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Tue, 25 Aug 2020 08:34:06 +0000 (UTC) Received: from localhost (ovpn-113-72.ams2.redhat.com [10.36.113.72]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 801457D939; Tue, 25 Aug 2020 08:34:06 +0000 (UTC) From: Max Reitz To: qemu-block@nongnu.org Subject: [PULL 23/34] qcow2: Add subcluster support to discard_in_l2_slice() Date: Tue, 25 Aug 2020 10:33:00 +0200 Message-Id: <20200825083311.1098442-24-mreitz@redhat.com> In-Reply-To: <20200825083311.1098442-1-mreitz@redhat.com> References: <20200825083311.1098442-1-mreitz@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mreitz@redhat.com X-Mimecast-Spam-Score: 0.001 X-Mimecast-Originator: redhat.com Received-SPF: pass client-ip=207.211.31.81; envelope-from=mreitz@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/08/25 01:36:47 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.956, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , Peter Maydell , qemu-devel@nongnu.org, Max Reitz Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" From: Alberto Garcia Two things need to be taken into account here: 1) With full_discard == true the L2 entry must be cleared completely. This also includes the L2 bitmap if the image has extended L2 entries. 2) With full_discard == false we have to make the discarded cluster read back as zeroes. With normal L2 entries this is done with the QCOW_OFLAG_ZERO bit, whereas with extended L2 entries this is done with the individual 'all zeroes' bits for each subcluster. Note however that QCOW_OFLAG_ZERO is not supported in v2 qcow2 images so, if there is a backing file, discard cannot guarantee that the image will read back as zeroes. If this is important for the caller it should forbid it as qcow2_co_pdiscard() does (see 80f5c01183 for more details). Signed-off-by: Alberto Garcia Reviewed-by: Eric Blake Reviewed-by: Max Reitz Message-Id: <5ef8274e628aa3ab559bfac467abf488534f2b76.1594396418.git.berto@igalia.com> Signed-off-by: Max Reitz --- block/qcow2-cluster.c | 52 +++++++++++++++++++------------------------ 1 file changed, 23 insertions(+), 29 deletions(-) diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c index 5afcd72f5a..a41351aba5 100644 --- a/block/qcow2-cluster.c +++ b/block/qcow2-cluster.c @@ -1848,11 +1848,17 @@ static int discard_in_l2_slice(BlockDriverState *bs, uint64_t offset, assert(nb_clusters <= INT_MAX); for (i = 0; i < nb_clusters; i++) { - uint64_t old_l2_entry; - - old_l2_entry = get_l2_entry(s, l2_slice, l2_index + i); + uint64_t old_l2_entry = get_l2_entry(s, l2_slice, l2_index + i); + uint64_t old_l2_bitmap = get_l2_bitmap(s, l2_slice, l2_index + i); + uint64_t new_l2_entry = old_l2_entry; + uint64_t new_l2_bitmap = old_l2_bitmap; + QCow2ClusterType cluster_type = + qcow2_get_cluster_type(bs, old_l2_entry); /* + * If full_discard is true, the cluster should not read back as zeroes, + * but rather fall through to the backing file. + * * If full_discard is false, make sure that a discarded area reads back * as zeroes for v3 images (we cannot do it for v2 without actually * writing a zero-filled buffer). We can skip the operation if the @@ -1861,40 +1867,28 @@ static int discard_in_l2_slice(BlockDriverState *bs, uint64_t offset, * * TODO We might want to use bdrv_block_status(bs) here, but we're * holding s->lock, so that doesn't work today. - * - * If full_discard is true, the sector should not read back as zeroes, - * but rather fall through to the backing file. */ - switch (qcow2_get_cluster_type(bs, old_l2_entry)) { - case QCOW2_CLUSTER_UNALLOCATED: - if (full_discard || !bs->backing) { - continue; - } - break; - - case QCOW2_CLUSTER_ZERO_PLAIN: - if (!full_discard) { - continue; + if (full_discard) { + new_l2_entry = new_l2_bitmap = 0; + } else if (bs->backing || qcow2_cluster_is_allocated(cluster_type)) { + if (has_subclusters(s)) { + new_l2_entry = 0; + new_l2_bitmap = QCOW_L2_BITMAP_ALL_ZEROES; + } else { + new_l2_entry = s->qcow_version >= 3 ? QCOW_OFLAG_ZERO : 0; } - break; - - case QCOW2_CLUSTER_ZERO_ALLOC: - case QCOW2_CLUSTER_NORMAL: - case QCOW2_CLUSTER_COMPRESSED: - break; + } - default: - abort(); + if (old_l2_entry == new_l2_entry && old_l2_bitmap == new_l2_bitmap) { + continue; } /* First remove L2 entries */ qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice); - if (!full_discard && s->qcow_version >= 3) { - set_l2_entry(s, l2_slice, l2_index + i, QCOW_OFLAG_ZERO); - } else { - set_l2_entry(s, l2_slice, l2_index + i, 0); + set_l2_entry(s, l2_slice, l2_index + i, new_l2_entry); + if (has_subclusters(s)) { + set_l2_bitmap(s, l2_slice, l2_index + i, new_l2_bitmap); } - /* Then decrease the refcount */ qcow2_free_any_clusters(bs, old_l2_entry, 1, type); }