K 10
svn:author
V 3
kib
K 8
svn:date
V 27
2016-06-13T03:42:46.259126Z
K 7
svn:log
V 989
Fix inconsistent locking of the swap pager named objects list.

Right now, all modifications of the list are locked by sw_alloc_mtx.
But initial lookup of the object by the handle in swap_pager_alloc()
is not protected by sw_alloc_mtx, which means that
vm_pager_object_lookup() could follow freed pointer.

Create a new named swap object with the OBJT_SWAP type, instead
of OBJT_DEFAULT.  With this change, swp_pager_meta_build() never need
to upgrade named OBJT_DEFAULT to OBJT_SWAP (in the other place, we do
not forbid for client code to create named OBJT_DEFAULT objects at
all).

That change allows to remove sw_alloc_mtx and make the list locked by
sw_alloc_sx lock.  Update swap_pager_copy() to new locking mode.

Create helper swap_pager_alloc_init() to consolidate named and
anonymous swap objects creation, while a caller ensures that the
neccesary locks are held around the helper.

Reviewed by:	alc
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks
Approved by:	re (hrs)

END