From patchwork Mon Sep 4 15:09:58 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jean-Louis Dupond X-Patchwork-Id: 13374084 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id BAD7DC83F2C for ; Mon, 4 Sep 2023 15:11:38 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qdBDd-00066p-Ci; Mon, 04 Sep 2023 11:10:25 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qdBDa-00064r-D1 for qemu-devel@nongnu.org; Mon, 04 Sep 2023 11:10:23 -0400 Received: from apollo.dupie.be ([51.159.20.238]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qdBDX-0001eC-12 for qemu-devel@nongnu.org; Mon, 04 Sep 2023 11:10:22 -0400 Received: from localhost.localdomain (unknown [IPv6:2a02:a03f:eaf7:ff01:ecd9:958e:7098:f62b]) by apollo.dupie.be (Postfix) with ESMTPSA id B81841520C05; Mon, 4 Sep 2023 17:10:11 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=dupond.be; s=dkim; t=1693840211; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=qoob9A43H9kclnpQjtk3rWXPMAq1urfAR7Gk6RM0p0c=; b=IaFz/98bjExOprOa+IqE2DBplXYm1tEAhuEQB1eNsh+I+PJKDnU+Z+Zz75e3G6F3bC1Gnd aGd4vFRRka0yZouAG1K7IRrJGldAHQJIchFqfQVu6naBFJsJ0xdjmkeWHqIvQz2CMVmi5u Jk3SLp2NibYSYfpXAWVfLOF7wGAN51B9KCfTxdViQH4zpsh+AxECW5DI5f/7PReCMtQHCA J7b3B7N8bTf0MZlQgQ2N13Q3YtvwlfgENP5mH4Kv7A4mOhjiDKrxO8FpYPQsZKQYVBCsgT HFE9yiet7VIEOBxgPyvuH0tGoV8kWiVzeoPf7LDH3L4BJosyqCt41ITFzOlLVg== From: Jean-Louis Dupond To: qemu-devel@nongnu.org, kwolf@redhat.com, hreitz@redhat.com Cc: Jean-Louis Dupond Subject: [PATCH] qcow2: keep reference on zeroize with discard-no-unref enabled Date: Mon, 4 Sep 2023 17:09:58 +0200 Message-ID: <20230904150958.823365-1-jean-louis@dupond.be> X-Mailer: git-send-email 2.42.0 MIME-Version: 1.0 Received-SPF: pass client-ip=51.159.20.238; envelope-from=jean-louis@dupond.be; helo=apollo.dupie.be 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, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org When the discard-no-unref flag is enabled, we keep the reference for normal discard requests. But when a discard is executed on a snapshot/qcow2 image with backing, the discards are saved as zero clusters in the snapshot image. When committing the snapshot to the backing file, not discard_in_l2_slice is called but zero_in_l2_slice. Which did not had any logic to keep the reference when discard-no-unref is enabled. Therefor we add logic in the zero_in_l2_slice call to keep the reference on commit. Next to that we also revert some logic from 42a2890a and just call qcow2_free_any_cluster. As this will just decrease the refcount but not remove the reference itself. And it will also send the discard further to the lower layer. Fixes: https://gitlab.com/qemu-project/qemu/-/issues/1621 Signed-off-by: Jean-Louis Dupond --- block/qcow2-cluster.c | 18 +++++++----------- 1 file changed, 7 insertions(+), 11 deletions(-) diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c index f4f6cd6ad0..48532ca3c2 100644 --- a/block/qcow2-cluster.c +++ b/block/qcow2-cluster.c @@ -1975,16 +1975,7 @@ static int discard_in_l2_slice(BlockDriverState *bs, uint64_t offset, if (has_subclusters(s)) { set_l2_bitmap(s, l2_slice, l2_index + i, new_l2_bitmap); } - if (!keep_reference) { - /* Then decrease the refcount */ - qcow2_free_any_cluster(bs, old_l2_entry, type); - } else if (s->discard_passthrough[type] && - (cluster_type == QCOW2_CLUSTER_NORMAL || - cluster_type == QCOW2_CLUSTER_ZERO_ALLOC)) { - /* If we keep the reference, pass on the discard still */ - bdrv_pdiscard(s->data_file, old_l2_entry & L2E_OFFSET_MASK, - s->cluster_size); - } + qcow2_free_any_cluster(bs, old_l2_entry, type); } qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); @@ -2062,9 +2053,14 @@ zero_in_l2_slice(BlockDriverState *bs, uint64_t offset, QCow2ClusterType type = qcow2_get_cluster_type(bs, old_l2_entry); bool unmap = (type == QCOW2_CLUSTER_COMPRESSED) || ((flags & BDRV_REQ_MAY_UNMAP) && qcow2_cluster_is_allocated(type)); - uint64_t new_l2_entry = unmap ? 0 : old_l2_entry; + uint64_t new_l2_entry = old_l2_entry; uint64_t new_l2_bitmap = old_l2_bitmap; + if (unmap && + !(s->discard_no_unref && type != QCOW2_CLUSTER_COMPRESSED)) { + new_l2_entry = 0; + } + if (has_subclusters(s)) { new_l2_bitmap = QCOW_L2_BITMAP_ALL_ZEROES; } else {