Merge tag 'for-upstream' of https://repo.or.cz/qemu/kevin into staging

Block layer patches

- Optimise reqs_lock to make multiqueue actually scale
- virtio: Drop out of coroutine context in virtio_load()
- iotests: Fix reference output for some tests after recent changes
- vpc: Avoid dynamic stack allocation
- Code cleanup, improved documentation

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* tag 'for-upstream' of https://repo.or.cz/qemu/kevin:
  virtio: Drop out of coroutine context in virtio_load()
  vmstate: Mark VMStateInfo.get/put() coroutine_mixed_fn
  block: Make more BlockDriver definitions static
  block/meson.build: Restore alphabetical order of files
  block: Remove unnecessary variable in bdrv_block_device_info
  block: Remove bdrv_query_block_node_info
  vmdk: Clean up bdrv_open_child() return value check
  qemu-img: Update documentation for compressed images
  block: Be more verbose in create fallback
  block/iscsi: Document why we use raw malloc()
  qemu-img: omit errno value in error message
  block: change reqs_lock to QemuMutex
  block: minimize bs->reqs_lock section in tracked_request_end()
  iotests: adapt test output for new qemu_cleanup() behavior
  block/vpc: Avoid dynamic stack allocation

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

1 files changed, 17 insertions, 2 deletions

diff --git a/docs/tools/qemu-img.rst b/docs/tools/qemu-img.rst
index 15aeddc6d8..ca5a2773cf 100644
--- a/docs/tools/qemu-img.rst
+++ b/docs/tools/qemu-img.rst
@@ -106,7 +106,11 @@ by the used format or see the format descriptions below for details.
 
 .. option:: -c
 
-  Indicates that target image must be compressed (qcow format only).
+  Indicates that target image must be compressed (qcow/qcow2 and vmdk with
+  streamOptimized subformat only).
+
+  For qcow2, the compression algorithm can be specified with the ``-o
+  compression_type=...`` option (see below).
 
 .. option:: -h
 
@@ -776,7 +780,7 @@ Supported image file formats:
 
   QEMU image format, the most versatile format. Use it to have smaller
   images (useful if your filesystem does not supports holes, for example
-  on Windows), optional AES encryption, zlib based compression and
+  on Windows), optional AES encryption, zlib or zstd based compression and
   support of multiple VM snapshots.
 
   Supported options:
@@ -794,6 +798,17 @@ Supported image file formats:
   ``backing_fmt``
     Image format of the base image
 
+  ``compression_type``
+    This option configures which compression algorithm will be used for
+    compressed clusters on the image. Note that setting this option doesn't yet
+    cause the image to actually receive compressed writes. It is most commonly
+    used with the ``-c`` option of ``qemu-img convert``, but can also be used
+    with the ``compress`` filter driver or backup block jobs with compression
+    enabled.
+
+    Valid values are ``zlib`` and ``zstd``. For images that use
+    ``compat=0.10``, only ``zlib`` compression is available.
+
   ``encryption``
     If this option is set to ``on``, the image is encrypted with
     128-bit AES-CBC.