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[130.117.225.111]) by mx.google.com with ESMTPS id ffacd0b85a97d-48c724be20fsi9771037f8f.482.2026.10.08.03.04.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 08 Oct 2026 03:04:54 -0700 (PDT) Received-SPF: pass (google.com: domain of alexander.ivanov@virtuozzo.com designates 130.117.225.111 as permitted sender) client-ip=130.117.225.111; Authentication-Results: mx.google.com; dkim=pass header.i=@virtuozzo.com header.s=relay header.b=lPxHfoXd; spf=pass (google.com: domain of alexander.ivanov@virtuozzo.com designates 130.117.225.111 as permitted sender) smtp.mailfrom=alexander.ivanov@virtuozzo.com; dmarc=pass (p=QUARANTINE sp=QUARANTINE dis=NONE) header.from=virtuozzo.com DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=virtuozzo.com; s=relay; h=MIME-Version:Message-ID:Date:Subject:From: Content-Type; bh=QCwtjReL9B55hq5zy+HU0zCI9E2ByuCa67rXiD7PzuM=; b=lPxHfoXd0+45 61fRVl2Z0/2kCFTeS5fqgv7BIH8m+rieIqVltSMDCm4kv45/GmC8zKgBjWOEA0sHUAmJPAi/XX2SM qvOkBrsTReUH5Ofrc2hAstzjUwCYnb6DO09/DZ4T99RLokp9Pe7b0Xl2nvhTPF3IdlA4Rg0tEQENK aEO7SFSFBMwmWZ0f0a2y9nEynkc3vA3gaMP+kO+GaaOqv9o8yedkdrpAN2HfmoerZF9cw1H9uzIHb P3IjGqE+pXeU+g7JoBzj1mKTiqk2Pa1e9y8w3wUQFcP1Ywyls14sN4RRhl4RIiCwRe/0CjFgk49y8 iHXIsvrwIdK4d98/vv/gbQ==; Received: from ch-vpn.virtuozzo.com ([130.117.225.6] helo=sky) by relay.virtuozzo.com with esmtps (TLS1.3) tls TLS_AES_256_GCM_SHA384 (Exim 4.96) (envelope-from ) id 1xEkwM-00Aash-2W; Thu, 08 Oct 2026 12:04:52 +0200 From: Alexander Ivanov To: den@openvz.org Date: Thu, 8 Oct 2026 12:04:49 +0200 Message-ID: <20261008100449.550882-4-alexander.ivanov@virtuozzo.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261008100449.550882-1-alexander.ivanov@virtuozzo.com> References: <20261008100449.550882-1-alexander.ivanov@virtuozzo.com> MIME-Version: 1.0 X-OZ-Fwd: true Cc: devel@openvz.org Subject: [Devel] [PATCH hci-8.1 v3 3/3] dm-qcow2: truncate unused tail of image on suspend X-BeenThere: devel@openvz.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: OpenVZ development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: devel-bounces@openvz.org Errors-To: devel-bounces@openvz.org On postsuspend we truncate the image file only down to file_preallocated_area_start, i.e. we drop preallocations only. Clusters at the end of the file freed by discard (refcount dropped to zero) are never given back, so the file size never shrinks. Add qcow2_calc_used_end(), which scans refcount blocks backward from file_preallocated_area_start and returns the end of the last cluster with non-zero refcount. Refcount ranges with no allocated refblock are skipped at once. Metadata pages are taken from md cache or read synchronously. This is called on suspended device after md writeback, so R1 and R2 can't change under us. Truncate the file to the used end. Skip the scan if md writeback failed, as refcounts on disk are stale then, and fall back to the old behaviour on scan error. https://virtuozzo.atlassian.net/browse/VSTOR-148171 Feature: dm-qcow2: block device over QCOW2 files driver Signed-off-by: Alexander Ivanov --- drivers/md/dm-qcow2-map.c | 56 ++++++++++++++++++++++++++++++++++++ drivers/md/dm-qcow2-target.c | 12 +++++++- drivers/md/dm-qcow2.h | 1 + 3 files changed, 68 insertions(+), 1 deletion(-) diff --git a/drivers/md/dm-qcow2-map.c b/drivers/md/dm-qcow2-map.c index 78ee7cf5e881..65ee6ae144bf 100644 --- a/drivers/md/dm-qcow2-map.c +++ b/drivers/md/dm-qcow2-map.c @@ -2208,6 +2208,62 @@ int qcow2_truncate_safe(struct file *file, loff_t new_len) return do_ftruncate(file, new_len, 0); } +/* + * Returns the end of the last cluster, which is used according + * to refcount table, clamped to file_preallocated_area_start since + * the last cluster may be partial. Clusters freed by discard may + * leave the tail of file unused. Everything at or above + * file_preallocated_area_start is unused by construction, so the scan + * starts below it. This must be called on suspended device after md + * writeback, so nobody changes R1 and R2. + */ +loff_t qcow2_calc_used_end(struct qcow2 *qcow2) +{ + u32 clu_size = qcow2->clu_size; + struct qcow2_map_item r1, r2; + struct md_page *r1_md = NULL; + loff_t pos; + s32 i; + int ret; + + pos = round_down(qcow2->file_preallocated_area_start - 1, clu_size); + while (pos >= 0) { + if (calc_refcounters_map(qcow2, pos, &r1, &r2) < 0) + return -EIO; + + if (!r1_md || r1_md->id != r1.page_id) { + ret = qcow2_md_page_read_sync(qcow2, r1.page_id, &r1_md); + if (ret) + return ret; + } + r1.md = r1_md; + + ret = calc_r2_page_id(qcow2, &r1, &r2); + if (ret == -ENOENT) { + /* No R2 cluster, so all clusters it covers are unused */ + pos = (loff_t)r1.index * qcow2->refblock_entries * clu_size; + pos -= clu_size; + continue; + } + + if (ret < 0) + return ret; + + ret = qcow2_md_page_read_sync(qcow2, r2.page_id, &r2.md); + if (ret) + return ret; + + for (i = r2.index_in_page; i >= 0; i--, pos -= clu_size) { + /* Last cluster is partial if size isn't cluster-aligned */ + if (get_r2_entry(qcow2, r2.md, i)) + return min_t(loff_t, pos + clu_size, + qcow2->file_preallocated_area_start); + } + } + + return -EIO; +} + static int truncate_prealloc_safe(struct qcow2 *qcow2, loff_t len, const char *func) { loff_t prealloc_len, max_prealloc_len = qcow2->reftable_max_file_size; diff --git a/drivers/md/dm-qcow2-target.c b/drivers/md/dm-qcow2-target.c index b3d5d5e8c7c2..5a72d0f2e9ef 100644 --- a/drivers/md/dm-qcow2-target.c +++ b/drivers/md/dm-qcow2-target.c @@ -1042,11 +1042,21 @@ static void qcow2_truncate_preallocations(struct dm_target *ti) { struct qcow2_target *tgt = to_qcow2_target(ti); struct qcow2 *qcow2 = top_qcow2_protected(ti); - loff_t end = qcow2->file_preallocated_area_start; + loff_t used_end, end = qcow2->file_preallocated_area_start; int ret; if (!(dm_table_get_mode(ti->table) & FMODE_WRITE)) return; + + /* Refcounts on disk are stale after failed md writeback */ + if (!tgt->md_writeback_error) { + used_end = qcow2_calc_used_end(qcow2); + if (used_end < 0) + QC_ERR(ti, "Can't find used end: %pe", ERR_PTR(used_end)); + else + end = used_end; + } + if (end == qcow2->file_size) return; diff --git a/drivers/md/dm-qcow2.h b/drivers/md/dm-qcow2.h index 69d3ae6fca8a..73d3cf175bbf 100644 --- a/drivers/md/dm-qcow2.h +++ b/drivers/md/dm-qcow2.h @@ -411,6 +411,7 @@ void qcow2_ref_dec(struct qcow2_target *tgt, u8 ref_index); int qcow2_inflight_ref_switch(struct qcow2_target *tgt); void qcow2_flush_deferred_activity(struct qcow2_target *tgt, struct qcow2 *qcow2); int qcow2_truncate_safe(struct file *file, loff_t new_len); +loff_t qcow2_calc_used_end(struct qcow2 *qcow2); void qcow2_merge_backward_work(struct work_struct *work); void qcow2_merge_backward_cancel(struct qcow2_target *tgt); -- 2.53.0 _______________________________________________ Devel mailing list Devel@openvz.org https://lists.openvz.org/mailman/listinfo/devel