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[Qemu-devel] [PATCH v2 6/8] block: request overlap detection
From: |
Stefan Hajnoczi |
Subject: |
[Qemu-devel] [PATCH v2 6/8] block: request overlap detection |
Date: |
Thu, 17 Nov 2011 13:40:30 +0000 |
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 <address@hidden>
---
block.c | 40 ++++++++++++++++++++++++++++++++++++++--
1 files changed, 38 insertions(+), 2 deletions(-)
diff --git a/block.c b/block.c
index da7aaa2..0eef122 100644
--- a/block.c
+++ b/block.c
@@ -1133,21 +1133,57 @@ static void tracked_request_begin(BdrvTrackedRequest
*req,
QLIST_INSERT_HEAD(&bs->tracked_requests, req, list);
}
+/**
+ * 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 = QEMU_ALIGN_DOWN(sector_num, c);
+ *cluster_nb_sectors = QEMU_ALIGN_UP(sector_num - *cluster_sector_num +
+ nb_sectors, 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;
--
1.7.7.1
- [Qemu-devel] [PATCH v2 0/8] block: generic copy-on-read, Stefan Hajnoczi, 2011/11/17
- [Qemu-devel] [PATCH v2 8/8] block: add -drive copy-on-read=on|off, Stefan Hajnoczi, 2011/11/17
- [Qemu-devel] [PATCH v2 3/8] block: add request tracking, Stefan Hajnoczi, 2011/11/17
- [Qemu-devel] [PATCH v2 2/8] coroutine: add qemu_co_queue_restart_all(), Stefan Hajnoczi, 2011/11/17
- [Qemu-devel] [PATCH v2 4/8] block: add bdrv_set_copy_on_read(), Stefan Hajnoczi, 2011/11/17
- [Qemu-devel] [PATCH v2 5/8] block: wait for overlapping requests, Stefan Hajnoczi, 2011/11/17