We're about to enable the use of O_DIRECT in the migration code and
due to the alignment restrictions imposed by filesystems we need to
make sure the flag is only used when doing aligned IO.
The migration will do parallel IO to different regions of a file, so
we need to use more than one file descriptor. Those cannot be obtained
by duplicating (dup()) since duplicated file descriptors share the
file status flags, including O_DIRECT. If one migration channel does
unaligned IO while another sets O_DIRECT to do aligned IO, the
filesystem would fail the unaligned operation.
The add-fd QMP command along with the fdset code are specifically
designed to allow the user to pass a set of file descriptors with
different access flags into QEMU to be later fetched by code that
needs to alternate between those flags when doing IO.
Extend the fdset matching function to behave the same with the
O_DIRECT flag.
Signed-off-by: Fabiano Rosas <farosas@suse.de>
We're about to add one more condition to the flags comparison that
requires an ifdef. Move the code into a separate function now to make
it cleaner after the next patch.
Signed-off-by: Fabiano Rosas <farosas@suse.de>
We're currently only removing an fd from the fdset if the VM is
running. This causes a QMP call to "remove-fd" to not actually remove
the fd if the VM happens to be stopped.
While the fd would eventually be removed when monitor_fdset_cleanup()
is called again, the user request should be honored and the fd
actually removed. Calling remove-fd + query-fdset shows a recently
removed fd still present.
The runstate_is_running() check was introduced by commit ebe52b592d
("monitor: Prevent removing fd from set during init"), which by the
shortlog indicates that they were trying to avoid removing an
yet-unduplicated fd too early.
I don't see why an fd explicitly removed with qmp_remove_fd() should
be under runstate_is_running(). I'm assuming this was a mistake when
adding the parenthesis around the expression.
Move the runstate_is_running() check to apply only to the
QLIST_EMPTY(dup_fds) side of the expression and ignore it when
mon_fdset_fd->removed has been explicitly set.
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Currently, the function will simply fail if ancillary fds are not
provided, for ex on unsupported platforms.
This changes the failure from:
{"error": {"class": "GenericError", "desc": "No file descriptor
supplied via SCM_RIGHTS"}}
to:
{"error": {"class": "CommandNotFound", "desc": "The command getfd
has not been found"}}
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
