests to the area wait - ALLOCATE request itself must never wait if another request is in flight already. Return EAGAIN, let the caller reconsider.
Signed-off-by: Anton Nefedov <anton.nefe...@virtuozzo.com> --- block/io.c | 32 +++++++++++++++++++++++++------- 1 file changed, 25 insertions(+), 7 deletions(-) diff --git a/block/io.c b/block/io.c index c4f2a07..5d74603 100644 --- a/block/io.c +++ b/block/io.c @@ -599,12 +599,13 @@ void bdrv_dec_in_flight(BlockDriverState *bs) bdrv_wakeup(bs); } -static bool coroutine_fn wait_serialising_requests(BdrvTrackedRequest *self) +static bool coroutine_fn find_or_wait_serialising_requests( + BdrvTrackedRequest *self, bool wait) { BlockDriverState *bs = self->bs; BdrvTrackedRequest *req; bool retry; - bool waited = false; + bool found = false; if (!atomic_read(&bs->serialising_in_flight)) { return false; @@ -630,11 +631,14 @@ static bool coroutine_fn wait_serialising_requests(BdrvTrackedRequest *self) * 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) { + found = true; + if (!wait) { + break; + } self->waiting_for = req; qemu_co_queue_wait(&req->wait_queue, &bs->reqs_lock); self->waiting_for = NULL; retry = true; - waited = true; break; } } @@ -642,7 +646,12 @@ static bool coroutine_fn wait_serialising_requests(BdrvTrackedRequest *self) qemu_co_mutex_unlock(&bs->reqs_lock); } while (retry); - return waited; + return found; +} + +static bool coroutine_fn wait_serialising_requests(BdrvTrackedRequest *self) +{ + return find_or_wait_serialising_requests(self, true); } static int bdrv_check_byte_request(BlockDriverState *bs, int64_t offset, @@ -1474,7 +1483,7 @@ static int coroutine_fn bdrv_aligned_pwritev(BdrvChild *child, { BlockDriverState *bs = child->bs; BlockDriver *drv = bs->drv; - bool waited; + bool found; int ret; int64_t end_sector = DIV_ROUND_UP(offset + bytes, BDRV_SECTOR_SIZE); @@ -1498,8 +1507,13 @@ static int coroutine_fn bdrv_aligned_pwritev(BdrvChild *child, max_transfer = QEMU_ALIGN_DOWN(MIN_NON_ZERO(bs->bl.max_transfer, INT_MAX), align); - waited = wait_serialising_requests(req); - assert(!waited || !req->serialising); + found = find_or_wait_serialising_requests(req, + !(flags & BDRV_REQ_ALLOCATE)); + if (found && (flags & BDRV_REQ_ALLOCATE)) { + return -EAGAIN; + } + + assert(!found || !req->serialising); assert(req->overlap_offset <= offset); assert(offset + bytes <= req->overlap_offset + req->overlap_bytes); assert(child->perm & BLK_PERM_WRITE); @@ -1624,6 +1638,10 @@ static int coroutine_fn bdrv_co_do_zero_pwritev(BdrvChild *child, bytes -= zero_bytes; } + if (flags & BDRV_REQ_ALLOCATE) { + mark_request_serialising(req, align); + } + assert(!bytes || (offset & (align - 1)) == 0); if (bytes >= align) { /* Write the aligned part in the middle. */ -- 2.7.4