From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:46594) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RXZNf-0001Iy-0D for qemu-devel@nongnu.org; Mon, 05 Dec 2011 09:19:01 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1RXZNY-0000LY-W9 for qemu-devel@nongnu.org; Mon, 05 Dec 2011 09:18:54 -0500 Received: from mx1.redhat.com ([209.132.183.28]:56603) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RXZNY-0000LR-9m for qemu-devel@nongnu.org; Mon, 05 Dec 2011 09:18:48 -0500 From: Kevin Wolf Date: Mon, 5 Dec 2011 15:21:10 +0100 Message-Id: <1323094878-7967-34-git-send-email-kwolf@redhat.com> In-Reply-To: <1323094878-7967-1-git-send-email-kwolf@redhat.com> References: <1323094878-7967-1-git-send-email-kwolf@redhat.com> Subject: [Qemu-devel] [PATCH 33/41] block: wait for overlapping requests List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: anthony@codemonkey.ws Cc: kwolf@redhat.com, qemu-devel@nongnu.org From: Stefan Hajnoczi 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 Signed-off-by: Kevin Wolf --- block.c | 35 +++++++++++++++++++++++++++++++++++ 1 files changed, 35 insertions(+), 0 deletions(-) diff --git a/block.c b/block.c index 9b3cb75..1b3c809 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); -- 1.7.6.4