Merge remote-tracking branch 'remotes/maxreitz/tags/pull-block-2021-03-30' into staging

Block patches for 6.0-rc1:
- Mark the qcow2 cache clean timer as external to fix record/replay
- Fix the mirror filter node's permissions so that an external process
  cannot grab an image while it is used as the mirror source
- Add documentation about FUSE exports to the storage daemon
- When creating a qcow2 image with the data-file-raw option, all
  metadata structures should be preallocated
- iotest fixes

# gpg: Signature made Tue 30 Mar 2021 13:38:40 BST
# gpg:                using RSA key 91BEB60A30DB3E8857D11829F407DB0061D5CF40
# gpg:                issuer "mreitz@redhat.com"
# gpg: Good signature from "Max Reitz <mreitz@redhat.com>" [full]
# Primary key fingerprint: 91BE B60A 30DB 3E88 57D1  1829 F407 DB00 61D5 CF40

* remotes/maxreitz/tags/pull-block-2021-03-30:
  iotests/244: Test preallocation for data-file-raw
  qcow2: Force preallocation with data-file-raw
  qsd: Document FUSE exports
  block/mirror: Fix mirror_top's permissions
  iotests/046: Filter request length
  qcow2: use external virtual timers
  iotests/116: Fix reference output
  iotests: fix 051.out expected output after error text touchups
  iotests: Fix typo in iotest 051

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

1 files changed, 19 insertions, 0 deletions

diff --git a/docs/tools/qemu-storage-daemon.rst b/docs/tools/qemu-storage-daemon.rst
index 086493e..3ec4bdd 100644
--- a/docs/tools/qemu-storage-daemon.rst
+++ b/docs/tools/qemu-storage-daemon.rst
@@ -74,6 +74,7 @@ Standard options:
 .. option:: --export [type=]nbd,id=<id>,node-name=<node-name>[,name=<export-name>][,writable=on|off][,bitmap=<name>]
   --export [type=]vhost-user-blk,id=<id>,node-name=<node-name>,addr.type=unix,addr.path=<socket-path>[,writable=on|off][,logical-block-size=<block-size>][,num-queues=<num-queues>]
   --export [type=]vhost-user-blk,id=<id>,node-name=<node-name>,addr.type=fd,addr.str=<fd>[,writable=on|off][,logical-block-size=<block-size>][,num-queues=<num-queues>]
+  --export [type=]fuse,id=<id>,node-name=<node-name>,mountpoint=<file>[,growable=on|off][,writable=on|off]
 
   is a block export definition. ``node-name`` is the block node that should be
   exported. ``writable`` determines whether or not the export allows write
@@ -92,6 +93,16 @@ Standard options:
   ``logical-block-size`` sets the logical block size in bytes (the default is
   512). ``num-queues`` sets the number of virtqueues (the default is 1).
 
+  The ``fuse`` export type takes a mount point, which must be a regular file,
+  on which to export the given block node. That file will not be changed, it
+  will just appear to have the block node's content while the export is active
+  (very much like mounting a filesystem on a directory does not change what the
+  directory contains, it only shows a different content while the filesystem is
+  mounted). Consequently, applications that have opened the given file before
+  the export became active will continue to see its original content. If
+  ``growable`` is set, writes after the end of the exported file will grow the
+  block node to fit.
+
 .. option:: --monitor MONITORDEF
 
   is a QMP monitor definition. See the :manpage:`qemu(1)` manual page for
@@ -196,6 +207,14 @@ domain socket ``vhost-user-blk.sock``::
       --blockdev driver=qcow2,node-name=qcow2,file=file \
       --export type=vhost-user-blk,id=export,addr.type=unix,addr.path=vhost-user-blk.sock,node-name=qcow2
 
+Export a qcow2 image file ``disk.qcow2`` via FUSE on itself, so the disk image
+file will then appear as a raw image::
+
+  $ qemu-storage-daemon \
+      --blockdev driver=file,node-name=file,filename=disk.qcow2 \
+      --blockdev driver=qcow2,node-name=qcow2,file=file \
+      --export type=fuse,id=export,node-name=qcow2,mountpoint=disk.qcow2,writable=on
+
 See also
 --------