{"id":1307017,"url":"http://patchwork.ozlabs.org/api/patches/1307017/?format=json","web_url":"http://patchwork.ozlabs.org/project/qemu-devel/patch/402a16641f750c1069e0926c454f1da7b2eca10b.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":"<402a16641f750c1069e0926c454f1da7b2eca10b.1591801197.git.berto@igalia.com>","list_archive_url":null,"date":"2020-06-10T15:03:01","name":"[v8,23/34] qcow2: Add subcluster support to discard_in_l2_slice()","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"892821a52f95da7b1d34b566135e7595abf4c8f3","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/402a16641f750c1069e0926c454f1da7b2eca10b.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/1307017/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/1307017/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":"Two things need to be taken into account here:\n\n1) With full_discard == true the L2 entry must be cleared completely.\n This also includes the L2 bitmap if the image has extended L2\n entries.\n\n2) With full_discard == false we have to make the discarded cluster\n read back as zeroes. With normal L2 entries this is done with the\n QCOW_OFLAG_ZERO bit, whereas with extended L2 entries this is done\n with the individual 'all zeroes' bits for each subcluster.\n\n Note however that QCOW_OFLAG_ZERO is not supported in v2 qcow2\n images so, if there is a backing file, discard cannot guarantee\n that the image will read back as zeroes. If this is important for\n the caller it should forbid it as qcow2_co_pdiscard() does (see\n 80f5c01183 for more details).\n\nSigned-off-by: Alberto Garcia \nReviewed-by: Eric Blake \n---\n block/qcow2-cluster.c | 52 +++++++++++++++++++------------------------\n 1 file changed, 23 insertions(+), 29 deletions(-)","diff":"diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c\nindex 4e59bbd545..edfc8ea91c 100644\n--- a/block/qcow2-cluster.c\n+++ b/block/qcow2-cluster.c\n@@ -1847,11 +1847,17 @@ static int discard_in_l2_slice(BlockDriverState *bs, uint64_t offset,\n assert(nb_clusters <= INT_MAX);\n \n for (i = 0; i < nb_clusters; i++) {\n- uint64_t old_l2_entry;\n-\n- old_l2_entry = get_l2_entry(s, l2_slice, l2_index + i);\n+ uint64_t old_l2_entry = get_l2_entry(s, l2_slice, l2_index + i);\n+ uint64_t old_l2_bitmap = get_l2_bitmap(s, l2_slice, l2_index + i);\n+ uint64_t new_l2_entry = old_l2_entry;\n+ uint64_t new_l2_bitmap = old_l2_bitmap;\n+ QCow2ClusterType cluster_type =\n+ qcow2_get_cluster_type(bs, old_l2_entry);\n \n /*\n+ * If full_discard is true, the cluster should not read back as zeroes,\n+ * but rather fall through to the backing file.\n+ *\n * If full_discard is false, make sure that a discarded area reads back\n * as zeroes for v3 images (we cannot do it for v2 without actually\n * writing a zero-filled buffer). We can skip the operation if the\n@@ -1860,40 +1866,28 @@ static int discard_in_l2_slice(BlockDriverState *bs, uint64_t offset,\n *\n * TODO We might want to use bdrv_block_status(bs) here, but we're\n * holding s->lock, so that doesn't work today.\n- *\n- * If full_discard is true, the sector should not read back as zeroes,\n- * but rather fall through to the backing file.\n */\n- switch (qcow2_get_cluster_type(bs, old_l2_entry)) {\n- case QCOW2_CLUSTER_UNALLOCATED:\n- if (full_discard || !bs->backing) {\n- continue;\n+ if (full_discard) {\n+ new_l2_entry = new_l2_bitmap = 0;\n+ } else if (bs->backing || qcow2_cluster_is_allocated(cluster_type)) {\n+ if (has_subclusters(s)) {\n+ new_l2_entry = 0;\n+ new_l2_bitmap = QCOW_L2_BITMAP_ALL_ZEROES;\n+ } else {\n+ new_l2_entry = s->qcow_version >= 3 ? QCOW_OFLAG_ZERO : 0;\n }\n- break;\n+ }\n \n- case QCOW2_CLUSTER_ZERO_PLAIN:\n- if (!full_discard) {\n- continue;\n- }\n- break;\n-\n- case QCOW2_CLUSTER_ZERO_ALLOC:\n- case QCOW2_CLUSTER_NORMAL:\n- case QCOW2_CLUSTER_COMPRESSED:\n- break;\n-\n- default:\n- abort();\n+ if (old_l2_entry == new_l2_entry && old_l2_bitmap == new_l2_bitmap) {\n+ continue;\n }\n \n /* First remove L2 entries */\n qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice);\n- if (!full_discard && s->qcow_version >= 3) {\n- set_l2_entry(s, l2_slice, l2_index + i, QCOW_OFLAG_ZERO);\n- } else {\n- set_l2_entry(s, l2_slice, l2_index + i, 0);\n+ set_l2_entry(s, l2_slice, l2_index + i, new_l2_entry);\n+ if (has_subclusters(s)) {\n+ set_l2_bitmap(s, l2_slice, l2_index + i, new_l2_bitmap);\n }\n-\n /* Then decrease the refcount */\n qcow2_free_any_clusters(bs, old_l2_entry, 1, type);\n }\n","prefixes":["v8","23/34"]}