{"id":817422,"url":"http://patchwork.ozlabs.org/api/patches/817422/?format=json","web_url":"http://patchwork.ozlabs.org/project/qemu-devel/patch/20170922093926.9723-3-pbutsykin@virtuozzo.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":"<20170922093926.9723-3-pbutsykin@virtuozzo.com>","list_archive_url":null,"date":"2017-09-22T09:39:26","name":"[v2,2/2] qcow2: truncate the tail of the image file after shrinking the image","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"37765d5ed79b00d8a1b1330c51158167bf5bfe0b","submitter":{"id":67271,"url":"http://patchwork.ozlabs.org/api/people/67271/?format=json","name":"Pavel Butsykin","email":"pbutsykin@virtuozzo.com"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/qemu-devel/patch/20170922093926.9723-3-pbutsykin@virtuozzo.com/mbox/","series":[{"id":4588,"url":"http://patchwork.ozlabs.org/api/series/4588/?format=json","web_url":"http://patchwork.ozlabs.org/project/qemu-devel/list/?series=4588","date":"2017-09-22T09:39:25","name":"Truncate the tail of the image file in qcow2 shrinking","version":2,"mbox":"http://patchwork.ozlabs.org/series/4588/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/817422/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/817422/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\tspf=pass (mailfrom) smtp.mailfrom=nongnu.org\n\t(client-ip=2001:4830:134:3::11; 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SFP:1102; SCL:1; SRVR:VI1PR0802MB2559;\n\tH:pavelb-Z68P-DS3.sw.ru; FPR:; SPF:None; PTR:InfoNoRecords; A:1;\n\tMX:1; LANG:en; ","Received-SPF":"None (protection.outlook.com: virtuozzo.com does not designate\n\tpermitted sender hosts)","SpamDiagnosticOutput":"1:99","SpamDiagnosticMetadata":"NSPM","X-OriginatorOrg":"virtuozzo.com","X-MS-Exchange-CrossTenant-OriginalArrivalTime":"22 Sep 2017 09:39:54.9261\n\t(UTC)","X-MS-Exchange-CrossTenant-FromEntityHeader":"Hosted","X-MS-Exchange-CrossTenant-Id":"0bc7f26d-0264-416e-a6fc-8352af79c58f","X-MS-Exchange-Transport-CrossTenantHeadersStamped":"VI1PR0802MB2559","X-detected-operating-system":"by eggs.gnu.org: Windows 7 or 8 [fuzzy]","X-Received-From":"40.107.0.133","Subject":"[Qemu-devel] [PATCH v2 2/2] qcow2: truncate the tail of the image\n\tfile after shrinking the image","X-BeenThere":"qemu-devel@nongnu.org","X-Mailman-Version":"2.1.21","Precedence":"list","List-Id":"","List-Unsubscribe":",\n\t","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n\t","Cc":"kwolf@redhat.com, pbutsykin@virtuozzo.com, mreitz@redhat.com,\n\tden@openvz.org, jsnow@redhat.com","Errors-To":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org","Sender":"\"Qemu-devel\"\n\t"},"content":"Now after shrinking the image, at the end of the image file, there might be a\ntail that probably will never be used. So we can find the last used cluster and\ncut the tail.\n\nSigned-off-by: Pavel Butsykin \n---\n block/qcow2-refcount.c | 22 ++++++++++++++++++++++\n block/qcow2.c | 23 +++++++++++++++++++++++\n block/qcow2.h | 1 +\n 3 files changed, 46 insertions(+)","diff":"diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c\nindex 88d5a3f1ad..aa3fd6cf17 100644\n--- a/block/qcow2-refcount.c\n+++ b/block/qcow2-refcount.c\n@@ -3181,3 +3181,25 @@ out:\n g_free(reftable_tmp);\n return ret;\n }\n+\n+int64_t qcow2_get_last_cluster(BlockDriverState *bs, int64_t size)\n+{\n+ BDRVQcow2State *s = bs->opaque;\n+ int64_t i;\n+\n+ for (i = size_to_clusters(s, size) - 1; i >= 0; i--) {\n+ uint64_t refcount;\n+ int ret = qcow2_get_refcount(bs, i, &refcount);\n+ if (ret < 0) {\n+ fprintf(stderr, \"Can't get refcount for cluster %\" PRId64 \": %s\\n\",\n+ i, strerror(-ret));\n+ return ret;\n+ }\n+ if (refcount > 0) {\n+ return i;\n+ }\n+ }\n+ qcow2_signal_corruption(bs, true, -1, -1,\n+ \"There are no references in the refcount table.\");\n+ return -EIO;\n+}\ndiff --git a/block/qcow2.c b/block/qcow2.c\nindex 8a4311d338..8dfb5393a7 100644\n--- a/block/qcow2.c\n+++ b/block/qcow2.c\n@@ -3106,6 +3106,7 @@ static int qcow2_truncate(BlockDriverState *bs, int64_t offset,\n new_l1_size = size_to_l1(s, offset);\n \n if (offset < old_length) {\n+ int64_t last_cluster, old_file_size;\n if (prealloc != PREALLOC_MODE_OFF) {\n error_setg(errp,\n \"Preallocation can't be used for shrinking an image\");\n@@ -3134,6 +3135,28 @@ static int qcow2_truncate(BlockDriverState *bs, int64_t offset,\n \"Failed to discard unused refblocks\");\n return ret;\n }\n+\n+ old_file_size = bdrv_getlength(bs->file->bs);\n+ if (old_file_size < 0) {\n+ error_setg_errno(errp, -old_file_size,\n+ \"Failed to inquire current file length\");\n+ return old_file_size;\n+ }\n+ last_cluster = qcow2_get_last_cluster(bs, old_file_size);\n+ if (last_cluster < 0) {\n+ error_setg_errno(errp, -last_cluster,\n+ \"Failed to find the last cluster\");\n+ return last_cluster;\n+ }\n+ if ((last_cluster + 1) * s->cluster_size < old_file_size) {\n+ ret = bdrv_truncate(bs->file, (last_cluster + 1) * s->cluster_size,\n+ PREALLOC_MODE_OFF, NULL);\n+ if (ret < 0) {\n+ error_setg_errno(errp, -ret,\n+ \"Failed to truncate the tail of the image\");\n+ return ret;\n+ }\n+ }\n } else {\n ret = qcow2_grow_l1_table(bs, new_l1_size, true);\n if (ret < 0) {\ndiff --git a/block/qcow2.h b/block/qcow2.h\nindex 5a289a81e2..782a206ecb 100644\n--- a/block/qcow2.h\n+++ b/block/qcow2.h\n@@ -597,6 +597,7 @@ int qcow2_change_refcount_order(BlockDriverState *bs, int refcount_order,\n BlockDriverAmendStatusCB *status_cb,\n void *cb_opaque, Error **errp);\n int qcow2_shrink_reftable(BlockDriverState *bs);\n+int64_t qcow2_get_last_cluster(BlockDriverState *bs, int64_t size);\n \n /* qcow2-cluster.c functions */\n int qcow2_grow_l1_table(BlockDriverState *bs, uint64_t min_size,\n","prefixes":["v2","2/2"]}