Detect overlapping requests and remember to align to cluster boundaries
if the image format uses them. This assumes that allocating I/O is
performed in cluster granularity - which is true for qcow2, qed, etc.
Signed-off-by: Stefan Hajnoczi <stefa...@linux.vnet.ibm.com>
---
block.c | 39 +++++++++++++++++++++++++++++++++++++--
1 files changed, 37 insertions(+), 2 deletions(-)
diff --git a/block.c b/block.c
index cc3202c..0c22741 100644
--- a/block.c
+++ b/block.c
@@ -1052,21 +1052,56 @@ static BdrvTrackedRequest
*tracked_request_add(BlockDriverState *bs,
return req;
}
+/**
+ * Round a region to cluster boundaries
+ */
+static void round_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 = (sector_num / c) * c;
+ *cluster_nb_sectors = ((sector_num % c) + nb_sectors + c - 1) / c * c;
+ }
+}
+
static bool tracked_request_overlaps(BdrvTrackedRequest *req,
int64_t sector_num, int nb_sectors) {
- return false; /* not yet implemented */
+ /* aaaa bbbb */
+ if (sector_num >= req->sector_num + req->nb_sectors) {
+ return false;
+ }
+ /* bbbb aaaa */
+ if (req->sector_num >= sector_num + nb_sectors) {
+ return false;
+ }
+ return true;
}
static void coroutine_fn wait_for_overlapping_requests(BlockDriverState *bs,
int64_t sector_num, int nb_sectors)
{
BdrvTrackedRequest *req;
+ int64_t cluster_sector_num;
+ int cluster_nb_sectors;
bool retry;
+ /* If we touch the same cluster it counts as an overlap */
+ round_to_clusters(bs, sector_num, nb_sectors,
+ &cluster_sector_num, &cluster_nb_sectors);
+
do {
retry = false;
QLIST_FOREACH(req, &bs->tracked_requests, list) {
- if (tracked_request_overlaps(req, sector_num, nb_sectors)) {
+ if (tracked_request_overlaps(req, cluster_sector_num,
+ cluster_nb_sectors)) {
qemu_co_queue_wait(&req->wait_queue);
retry = true;
break;
--
1.7.6.3
