diff options
author | Stefan Hajnoczi <stefanha@linux.vnet.ibm.com> | 2011-11-17 13:40:29 +0000 |
---|---|---|
committer | Kevin Wolf <kwolf@redhat.com> | 2011-12-05 14:51:38 +0100 |
commit | f4658285f99473367dbbc34ce6970ec4637c2388 (patch) | |
tree | 7cc84f22cc93a3fe458c6d483a09d60de064bf71 | |
parent | 53fec9d3fd3d3a4ded4b92dfa843436bf71380f1 (diff) |
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.c | 35 |
1 files changed, 35 insertions, 0 deletions
@@ -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); |