Merge remote-tracking branch 'remotes/hreitz-gitlab/tags/pull-block-2022-02-01' into staging

Block patches:
- Add support to the iotests to test qcow2's zstd compression mode
- Fix post-migration block node permissions
- iotests fixes (051 and mirror-ready-cancel-error)
- Remove an outdated comment

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# gpg:                issuer "hreitz@redhat.com"
# gpg: Good signature from "Hanna Reitz <hreitz@redhat.com>" [marginal]
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# Primary key fingerprint: CB62 D7A0 EE38 29E4 5F00  4D34 A1FA 40D0 9801 9CDF

* remotes/hreitz-gitlab/tags/pull-block-2022-02-01: (24 commits)
  block.h: remove outdated comment
  iotests/migration-permissions: New test
  block-backend: Retain permissions after migration
  iotests: declare lack of support for compresion_type in IMGOPTS
  iotest 214: explicit compression type
  iotests 60: more accurate set dirty bit in qcow2 header
  iotests: bash tests: filter compression type
  iotest 39: use _qcow2_dump_header
  iotests: massive use _qcow2_dump_header
  iotests/common.rc: introduce _qcow2_dump_header helper
  qcow2: simple case support for downgrading of qcow2 images with zstd
  iotest 302: use img_info_log() helper
  iotests.py: filter compression type out
  iotests.py: filter out successful output of qemu-img create
  iotest 065: explicit compression type
  iotest 303: explicit compression type
  iotests.py: rewrite default luks support in qemu_img
  iotests: drop qemu_img_verbose() helper
  iotests.py: qemu_img*("create"): support IMGOPTS='compression_type=zstd'
  iotests: specify some unsupported_imgopts for python iotests
  ...

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

2 files changed, 67 insertions, 2 deletions

diff --git a/block/block-backend.c b/block/block-backend.c
index 23e7271..4ff6b4d 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -190,6 +190,7 @@ static void blk_root_activate(BdrvChild *child, Error **errp)
 {
     BlockBackend *blk = child->opaque;
     Error *local_err = NULL;
+    uint64_t saved_shared_perm;
 
     if (!blk->disable_perm) {
         return;
@@ -197,12 +198,22 @@ static void blk_root_activate(BdrvChild *child, Error **errp)
 
     blk->disable_perm = false;
 
+    /*
+     * blk->shared_perm contains the permissions we want to share once
+     * migration is really completely done.  For now, we need to share
+     * all; but we also need to retain blk->shared_perm, which is
+     * overwritten by a successful blk_set_perm() call.  Save it and
+     * restore it below.
+     */
+    saved_shared_perm = blk->shared_perm;
+
     blk_set_perm(blk, blk->perm, BLK_PERM_ALL, &local_err);
     if (local_err) {
         error_propagate(errp, local_err);
         blk->disable_perm = true;
         return;
     }
+    blk->shared_perm = saved_shared_perm;
 
     if (runstate_check(RUN_STATE_INMIGRATE)) {
         /* Activation can happen when migration process is still active, for
diff --git a/block/qcow2.c b/block/qcow2.c
index d509016..c8115e1 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -5279,6 +5279,38 @@ static int qcow2_load_vmstate(BlockDriverState *bs, QEMUIOVector *qiov,
     return bs->drv->bdrv_co_preadv_part(bs, offset, qiov->size, qiov, 0, 0);
 }
 
+static int qcow2_has_compressed_clusters(BlockDriverState *bs)
+{
+    int64_t offset = 0;
+    int64_t bytes = bdrv_getlength(bs);
+
+    if (bytes < 0) {
+        return bytes;
+    }
+
+    while (bytes != 0) {
+        int ret;
+        QCow2SubclusterType type;
+        unsigned int cur_bytes = MIN(INT_MAX, bytes);
+        uint64_t host_offset;
+
+        ret = qcow2_get_host_offset(bs, offset, &cur_bytes, &host_offset,
+                                    &type);
+        if (ret < 0) {
+            return ret;
+        }
+
+        if (type == QCOW2_SUBCLUSTER_COMPRESSED) {
+            return 1;
+        }
+
+        offset += cur_bytes;
+        bytes -= cur_bytes;
+    }
+
+    return 0;
+}
+
 /*
  * Downgrades an image's version. To achieve this, any incompatible features
  * have to be removed.
@@ -5336,9 +5368,10 @@ static int qcow2_downgrade(BlockDriverState *bs, int target_version,
      * the first place; if that happens nonetheless, returning -ENOTSUP is the
      * best thing to do anyway */
 
-    if (s->incompatible_features) {
+    if (s->incompatible_features & ~QCOW2_INCOMPAT_COMPRESSION) {
         error_setg(errp, "Cannot downgrade an image with incompatible features "
-                   "%#" PRIx64 " set", s->incompatible_features);
+                   "0x%" PRIx64 " set",
+                   s->incompatible_features & ~QCOW2_INCOMPAT_COMPRESSION);
         return -ENOTSUP;
     }
 
@@ -5356,6 +5389,27 @@ static int qcow2_downgrade(BlockDriverState *bs, int target_version,
         return ret;
     }
 
+    if (s->incompatible_features & QCOW2_INCOMPAT_COMPRESSION) {
+        ret = qcow2_has_compressed_clusters(bs);
+        if (ret < 0) {
+            error_setg(errp, "Failed to check block status");
+            return -EINVAL;
+        }
+        if (ret) {
+            error_setg(errp, "Cannot downgrade an image with zstd compression "
+                       "type and existing compressed clusters");
+            return -ENOTSUP;
+        }
+        /*
+         * No compressed clusters for now, so just chose default zlib
+         * compression.
+         */
+        s->incompatible_features &= ~QCOW2_INCOMPAT_COMPRESSION;
+        s->compression_type = QCOW2_COMPRESSION_TYPE_ZLIB;
+    }
+
+    assert(s->incompatible_features == 0);
+
     s->qcow_version = target_version;
     ret = qcow2_update_header(bs);
     if (ret < 0) {