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[Qemu-devel] [PATCH 34/41] block: request overlap detection
From: |
Kevin Wolf |
Subject: |
[Qemu-devel] [PATCH 34/41] block: request overlap detection |
Date: |
Mon, 5 Dec 2011 15:21:11 +0100 |
From: Stefan Hajnoczi <address@hidden>
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>
Signed-off-by: Kevin Wolf <address@hidden>
---
block.c | 45 +++++++++++++++++++++++++++++++++++++++++++--
1 files changed, 43 insertions(+), 2 deletions(-)
diff --git a/block.c b/block.c
index 1b3c809..ca0e8ec 100644
--- a/block.c
+++ b/block.c
@@ -1133,21 +1133,62 @@ 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. 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.
+ */
+ 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;
--
1.7.6.4
- [Qemu-devel] [PATCH 25/41] vdi: convert to .bdrv_co_is_allocated(), (continued)
- [Qemu-devel] [PATCH 25/41] vdi: convert to .bdrv_co_is_allocated(), Kevin Wolf, 2011/12/05
- [Qemu-devel] [PATCH 29/41] qemu-common: add QEMU_ALIGN_DOWN() and QEMU_ALIGN_UP() macros, Kevin Wolf, 2011/12/05
- [Qemu-devel] [PATCH 31/41] block: add request tracking, Kevin Wolf, 2011/12/05
- [Qemu-devel] [PATCH 30/41] coroutine: add qemu_co_queue_restart_all(), Kevin Wolf, 2011/12/05
- [Qemu-devel] [PATCH 28/41] block: add bdrv_co_is_allocated() interface, Kevin Wolf, 2011/12/05
- [Qemu-devel] [PATCH 32/41] block: add interface to toggle copy-on-read, Kevin Wolf, 2011/12/05
- [Qemu-devel] [PATCH 39/41] block: implement bdrv_co_is_allocated() boundary cases, Kevin Wolf, 2011/12/05
- [Qemu-devel] [PATCH 37/41] cow: use bdrv_co_is_allocated(), Kevin Wolf, 2011/12/05
- [Qemu-devel] [PATCH 35/41] block: core copy-on-read logic, Kevin Wolf, 2011/12/05
- [Qemu-devel] [PATCH 36/41] block: add -drive copy-on-read=on|off, Kevin Wolf, 2011/12/05
- [Qemu-devel] [PATCH 34/41] block: request overlap detection,
Kevin Wolf <=
- [Qemu-devel] [PATCH 40/41] block: wait_for_overlapping_requests() deadlock detection, Kevin Wolf, 2011/12/05
- [Qemu-devel] [PATCH 41/41] block: convert qemu_aio_flush() calls to bdrv_drain_all(), Kevin Wolf, 2011/12/05
- [Qemu-devel] [PATCH 33/41] block: wait for overlapping requests, Kevin Wolf, 2011/12/05
- [Qemu-devel] [PATCH 38/41] dma-helpers: Add trace events, Kevin Wolf, 2011/12/05