dm_task_deferred_remove is not supported by all distributions, due to
out-dated versions of devicemapper. However, in the case where the
devicemapper library was updated without rebuilding Docker (which can
happen in some distributions) then we should attempt to dynamically load
the relevant object rather than try to link to it.
This can only be done if Docker was built dynamically, for obvious
reasons.
In order to avoid having issues arise when dlsym(3) was unnecessary,
gate the whole dlsym(3) logic behind a buildflag that we disable by
default (libdm_dlsym_deferred_remove).
Signed-off-by: Aleksa Sarai <asarai@suse.de>
1. devmapper_wrapper_{,no_}deferred_remove.go:
Comments about LibraryDeferredRemovalSupport were very totally
misleading to me. This thing has nothing to do with either static
or dynamic linking (but with build tags). Fix the comment accordingly.
2. devmapper.go:
Reveal the source of those magic device* constants.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
Deferred reove functionality was added to library later. So in old version
of library it did not report deferred_remove field.
Create a new function which also gets deferred_remove field and it will be
called only on newer version of library.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
A lot of time device mapper devices leak across mount namespace which docker
does not know about and when docker tries to deactivate/delete device,
operation fails as device is open in some mount namespace.
Create a mechanism where one can defer the device deactivation/deletion
so that docker operation does not fail and device automatically goes
away when last reference to it is dropped.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
