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From 53db4963174d9f65bd8ba04636ba0adba7615996 Mon Sep 17 00:00:00 2001
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From: Max Reitz <mreitz@redhat.com>
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Date: Tue, 7 Jan 2014 21:57:13 +0100
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Subject: [PATCH 08/14] qcow2: Implement bdrv_amend_options
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RH-Author: Max Reitz <mreitz@redhat.com>
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Message-id: <1389131839-12920-9-git-send-email-mreitz@redhat.com>
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Patchwork-id: 56544
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O-Subject: [RHEL-7.0 qemu-kvm PATCH v2 08/14] qcow2: Implement bdrv_amend_options
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Bugzilla: 1033490
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RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
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RH-Acked-by: Fam Zheng <famz@redhat.com>
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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BZ: 1033490
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Implement bdrv_amend_options for compat, size, backing_file, backing_fmt
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and lazy_refcounts.
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Downgrading images from compat=1.1 to compat=0.10 is achieved through
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handling all incompatible flags accordingly, clearing all compatible and
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autoclear flags and expanding all zero clusters.
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Signed-off-by: Max Reitz <mreitz@redhat.com>
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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(cherry picked from commit 9296b3ed7050cc6e0645fbc3b0aea74406d7eeb2)
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Signed-off-by: Max Reitz <mreitz@redhat.com>
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---
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 block/qcow2.c | 194 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
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 1 file changed, 194 insertions(+)
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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 block/qcow2.c |  194 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
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 1 files changed, 194 insertions(+), 0 deletions(-)
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diff --git a/block/qcow2.c b/block/qcow2.c
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index 0a53a3c..5b28259 100644
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--- a/block/qcow2.c
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+++ b/block/qcow2.c
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@@ -1989,6 +1989,199 @@ static int qcow2_load_vmstate(BlockDriverState *bs, uint8_t *buf,
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     return ret;
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 }
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+/*
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+ * Downgrades an image's version. To achieve this, any incompatible features
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+ * have to be removed.
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+ */
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+static int qcow2_downgrade(BlockDriverState *bs, int target_version)
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+{
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+    BDRVQcowState *s = bs->opaque;
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+    int current_version = s->qcow_version;
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+    int ret;
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+
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+    if (target_version == current_version) {
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+        return 0;
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+    } else if (target_version > current_version) {
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+        return -EINVAL;
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+    } else if (target_version != 2) {
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+        return -EINVAL;
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+    }
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+
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+    if (s->refcount_order != 4) {
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+        /* we would have to convert the image to a refcount_order == 4 image
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+         * here; however, since qemu (at the time of writing this) does not
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+         * support anything different than 4 anyway, there is no point in doing
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+         * so right now; however, we should error out (if qemu supports this in
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+         * the future and this code has not been adapted) */
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+        error_report("qcow2_downgrade: Image refcount orders other than 4 are"
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+                     "currently not supported.");
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+        return -ENOTSUP;
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+    }
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+
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+    /* clear incompatible features */
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+    if (s->incompatible_features & QCOW2_INCOMPAT_DIRTY) {
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+        ret = qcow2_mark_clean(bs);
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+        if (ret < 0) {
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+            return ret;
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+        }
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+    }
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+
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+    /* with QCOW2_INCOMPAT_CORRUPT, it is pretty much impossible to get here in
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+     * the first place; if that happens nonetheless, returning -ENOTSUP is the
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+     * best thing to do anyway */
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+
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+    if (s->incompatible_features) {
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+        return -ENOTSUP;
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+    }
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+
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+    /* since we can ignore compatible features, we can set them to 0 as well */
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+    s->compatible_features = 0;
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+    /* if lazy refcounts have been used, they have already been fixed through
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+     * clearing the dirty flag */
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+
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+    /* clearing autoclear features is trivial */
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+    s->autoclear_features = 0;
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+
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+    ret = qcow2_expand_zero_clusters(bs);
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+    if (ret < 0) {
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+        return ret;
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+    }
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+
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+    s->qcow_version = target_version;
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+    ret = qcow2_update_header(bs);
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+    if (ret < 0) {
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+        s->qcow_version = current_version;
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+        return ret;
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+    }
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+    return 0;
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+}
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+
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+static int qcow2_amend_options(BlockDriverState *bs,
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+                               QEMUOptionParameter *options)
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+{
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+    BDRVQcowState *s = bs->opaque;
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+    int old_version = s->qcow_version, new_version = old_version;
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+    uint64_t new_size = 0;
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+    const char *backing_file = NULL, *backing_format = NULL;
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+    bool lazy_refcounts = s->use_lazy_refcounts;
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+    int ret;
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+    int i;
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+
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+    for (i = 0; options[i].name; i++)
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+    {
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+        if (!options[i].assigned) {
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+            /* only change explicitly defined options */
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+            continue;
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+        }
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+
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+        if (!strcmp(options[i].name, "compat")) {
