src/sys/vm/vm_object.c, branch release/6.0.0_cvs

This commit was manufactured by cvs2svn to create tag

2005-11-03T00:35:26+00:00

'RELENG_6_0_0_RELEASE'.

This commit was manufactured to restore the state of the 6.0-RELEASE image.

MFRELENG_6 (by alc) changesets that addresses several race conditions that

2005-10-26T20:22:00+00:00

can cause a kernel compiled with ZERO_COPY_SOCKETS to panic under certain
circumstances:
	sys/kern/uipc_cow.c:	1.24 - 1.26
	sys/vm/vm_object.c:	1.351

Approved by:	re (scottl)

MFC: Don't allow pagedaemon to skip pages while scanning active and

2005-08-12T16:43:27+00:00

     inactive page queues due to the vm object being locked.

Approved by:	re (kensmith)

- We need to inhert the OBJ_NEEDGIANT flag from the original object in

2005-05-04T20:54:16+00:00

   vm_object_split().

Spotted by:	alc

- Add a new object flag "OBJ_NEEDSGIANT". We set this flag if the

2005-05-03T11:11:26+00:00

   underlying vnode requires Giant.
 - In vm_fault only acquire Giant if the underlying object has NEEDSGIANT
   set.
 - In vm_object_shadow inherit the NEEDSGIANT flag from the backing object.

Eliminate (now) unnecessary acquisition and release of the global page

2005-03-30T05:40:02+00:00

queues lock in vm_object_backing_scan().  Updates to the page's PG_BUSY
flag and busy field are synchronized by the containing object's lock.

Testing the page's hold_count and wire_count in vm_object_backing_scan()'s
OBSC_COLLAPSE_NOWAIT case is unnecessary.  There is no reason why the held
or wired pages cannot be migrated to the shadow object.

Reviewed by: tegge

- Don't lock the vnode interlock in vm_object_set_writeable_dirty() if

2005-03-17T12:03:42+00:00

   we've already set the object flags.

Reviewed by:	alc

Update the text of an assertion to reflect changes made in revision 1.148.

2005-01-30T21:29:47+00:00

Submitted by: tegge

Eliminate an unnecessary, temporary increment of the backing object's
reference count in vm_object_qcollapse().  Reviewed by: tegge

- Remove GIANT_REQUIRED where giant is no longer required.

2005-01-24T10:48:29+00:00

 - Use VFS_LOCK_GIANT() rather than directly acquiring giant in places
   where giant is only held because vfs requires it.

Sponsored By:   Isilon Systems, Inc.

Consider three objects, O, BO, and BBO, where BO is O's backing object

2005-01-15T21:12:47+00:00

and BBO is BO's backing object.  Now, suppose that O and BO are being
collapsed.  Furthermore, suppose that BO has been marked dead
(OBJ_DEAD) by vm_object_backing_scan() and that either
vm_object_backing_scan() has been forced to sleep due to encountering
a busy page or vm_object_collapse() has been forced to sleep due to
memory allocation in the swap pager.  If vm_object_deallocate() is
then called on BBO and BO is BBO's only shadow object,
vm_object_deallocate() will collapse BO and BBO.  In doing so, it adds
a necessary temporary reference to BO.  If this collapse also sleeps
and the prior collapse resumes first, the temporary reference will
cause vm_object_collapse to panic with the message "backing_object %p
was somehow re-referenced during collapse!"

Resolve this race by changing vm_object_deallocate() such that it
doesn't collapse BO and BBO if BO is marked dead.  Once O and BO are
collapsed, vm_object_collapse() will attempt to collapse O and BBO.
So, vm_object_deallocate() on BBO need do nothing.

Reported by: Peter Holm on 20050107
URL: http://www.holm.cc/stress/log/cons102.html

In collaboration with: tegge@
Candidate for RELENG_4 and RELENG_5
MFC after: 2 weeks