Xen devel - Mar 2009 - [PATCH 0/4] Various blktap related patches (xen part)

The following patch series is the xen repository part of some blktap
related patches that accumulated during SLES 11 development. A qemu-xen
part will follow once these are checked in, so the dependencies are met.

The main point is restoring the possibility to use qemu-dm as a backend
for blktap devices (and mid-term letting tapdisk die with its duplicated
code), but at least the error handling addresses general concerns.

As an overview, we have the following patches:

1) blktapctrl: Select backend by prefix
2) blktap: Export disk type constants for ioemu
3) blktapctrl: Fix too early close of pipes
4) blktap: Move error signaling to blktapctrl

Kevin

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This patch adds support for specifying the backend (tapdisk or ioemu)
to blktapctrl. Images can be specified e.g. as tap:tapdisk:aio,
tap:ioemu:qcow2 or tap:vmdk. When omitting the backend, a default is
chosen based on the image type (currently always tapdisk because ioemu
as a backend is broken until a follow-up patch series against qemu-xen
is applied)

Signed-off-by: Kevin Wolf <kwolf@suse.de>


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Currently all disk types that are supported are defined in a header file
private to blktapctrl and tapdisk. When restoring ioemu as a backend for
blktap these constants are needed by ioemu, so move them to a more
public header file.

Signed-off-by: Kevin Wolf <kwolf@suse.de>


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Connections to ioemu have single_handler set, so they are closed as
soon as all images of a certain type are closed. This is wrong with
ioemu: All images that belong to the same domain are handled by the
same backend process (usually qemu-dm, but also tapdisk-ioemu for
domains without device model), regardless of the image type.

This patch checks for the same-domain condition for ioemu connections.

Signed-off-by: Kevin Wolf <kwolf@suse.de>


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Until now the udev script for blktap devices needs to decide if to
signal success or failure to xend. As this script runs completely
independent of blktapctrl and tapdisk/ioemu which do the real work,
the udev script can''t even theoretically know if tapdisk is happy.

This patch removes the udev script and replaces its checks by new
ones in libblktap.

Signed-off-by: Kevin Wolf <kwolf@suse.de>


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