From 9ffea646c2e25b081bab3b5cf610db8093280aac Mon Sep 17 00:00:00 2001 From: Jeffrey Cody Date: Wed, 21 Mar 2012 21:54:55 +0100 Subject: [PATCH 28/55] block: request overlap detection RH-Author: Jeffrey Cody Message-id: <1f296a89632e9e19657cb9165896af849157b763.1332362400.git.jcody@redhat.com> Patchwork-id: 38878 O-Subject: [RHEL6.3 qemu-kvm PATCH v8 28/54] block: request overlap detection Bugzilla: 582475 RH-Acked-by: Paolo Bonzini RH-Acked-by: Marcelo Tosatti RH-Acked-by: Kevin Wolf From: Stefan Hajnoczi 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 Signed-off-by: Kevin Wolf (cherry picked from commit d83947ac6d2a58fdaf128fbe1b22bc9639e79fe5) Signed-off-by: Stefan Hajnoczi Signed-off-by: Anthony Liguori Signed-off-by: Jeff Cody --- block.c | 45 +++++++++++++++++++++++++++++++++++++++++++-- 1 files changed, 43 insertions(+), 2 deletions(-) Signed-off-by: Michal Novotny --- block.c | 45 +++++++++++++++++++++++++++++++++++++++++++-- 1 files changed, 43 insertions(+), 2 deletions(-) diff --git a/block.c b/block.c index 14d9201..9aefe51 100644 --- a/block.c +++ b/block.c @@ -1138,21 +1138,62 @@ 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; -- 1.7.7.6