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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>
This commit is contained in:
Stefan Hajnoczi 2011-11-17 13:40:29 +00:00 committed by Kevin Wolf
parent 53fec9d3fd
commit f4658285f9
1 changed files with 35 additions and 0 deletions
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35
block.c
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@ -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);