Merge remote-tracking branch 'remotes/maxreitz/tags/pull-block-2020-12-18' into staging

Block patches:
- New block filter: preallocate (which, on writes beyond an image file's
  end, allocates big chunks of data so that such post-EOF writes will
  occur less frequently)
- write-zeroes and block-status support for Quorum
- Implementation of truncate for the nvme block driver similarly to the
  existing implementations for host block devices and iscsi devices
- Block layer refactoring: Drop the tighten_restrictions concept in the
  block permission functions
- iotest fixes

# gpg: Signature made Fri 18 Dec 2020 14:45:30 GMT
# 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-2020-12-18: (30 commits)
  iotests: Fix _send_qemu_cmd with bash 5.1
  iotests/102: Pass $QEMU_HANDLE to _send_qemu_cmd
  block/nvme: Implement fake truncate() coroutine
  quorum: Implement bdrv_co_pwrite_zeroes()
  quorum: Implement bdrv_co_block_status()
  scripts/simplebench: add bench_prealloc.py
  simplebench/results_to_text: make executable
  simplebench/results_to_text: add difference line to the table
  simplebench/results_to_text: improve view of the table
  simplebench: move results_to_text() into separate file
  simplebench: rename ascii() to results_to_text()
  scripts/simplebench: use standard deviation for +- error
  scripts/simplebench: support iops
  scripts/simplebench: fix grammar: s/successed/succeeded/
  iotests: add 298 to test new preallocate filter driver
  iotests.py: execute_setup_common(): add required_fmts argument
  iotests: qemu_io_silent: support --image-opts
  qemu-io: add preallocate mode parameter for truncate command
  block: introduce preallocate filter
  block: bdrv_check_perm(): process children anyway
  ...

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

1 files changed, 26 insertions, 0 deletions

diff --git a/docs/system/qemu-block-drivers.rst.inc b/docs/system/qemu-block-drivers.rst.inc
index b052a6d14e..60a064b232 100644
--- a/docs/system/qemu-block-drivers.rst.inc
+++ b/docs/system/qemu-block-drivers.rst.inc
@@ -952,3 +952,29 @@ on host and see if there are locks held by the QEMU process on the image file.
 More than one byte could be locked by the QEMU instance, each byte of which
 reflects a particular permission that is acquired or protected by the running
 block driver.
+
+Filter drivers
+~~~~~~~~~~~~~~
+
+QEMU supports several filter drivers, which don't store any data, but perform
+some additional tasks, hooking io requests.
+
+.. program:: filter-drivers
+.. option:: preallocate
+
+  The preallocate filter driver is intended to be inserted between format
+  and protocol nodes and preallocates some additional space
+  (expanding the protocol file) when writing past the file’s end. This can be
+  useful for file-systems with slow allocation.
+
+  Supported options:
+
+  .. program:: preallocate
+  .. option:: prealloc-align
+
+    On preallocation, align the file length to this value (in bytes), default 1M.
+
+  .. program:: preallocate
+  .. option:: prealloc-size
+
+    How much to preallocate (in bytes), default 128M.