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authorStefan Hajnoczi <stefanha@linux.vnet.ibm.com>2011-11-17 13:40:29 +0000
committerKevin Wolf <kwolf@redhat.com>2011-12-05 14:51:38 +0100
commitf4658285f99473367dbbc34ce6970ec4637c2388 (patch)
tree7cc84f22cc93a3fe458c6d483a09d60de064bf71
parent53fec9d3fd3d3a4ded4b92dfa843436bf71380f1 (diff)
downloadqemu-arm-f4658285f99473367dbbc34ce6970ec4637c2388.tar.gz
block: wait for overlapping requests
When copy-on-read is enabled it is necessary to wait for overlapping requests before issuing new requests. This prevents races between the copy-on-read and a write request. Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
-rw-r--r--block.c35
1 files changed, 35 insertions, 0 deletions
diff --git a/block.c b/block.c
index 9b3cb75646..1b3c809ed4 100644
--- a/block.c
+++ b/block.c
@@ -1099,6 +1099,7 @@ struct BdrvTrackedRequest {
int nb_sectors;
bool is_write;
QLIST_ENTRY(BdrvTrackedRequest) list;
+ CoQueue wait_queue; /* coroutines blocked on this request */
};
/**
@@ -1109,6 +1110,7 @@ struct BdrvTrackedRequest {
static void tracked_request_end(BdrvTrackedRequest *req)
{
QLIST_REMOVE(req, list);
+ qemu_co_queue_restart_all(&req->wait_queue);
}
/**
@@ -1126,9 +1128,34 @@ static void tracked_request_begin(BdrvTrackedRequest *req,
.is_write = is_write,
};
+ qemu_co_queue_init(&req->wait_queue);
+
QLIST_INSERT_HEAD(&bs->tracked_requests, req, list);
}
+static bool tracked_request_overlaps(BdrvTrackedRequest *req,
+ int64_t sector_num, int nb_sectors) {
+ return false; /* not yet implemented */
+}
+
+static void coroutine_fn wait_for_overlapping_requests(BlockDriverState *bs,
+ int64_t sector_num, int nb_sectors)
+{
+ BdrvTrackedRequest *req;
+ bool retry;
+
+ do {
+ retry = false;
+ QLIST_FOREACH(req, &bs->tracked_requests, list) {
+ if (tracked_request_overlaps(req, sector_num, nb_sectors)) {
+ qemu_co_queue_wait(&req->wait_queue);
+ retry = true;
+ break;
+ }
+ }
+ } while (retry);
+}
+
/*
* Return values:
* 0 - success
@@ -1423,6 +1450,10 @@ static int coroutine_fn bdrv_co_do_readv(BlockDriverState *bs,
bdrv_io_limits_intercept(bs, false, nb_sectors);
}
+ if (bs->copy_on_read) {
+ wait_for_overlapping_requests(bs, sector_num, nb_sectors);
+ }
+
tracked_request_begin(&req, bs, sector_num, nb_sectors, false);
ret = drv->bdrv_co_readv(bs, sector_num, nb_sectors, qiov);
tracked_request_end(&req);
@@ -1462,6 +1493,10 @@ static int coroutine_fn bdrv_co_do_writev(BlockDriverState *bs,
bdrv_io_limits_intercept(bs, true, nb_sectors);
}
+ if (bs->copy_on_read) {
+ wait_for_overlapping_requests(bs, sector_num, nb_sectors);
+ }
+
tracked_request_begin(&req, bs, sector_num, nb_sectors, true);
ret = drv->bdrv_co_writev(bs, sector_num, nb_sectors, qiov);