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+            if (!options[i].value.s) {
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+                /* preserve default */
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+            } else if (!strcmp(options[i].value.s, "0.10")) {
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+                new_version = 2;
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+            } else if (!strcmp(options[i].value.s, "1.1")) {
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+                new_version = 3;
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+            } else {
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+                fprintf(stderr, "Unknown compatibility level %s.\n",
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+                        options[i].value.s);
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+                return -EINVAL;
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+            }
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+        } else if (!strcmp(options[i].name, "preallocation")) {
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+            fprintf(stderr, "Cannot change preallocation mode.\n");
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+            return -ENOTSUP;
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+        } else if (!strcmp(options[i].name, "size")) {
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+            new_size = options[i].value.n;
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+        } else if (!strcmp(options[i].name, "backing_file")) {
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+            backing_file = options[i].value.s;
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+        } else if (!strcmp(options[i].name, "backing_fmt")) {
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+            backing_format = options[i].value.s;
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+        } else if (!strcmp(options[i].name, "encryption")) {
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+            if ((options[i].value.n != !!s->crypt_method)) {
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+                fprintf(stderr, "Changing the encryption flag is not "
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+                        "supported.\n");
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+                return -ENOTSUP;
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+            }
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+        } else if (!strcmp(options[i].name, "cluster_size")) {
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+            if (options[i].value.n != s->cluster_size) {
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+                fprintf(stderr, "Changing the cluster size is not "
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+                        "supported.\n");
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+                return -ENOTSUP;
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+            }
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+        } else if (!strcmp(options[i].name, "lazy_refcounts")) {
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+            lazy_refcounts = options[i].value.n;
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+        } else {
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+            /* if this assertion fails, this probably means a new option was
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+             * added without having it covered here */
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+            assert(false);
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+        }
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+    }
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+
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+    if (new_version != old_version) {
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+        if (new_version > old_version) {
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+            /* Upgrade */
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+            s->qcow_version = new_version;
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+            ret = qcow2_update_header(bs);
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+            if (ret < 0) {
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+                s->qcow_version = old_version;
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+                return ret;
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+            }
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+        } else {
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+            ret = qcow2_downgrade(bs, new_version);
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+            if (ret < 0) {
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+                return ret;
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+            }
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+        }
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+    }
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+
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+    if (backing_file || backing_format) {
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+        ret = qcow2_change_backing_file(bs, backing_file ?: bs->backing_file,
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+                                        backing_format ?: bs->backing_format);
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+        if (ret < 0) {
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+            return ret;
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+        }
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+    }
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+
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+    if (s->use_lazy_refcounts != lazy_refcounts) {
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+        if (lazy_refcounts) {
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+            if (s->qcow_version < 3) {
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+                fprintf(stderr, "Lazy refcounts only supported with compatibility "
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+                        "level 1.1 and above (use compat=1.1 or greater)\n");
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+                return -EINVAL;
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+            }
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+            s->compatible_features |= QCOW2_COMPAT_LAZY_REFCOUNTS;
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+            ret = qcow2_update_header(bs);
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+            if (ret < 0) {
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+                s->compatible_features &= ~QCOW2_COMPAT_LAZY_REFCOUNTS;
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+                return ret;
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+            }
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+            s->use_lazy_refcounts = true;
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+        } else {
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+            /* make image clean first */
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+            ret = qcow2_mark_clean(bs);
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+            if (ret < 0) {
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+                return ret;
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+            }
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+            /* now disallow lazy refcounts */
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+            s->compatible_features &= ~QCOW2_COMPAT_LAZY_REFCOUNTS;
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+            ret = qcow2_update_header(bs);
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+            if (ret < 0) {
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+                s->compatible_features |= QCOW2_COMPAT_LAZY_REFCOUNTS;
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+                return ret;
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+            }
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+            s->use_lazy_refcounts = false;
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+        }
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+    }
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+
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+    if (new_size) {
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+        ret = bdrv_truncate(bs, new_size);
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+        if (ret < 0) {
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+            return ret;
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+        }
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+    }
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+
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+    return 0;
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+}
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+
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 static QEMUOptionParameter qcow2_create_options[] = {
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     {
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         .name = BLOCK_OPT_SIZE,
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@@ -2073,6 +2266,7 @@ static BlockDriver bdrv_qcow2 = {
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     .create_options = qcow2_create_options,
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     .bdrv_check = qcow2_check,
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+    .bdrv_amend_options = qcow2_amend_options,
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 };
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 static void bdrv_qcow2_init(void)
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-- 
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1.7.1
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