[PATCH 00/18] block: Allow exporting BDSs via FUSE

[Max Reitz]

Preamble: This series is based on a combination of my (current) block
branch and “iotests: Minor fixes”.  I’ve pushed it here:

  https://git.xanclic.moe/XanClic/qemu fuse-exports-v1

(The base is on fuse-exports-v1-base.)


Hi,

Ever since I found out that you can mount FUSE filesystems on regular
files (not just directories), I had the idea of adding FUSE block
exports to qemu where you can export block nodes as raw images.  The
best thing is that you’d be able to mount an image on itself, so
whatever format it may be in, qemu lets it appear as a raw image (and
you can then use regular tools like dd on it).

I started with some concept of a qemu-blkfuse daemon (similar to
qemu-nbd), but never sent patches, for two reasons: (1) Performance was
not good, (2) it didn’t seem right, for some reason.

Now Kevin is proposing a storage daemon for multiple export types like
NBD, and he also mentioned FUSE (while knowing of my previous attempts).
Now it does seem right to add FUSE exports to qemu, but only in the form
of some module with a proper QAPI/QMP binding.

Performance is still quite bad, but who cares.  We can always improve
it, if the need arises.


This series does the following:

First, add the FUSE export module (block/fuse.c) that implements the
basic file access functions.  (Note that you need libfuse 3.8.0 or later
for SEEK_HOLE/SEEK_DATA.)

Second, it allows using FUSE exports as a protocol in the iotests and
makes many iotests work with it.  (The file node is exported by a
background qemu instance to $SOCK_DIR.)
Note that I only ran raw and qcow2 on it; I’m sure other formats
currently have some failing tests.

This gives us a lot of coverage for, well, not free (it does take ten
patches), but for cheap; but there are still some more specialized
things we want to test, so third and last, this series adds an iotest
dedicated to FUSE exports.


Final rather important notice: I didn’t really run the iotests with this
yet.  I wanted to, but they appear rather broken on current master,
actually.  I’m not yet sure whether that’s because something in my setup
broke in the last two weeks, or because there’s quite something broken
in master (it does look like there are a couple things broken in master
currently).


Max Reitz (18):
  configure: Detect libfuse
  fuse: Allow exporting BDSs via FUSE
  fuse: Implement standard FUSE operations
  fuse: Add fuse-export-remove
  fuse: Allow growable exports
  fuse: (Partially) implement fallocate()
  fuse: Implement hole detection through lseek
  iotests: Do not needlessly filter _make_test_img
  iotests: Do not pipe _make_test_img
  iotests: Use convert -n in some cases
  iotests: Avoid renaming images
  iotests: Derive image names from $TEST_IMG
  iotests/091: Use _cleanup_qemu instad of "wait"
  iotests: Restrict some Python tests to file
  iotests: Let _make_test_img guess $TEST_IMG_FILE
  iotests: Allow testing FUSE exports
  iotests: Enable fuse for many tests
  iotests/281: Add test for FUSE exports

