{"id":1307027,"url":"http://patchwork.ozlabs.org/api/patches/1307027/?format=json","web_url":"http://patchwork.ozlabs.org/project/qemu-devel/patch/42651a32704f79337daa357aba4840ec9219b3f2.1591801197.git.berto@igalia.com/","project":{"id":14,"url":"http://patchwork.ozlabs.org/api/projects/14/?format=json","name":"QEMU Development","link_name":"qemu-devel","list_id":"qemu-devel.nongnu.org","list_email":"qemu-devel@nongnu.org","web_url":"","scm_url":"","webscm_url":"","list_archive_url":"","list_archive_url_format":"","commit_url_format":""},"msgid":"<42651a32704f79337daa357aba4840ec9219b3f2.1591801197.git.berto@igalia.com>","list_archive_url":null,"date":"2020-06-10T15:03:05","name":"[v8,27/34] qcow2: Add subcluster support to handle_alloc_space()","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"fd7a8032b4a36393ff8d719ad5970e7b25e216ae","submitter":{"id":65704,"url":"http://patchwork.ozlabs.org/api/people/65704/?format=json","name":"Alberto Garcia","email":"berto@igalia.com"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/qemu-devel/patch/42651a32704f79337daa357aba4840ec9219b3f2.1591801197.git.berto@igalia.com/mbox/","series":[{"id":182563,"url":"http://patchwork.ozlabs.org/api/series/182563/?format=json","web_url":"http://patchwork.ozlabs.org/project/qemu-devel/list/?series=182563","date":"2020-06-10T15:02:49","name":"Add subcluster allocation to qcow2","version":8,"mbox":"http://patchwork.ozlabs.org/series/182563/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/1307027/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/1307027/checks/","tags":{},"related":[],"headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@bilbo.ozlabs.org","Authentication-Results":["ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org\n (client-ip=209.51.188.17; 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envelope-from=berto@igalia.com;\n helo=fanzine.igalia.com","X-detected-operating-system":"by eggs.gnu.org: First seen = 2020/06/10 11:03:39","X-ACL-Warn":"Detected OS = Linux 2.2.x-3.x (no timestamps) [generic] [fuzzy]","X-Spam_score_int":"-20","X-Spam_score":"-2.1","X-Spam_bar":"--","X-Spam_report":"(-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1,\n DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_NONE=0.001,\n SPF_PASS=-0.001 autolearn=_AUTOLEARN","X-Spam_action":"no action","X-BeenThere":"qemu-devel@nongnu.org","X-Mailman-Version":"2.1.23","Precedence":"list","List-Id":"","List-Unsubscribe":",\n ","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n ","Cc":"Kevin Wolf ,\n Vladimir Sementsov-Ogievskiy ,\n Alberto Garcia , qemu-block@nongnu.org,\n Derek Su , Max Reitz ","Errors-To":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org","Sender":"\"Qemu-devel\"\n "},"content":"The bdrv_co_pwrite_zeroes() call here fills complete clusters with\nzeroes, but it can happen that some subclusters are not part of the\nwrite request or the copy-on-write. This patch makes sure that only\nthe affected subclusters are overwritten.\n\nA potential improvement would be to also fill with zeroes the other\nsubclusters if we can guarantee that we are not overwriting existing\ndata. However this would waste more disk space, so we should first\nevaluate if it's really worth doing.\n\nSigned-off-by: Alberto Garcia \nReviewed-by: Max Reitz \nReviewed-by: Vladimir Sementsov-Ogievskiy \n---\n block/qcow2.c | 9 +++++----\n 1 file changed, 5 insertions(+), 4 deletions(-)","diff":"diff --git a/block/qcow2.c b/block/qcow2.c\nindex a3481cd85b..86258fbc22 100644\n--- a/block/qcow2.c\n+++ b/block/qcow2.c\n@@ -2411,6 +2411,9 @@ static int handle_alloc_space(BlockDriverState *bs, QCowL2Meta *l2meta)\n \n for (m = l2meta; m != NULL; m = m->next) {\n int ret;\n+ uint64_t start_offset = m->alloc_offset + m->cow_start.offset;\n+ unsigned nb_bytes = m->cow_end.offset + m->cow_end.nb_bytes -\n+ m->cow_start.offset;\n \n if (!m->cow_start.nb_bytes && !m->cow_end.nb_bytes) {\n continue;\n@@ -2425,16 +2428,14 @@ static int handle_alloc_space(BlockDriverState *bs, QCowL2Meta *l2meta)\n * efficiently zero out the whole clusters\n */\n \n- ret = qcow2_pre_write_overlap_check(bs, 0, m->alloc_offset,\n- m->nb_clusters * s->cluster_size,\n+ ret = qcow2_pre_write_overlap_check(bs, 0, start_offset, nb_bytes,\n true);\n if (ret < 0) {\n return ret;\n }\n \n BLKDBG_EVENT(bs->file, BLKDBG_CLUSTER_ALLOC_SPACE);\n- ret = bdrv_co_pwrite_zeroes(s->data_file, m->alloc_offset,\n- m->nb_clusters * s->cluster_size,\n+ ret = bdrv_co_pwrite_zeroes(s->data_file, start_offset, nb_bytes,\n BDRV_REQ_NO_FALLBACK);\n if (ret < 0) {\n if (ret != -ENOTSUP && ret != -EAGAIN) {\n","prefixes":["v8","27/34"]}