Split the vm_page flags PG_WRITEABLE and PG_REFERENCED into atomic

flags field. Updates to the atomic flags are performed using the atomic
ops on the containing word, do not require any vm lock to be held, and
are non-blocking. The vm_page_aflag_set(9) and vm_page_aflag_clear(9)
functions are provided to modify afalgs.

Document the changes to flags field to only require the page lock.

Introduce vm_page_reference(9) function to provide a stable KPI and
KBI for filesystems like tmpfs and zfs which need to mark a page as
referenced.

Reviewed by:    alc, attilio
Tested by:      marius, flo (sparc64); andreast (powerpc, powerpc64)
Approved by:	re (bz)

2 files changed, 26 insertions, 26 deletions

diff --git a/sys/powerpc/aim/mmu_oea.c b/sys/powerpc/aim/mmu_oea.c
index 331dbe9..57c35bf 100644
--- a/sys/powerpc/aim/mmu_oea.c
+++ b/sys/powerpc/aim/mmu_oea.c
@@ -1102,7 +1102,7 @@ moea_enter_locked(pmap_t pmap, vm_offset_t va, vm_page_t m, vm_prot_t prot,
 		pte_lo |= PTE_BW;
 		if (pmap_bootstrapped &&
 		    (m->oflags & VPO_UNMANAGED) == 0)
-			vm_page_flag_set(m, PG_WRITEABLE);
+			vm_page_aflag_set(m, PGA_WRITEABLE);
 	} else
 		pte_lo |= PTE_BR;
 
@@ -1255,13 +1255,13 @@ moea_is_modified(mmu_t mmu, vm_page_t m)
 	    ("moea_is_modified: page %p is not managed", m));
 
 	/*
-	 * If the page is not VPO_BUSY, then PG_WRITEABLE cannot be
-	 * concurrently set while the object is locked.  Thus, if PG_WRITEABLE
+	 * If the page is not VPO_BUSY, then PGA_WRITEABLE cannot be
+	 * concurrently set while the object is locked.  Thus, if PGA_WRITEABLE
 	 * is clear, no PTEs can have PTE_CHG set.
 	 */
 	VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
 	if ((m->oflags & VPO_BUSY) == 0 &&
-	    (m->flags & PG_WRITEABLE) == 0)
+	    (m->aflags & PGA_WRITEABLE) == 0)
 		return (FALSE);
 	return (moea_query_bit(m, PTE_CHG));
 }
@@ -1299,11 +1299,11 @@ moea_clear_modify(mmu_t mmu, vm_page_t m)
 	    ("moea_clear_modify: page %p is busy", m));
 
 	/*
-	 * If the page is not PG_WRITEABLE, then no PTEs can have PTE_CHG
+	 * If the page is not PGA_WRITEABLE, then no PTEs can have PTE_CHG
 	 * set.  If the object containing the page is locked and the page is
-	 * not VPO_BUSY, then PG_WRITEABLE cannot be concurrently set.
+	 * not VPO_BUSY, then PGA_WRITEABLE cannot be concurrently set.
 	 */
-	if ((m->flags & PG_WRITEABLE) == 0)
+	if ((m->aflags & PGA_WRITEABLE) == 0)
 		return;
 	moea_clear_bit(m, PTE_CHG);
 }
@@ -1323,13 +1323,13 @@ moea_remove_write(mmu_t mmu, vm_page_t m)
 	    ("moea_remove_write: page %p is not managed", m));
 
 	/*
-	 * If the page is not VPO_BUSY, then PG_WRITEABLE cannot be set by
-	 * another thread while the object is locked.  Thus, if PG_WRITEABLE
+	 * 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.
 	 */
 	VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
 	if ((m->oflags & VPO_BUSY) == 0 &&
-	    (m->flags & PG_WRITEABLE) == 0)
+	    (m->aflags & PGA_WRITEABLE) == 0)
 		return;
 	vm_page_lock_queues();
 	lo = moea_attr_fetch(m);
@@ -1356,7 +1356,7 @@ moea_remove_write(mmu_t mmu, vm_page_t m)
 		moea_attr_clear(m, PTE_CHG);
 		vm_page_dirty(m);
 	}
-	vm_page_flag_clear(m, PG_WRITEABLE);
+	vm_page_aflag_clear(m, PGA_WRITEABLE);
 	vm_page_unlock_queues();
 }
 
