The soft and hard busy mechanism rely on the vm object lock to work.

Unify the 2 concept into a real, minimal, sxlock where the shared
acquisition represent the soft busy and the exclusive acquisition
represent the hard busy.
The old VPO_WANTED mechanism becames the hard-path for this new lock
and it becomes per-page rather than per-object.
The vm_object lock becames an interlock for this functionality:
it can be held in both read or write mode.
However, if the vm_object lock is held in read mode while acquiring
or releasing the busy state, the thread owner cannot make any
assumption on the busy state unless it is also busying it.

Also:
- Add a new flag to directly shared busy pages while vm_page_alloc
  and vm_page_grab are being executed.  This will be very helpful
  once these functions happen under a read object lock.
- Move the swapping sleep into its own per-object flag

The KPI is heavilly changed this is why the version is bumped.
It is very likely that some VM ports users will need to change
their own code.

Sponsored by:	EMC / Isilon storage division
Discussed with:	alc
Reviewed by:	jeff, kib
Tested by:	gavin, bapt (older version)
Tested by:	pho, scottl

1 files changed, 10 insertions, 12 deletions

diff --git a/sys/powerpc/booke/pmap.c b/sys/powerpc/booke/pmap.c
index 9c07d95..b2b958f 100644
--- a/sys/powerpc/booke/pmap.c
+++ b/sys/powerpc/booke/pmap.c
@@ -1563,7 +1563,7 @@ mmu_booke_enter_locked(mmu_t mmu, pmap_t pmap, vm_offset_t va, vm_page_t m,
 		KASSERT((va <= VM_MAXUSER_ADDRESS),
 		    ("mmu_booke_enter_locked: user pmap, non user va"));
 	}
-	if ((m->oflags & (VPO_UNMANAGED | VPO_BUSY)) == 0)
+	if ((m->oflags & VPO_UNMANAGED) == 0 && !vm_page_xbusied(m))
 		VM_OBJECT_ASSERT_LOCKED(m->object);
 
 	PMAP_LOCK_ASSERT(pmap, MA_OWNED);
@@ -1959,13 +1959,12 @@ mmu_booke_remove_write(mmu_t mmu, vm_page_t m)
 	    ("mmu_booke_remove_write: page %p is not managed", m));
 
 	/*
-	 * If the page is not VPO_BUSY, then PGA_WRITEABLE cannot be set by
-	 * another thread while the object is locked.  Thus, if PGA_WRITEABLE
-	 * is clear, no page table entries need updating.
+	 * If the page is not exclusive busied, then PGA_WRITEABLE cannot be
+	 * set by another thread while the object is locked.  Thus,
+	 * if PGA_WRITEABLE is clear, no page table entries need updating.
 	 */
 	VM_OBJECT_ASSERT_WLOCKED(m->object);
-	if ((m->oflags & VPO_BUSY) == 0 &&
-	    (m->aflags & PGA_WRITEABLE) == 0)
+	if (!vm_page_xbusied(m) && (m->aflags & PGA_WRITEABLE) == 0)
 		return;
 	rw_wlock(&pvh_global_lock);
 	TAILQ_FOREACH(pv, &m->md.pv_list, pv_link) {
@@ -2204,13 +2203,12 @@ mmu_booke_is_modified(mmu_t mmu, vm_page_t m)
 	rv = FALSE;
 
 	/*
-	 * If the page is not VPO_BUSY, then PGA_WRITEABLE cannot be
+	 * If the page is not exclusive busied, then PGA_WRITEABLE cannot be
 	 * concurrently set while the object is locked.  Thus, if PGA_WRITEABLE
 	 * is clear, no PTEs can be modified.
 	 */
 	VM_OBJECT_ASSERT_WLOCKED(m->object);
-	if ((m->oflags & VPO_BUSY) == 0 &&
-	    (m->aflags & PGA_WRITEABLE) == 0)
+	if (!vm_page_xbusied(m) && (m->aflags & PGA_WRITEABLE) == 0)
 		return (rv);
 	rw_wlock(&pvh_global_lock);
 	TAILQ_FOREACH(pv, &m->md.pv_list, pv_link) {
@@ -2281,13 +2279,13 @@ mmu_booke_clear_modify(mmu_t mmu, vm_page_t m)
 	KASSERT((m->oflags & VPO_UNMANAGED) == 0,
 	    ("mmu_booke_clear_modify: page %p is not managed", m));
 	VM_OBJECT_ASSERT_WLOCKED(m->object);
-	KASSERT((m->oflags & VPO_BUSY) == 0,
-	    ("mmu_booke_clear_modify: page %p is busy", m));
+	KASSERT(!vm_page_xbusied(m),
+	    ("mmu_booke_clear_modify: page %p is exclusive busied", m));
 
 	/*
 	 * If the page is not PG_AWRITEABLE, then no PTEs can be modified.
 	 * If the object containing the page is locked and the page is not
-	 * VPO_BUSY, then PG_AWRITEABLE cannot be concurrently set.
+	 * exclusive busied, then PG_AWRITEABLE cannot be concurrently set.
 	 */
 	if ((m->aflags & PGA_WRITEABLE) == 0)
 		return;