tree 0b416dc586098c594d67cc9f966ba905ee168ed6
parent c9d20029f43a08c6362a655c2c5272612186a004
author Kevin Wolf <kwolf@redhat.com> 1466074770 +0200
committer Kevin Wolf <kwolf@redhat.com> 1466083196 +0200

block: Fix snapshot=on with aio=native

snapshot=on creates a temporary overlay that is always opened with
cache=unsafe (the cache mode specified by the user is only for the
actual image file and its children). This means that we must not inherit
the BDRV_O_NATIVE_AIO flag for the temporary overlay because trying to
use Linux AIO with cache=unsafe results in an error.

Reproducer without this patch:

$ x86_64-softmmu/qemu-system-x86_64 -drive file=/tmp/test.qcow2,cache=none,aio=native,snapshot=on
qemu-system-x86_64: -drive file=/tmp/test.qcow2,cache=none,aio=native,snapshot=on: aio=native was
specified, but it requires cache.direct=on, which was not specified.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>