 block.c                          |   4 +
 block/Makefile.objs              |   3 +
 block/fuse.c                     | 668 +++++++++++++++++++++++++++++++
 configure                        |  68 ++++
 include/block/fuse.h             |  24 ++
 qapi/block.json                  |  42 ++
 tests/qemu-iotests/013           |   9 +-
 tests/qemu-iotests/013.out       |   3 +-
 tests/qemu-iotests/018           |   5 +-
 tests/qemu-iotests/018.out       |   1 +
 tests/qemu-iotests/020           |   2 +-
 tests/qemu-iotests/025           |   2 +-
 tests/qemu-iotests/026           |   2 +-
 tests/qemu-iotests/028           |  16 +-
 tests/qemu-iotests/028.out       |   3 +
 tests/qemu-iotests/031           |   2 +-
 tests/qemu-iotests/034           |   2 +-
 tests/qemu-iotests/036           |   2 +-
 tests/qemu-iotests/037           |   2 +-
 tests/qemu-iotests/038           |   2 +-
 tests/qemu-iotests/039           |   2 +-
 tests/qemu-iotests/046           |   7 +-
 tests/qemu-iotests/046.out       |   2 +-
 tests/qemu-iotests/050           |   2 +-
 tests/qemu-iotests/054           |   2 +-
 tests/qemu-iotests/060           |   2 +-
 tests/qemu-iotests/071           |  21 +-
 tests/qemu-iotests/072           |   5 +-
 tests/qemu-iotests/072.out       |   1 +
 tests/qemu-iotests/079           |   2 +-
 tests/qemu-iotests/080           |   2 +-
 tests/qemu-iotests/089           |   5 +-
 tests/qemu-iotests/089.out       |   1 +
 tests/qemu-iotests/090           |   2 +-
 tests/qemu-iotests/091           |   5 +-
 tests/qemu-iotests/095           |   2 +-
 tests/qemu-iotests/097           |   2 +-
 tests/qemu-iotests/098           |   2 +-
 tests/qemu-iotests/102           |   2 +-
 tests/qemu-iotests/103           |   2 +-
 tests/qemu-iotests/106           |   2 +-
 tests/qemu-iotests/107           |   2 +-
 tests/qemu-iotests/108           |   2 +-
 tests/qemu-iotests/111           |   2 +-
 tests/qemu-iotests/112           |   2 +-
 tests/qemu-iotests/115           |   2 +-
 tests/qemu-iotests/117           |   2 +-
 tests/qemu-iotests/120           |   2 +-
 tests/qemu-iotests/121           |   2 +-
 tests/qemu-iotests/127           |   2 +-
 tests/qemu-iotests/133           |   2 +-
 tests/qemu-iotests/137           |   2 +-
 tests/qemu-iotests/138           |   2 +-
 tests/qemu-iotests/140           |   2 +-
 tests/qemu-iotests/154           |   2 +-
 tests/qemu-iotests/161           |  14 +-
 tests/qemu-iotests/171           |   2 +-
 tests/qemu-iotests/174           |  10 +-
 tests/qemu-iotests/175           |   8 +-
 tests/qemu-iotests/176           |   2 +-
 tests/qemu-iotests/177           |   2 +-
 tests/qemu-iotests/179           |   2 +-
 tests/qemu-iotests/183           |   2 +-
 tests/qemu-iotests/186           |   2 +-
 tests/qemu-iotests/187           |   2 +-
 tests/qemu-iotests/191           |   2 +-
 tests/qemu-iotests/195           |   2 +-
 tests/qemu-iotests/200           |   5 +-
 tests/qemu-iotests/200.out       |   4 +-
 tests/qemu-iotests/204           |   2 +-
 tests/qemu-iotests/206           |   1 +
 tests/qemu-iotests/214           |   2 +-
 tests/qemu-iotests/217           |   2 +-
 tests/qemu-iotests/220           |   2 +-
 tests/qemu-iotests/221           |   2 +-
 tests/qemu-iotests/229           |   5 +-
 tests/qemu-iotests/229.out       |   6 +-
 tests/qemu-iotests/242           |   1 +
 tests/qemu-iotests/247           |   2 +-
 tests/qemu-iotests/249           |   8 +-
 tests/qemu-iotests/250           |   2 +-
 tests/qemu-iotests/252           |   2 +-
 tests/qemu-iotests/265           |   2 +-
 tests/qemu-iotests/268           |   2 +-
 tests/qemu-iotests/272           |   2 +-
 tests/qemu-iotests/273           |   2 +-
 tests/qemu-iotests/279           |   2 +-
 tests/qemu-iotests/281           | 328 +++++++++++++++
 tests/qemu-iotests/281.out       |  92 +++++
 tests/qemu-iotests/check         |   6 +
 tests/qemu-iotests/common.filter |   5 +-
 tests/qemu-iotests/common.rc     | 190 ++++++++-
 tests/qemu-iotests/group         |   1 +
 93 files changed, 1571 insertions(+), 120 deletions(-)
 create mode 100644 block/fuse.c
 create mode 100644 include/block/fuse.h
 create mode 100755 tests/qemu-iotests/281
 create mode 100644 tests/qemu-iotests/281.out

-- 
2.23.0