[Qemu-devel] [PATCH v3 00/27] block: Lock images when opening

[Fam Zheng <famz@redhat.com>]

v3: Highlight is handling of image locks during close(3) and bdrv_reopen(). A
    number of new patches are added consequently. Per patch change logs are:

    [01/27] block: Add BDRV_O_NO_LOCK
            Add Denis's rev-by.

    [03/27] blockdev: Add and parse "lock-image" option for block devices
            Add as root BDS option too.

    [04/27] block: Introduce image file locking
            Treat -ENOTSUP the same as empty .bdrv_lockf.

    [05/27] block: Add bdrv_image_locked
            New.

    [06/27] block: Make bdrv_reopen_{commit,abort} private functions
    [07/27] block: Handle image locking during reopen
            New. Handle reopen. [Laszlo]

    [08/27] osdep: Add qemu_lock_fd and qemu_unlock_fd
    [09/27] osdep: Introduce qemu_dup
    [10/27] raw-posix: Use qemu_dup
    [11/27] raw-posix: Implement .bdrv_lockf
            New. Handle close. [Daniel]

    [12/27] gluster: Implement .bdrv_lockf
            Add Niels' rev-by.

    [13/27] qemu-io: Add "-L" option for BDRV_O_NO_LOCK
            Update argument documentation. [Denis]

    [18/27] mirror: Disable image locking on target backing chain
            New. Target image is not locked.

    [19/27] qemu-iotests: 140: Disable image lock for qemu-io access
    [20/27] qemu-iotests: 046: Move version detection out from verify_io
    [21/27] qemu-iotests: Wait for QEMU processes before checking image in 091
    [22/27] qemu-iotests: 030: Disable image lock when checking test image
    [23/27] iotests: 087: Disable image lock in cases where file is shared
    [24/27] iotests: Disable image locking in 085
    [25/27] tests: Use null-co:// instead of /dev/null
            New. Several updates of testing to avoid image locking voilation.

    [27/27] qemu-iotests: Add test case 153 for image locking
            Add a number of new combinations.

Too many troubles have been caused by two processes writing to the same image
unexpectedly. This series introduces automatical image locking into QEMU to
avoid such tragedy. With this, the user won't be able to open the image from
two processes (e.g. using qemu-img when the image is attached to the guest).

Underneath is the fcntl syscall that locks the local file, similar to what is
already used in libvirt virtlockd. The difference is that libvirt locks byte 0,
we lock byte 1.  Read only openings are mapped to shared locks.

The alternative locking API, flock(2), doesn't provide byte range locking and
is also forwarded to fcntl on Linux NFS mount points, so we'd end up
conflicting with virtlockd. Thus it is not used.

Gluster locking is also implemented wrapping glfs_posix_lock. The patch is
lightly tested.

All other drivers that don't implement .bdrv_lockf are always permissive and do
not check.


Fam Zheng (27):
  block: Add BDRV_O_NO_LOCK
  qapi: Add lock-image in blockdev-add options
  blockdev: Add and parse "lock-image" option for block devices
  block: Introduce image file locking
  block: Add bdrv_image_locked
  block: Make bdrv_reopen_{commit,abort} private functions
  block: Handle image locking during reopen
  osdep: Add qemu_lock_fd and qemu_unlock_fd
  osdep: Introduce qemu_dup
  raw-posix: Use qemu_dup
  raw-posix: Implement .bdrv_lockf
  gluster: Implement .bdrv_lockf
  qemu-io: Add "-L" option for BDRV_O_NO_LOCK
  qemu-img: Add "-L" option to sub commands
  qemu-img: Update documentation of "-L" option
  qemu-nbd: Add "--no-lock/-L" option
  block: Don't lock drive-backup target image in none mode
  mirror: Disable image locking on target backing chain
  qemu-iotests: 140: Disable image lock for qemu-io access
  qemu-iotests: 046: Move version detection out from verify_io
  qemu-iotests: Wait for QEMU processes before checking image in 091
  qemu-iotests: 030: Disable image lock when checking test image
  iotests: 087: Disable image lock in cases where file is shared
  iotests: Disable image locking in 085
  tests: Use null-co:// instead of /dev/null
  block: Turn on image locking by default
  qemu-iotests: Add test case 153 for image locking

 block.c                    |  69 +++++++++++-
 block/gluster.c            |  31 ++++++
 block/raw-posix.c          |  32 ++++--
 blockdev.c                 |  23 ++++
 include/block/block.h      |   6 +-
 include/block/block_int.h  |  12 ++
 include/qemu/osdep.h       |   3 +
 qapi/block-core.json       |   6 +-
 qemu-img-cmds.hx           |  44 ++++----
 qemu-img.c                 |  90 ++++++++++++---
 qemu-img.texi              |   3 +
 qemu-io.c                  |  24 +++-
 qemu-nbd.c                 |   7 +-
 qemu-nbd.texi              |   2 +
 tests/drive_del-test.c     |   2 +-
 tests/nvme-test.c          |   2 +-
 tests/qemu-iotests/030     |   2 +-
 tests/qemu-iotests/046     |  22 ++--
 tests/qemu-iotests/085     |   3 +-
 tests/qemu-iotests/087     |   6 +
 tests/qemu-iotests/091     |   3 +
 tests/qemu-iotests/091.out |   1 +
 tests/qemu-iotests/140     |   2 +-
 tests/qemu-iotests/153     | 191 ++++++++++++++++++++++++++++++++
 tests/qemu-iotests/153.out | 266 +++++++++++++++++++++++++++++++++++++++++++++
 tests/qemu-iotests/group   |   1 +
 tests/usb-hcd-uhci-test.c  |   2 +-
 tests/usb-hcd-xhci-test.c  |   2 +-
 tests/virtio-blk-test.c    |   2 +-
 tests/virtio-scsi-test.c   |   4 +-
 util/osdep.c               | 215 +++++++++++++++++++++++++++++++++---
 31 files changed, 986 insertions(+), 92 deletions(-)
 create mode 100755 tests/qemu-iotests/153
 create mode 100644 tests/qemu-iotests/153.out

-- 
2.8.0