@@ -1794,11 +1794,11 @@ moea_remove_all(mmu_t mmu, vm_page_t m)
 		moea_pvo_remove(pvo, -1);
 		PMAP_UNLOCK(pmap);
 	}
-	if ((m->flags & PG_WRITEABLE) && moea_is_modified(mmu, m)) {
+	if ((m->aflags & PGA_WRITEABLE) && moea_is_modified(mmu, m)) {
 		moea_attr_clear(m, PTE_CHG);
 		vm_page_dirty(m);
 	}
-	vm_page_flag_clear(m, PG_WRITEABLE);
+	vm_page_aflag_clear(m, PGA_WRITEABLE);
 	vm_page_unlock_queues();
 }
 
diff --git a/sys/powerpc/aim/mmu_oea64.c b/sys/powerpc/aim/mmu_oea64.c
index 0a10ce8..7500462 100644
--- a/sys/powerpc/aim/mmu_oea64.c
+++ b/sys/powerpc/aim/mmu_oea64.c
@@ -1239,7 +1239,7 @@ moea64_enter_locked(mmu_t mmu, pmap_t pmap, vm_offset_t va, vm_page_t m,
 		pte_lo |= LPTE_BW;
 		if (pmap_bootstrapped &&
 		    (m->oflags & VPO_UNMANAGED) == 0)
-			vm_page_flag_set(m, PG_WRITEABLE);
+			vm_page_aflag_set(m, PGA_WRITEABLE);
 	} else
 		pte_lo |= LPTE_BR;
 
@@ -1484,13 +1484,13 @@ moea64_is_modified(mmu_t mmu, vm_page_t m)
 	    ("moea64_is_modified: page %p is not managed", m));
 
 	/*
-	 * If the page is not VPO_BUSY, then PG_WRITEABLE cannot be
-	 * concurrently set while the object is locked.  Thus, if PG_WRITEABLE
+	 * If the page is not VPO_BUSY, then PGA_WRITEABLE cannot be
+	 * concurrently set while the object is locked.  Thus, if PGA_WRITEABLE
 	 * is clear, no PTEs can have LPTE_CHG set.
 	 */
 	VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
 	if ((m->oflags & VPO_BUSY) == 0 &&
-	    (m->flags & PG_WRITEABLE) == 0)
+	    (m->aflags & PGA_WRITEABLE) == 0)
 		return (FALSE);
 	return (moea64_query_bit(mmu, m, LPTE_CHG));
 }
@@ -1528,11 +1528,11 @@ moea64_clear_modify(mmu_t mmu, vm_page_t m)
 	    ("moea64_clear_modify: page %p is busy", m));
 
 	/*
-	 * If the page is not PG_WRITEABLE, then no PTEs can have LPTE_CHG
+	 * If the page is not PGA_WRITEABLE, then no PTEs can have LPTE_CHG
 	 * set.  If the object containing the page is locked and the page is
-	 * not VPO_BUSY, then PG_WRITEABLE cannot be concurrently set.
+	 * not VPO_BUSY, then PGA_WRITEABLE cannot be concurrently set.
 	 */
-	if ((m->flags & PG_WRITEABLE) == 0)
+	if ((m->aflags & PGA_WRITEABLE) == 0)
 		return;
 	moea64_clear_bit(mmu, m, LPTE_CHG);
 }
@@ -1552,13 +1552,13 @@ moea64_remove_write(mmu_t mmu, vm_page_t m)
 	    ("moea64_remove_write: page %p is not managed", m));
 
 	/*
-	 * If the page is not VPO_BUSY, then PG_WRITEABLE cannot be set by
-	 * another thread while the object is locked.  Thus, if PG_WRITEABLE
+	 * 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.
 	 */
 	VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
 	if ((m->oflags & VPO_BUSY) == 0 &&
-	    (m->flags & PG_WRITEABLE) == 0)
+	    (m->aflags & PGA_WRITEABLE) == 0)
 		return;
 	vm_page_lock_queues();
 	lo = moea64_attr_fetch(m);
@@ -1588,7 +1588,7 @@ moea64_remove_write(mmu_t mmu, vm_page_t m)
 		moea64_attr_clear(m, LPTE_CHG);
 		vm_page_dirty(m);
 	}
-	vm_page_flag_clear(m, PG_WRITEABLE);
+	vm_page_aflag_clear(m, PGA_WRITEABLE);
 	vm_page_unlock_queues();
 }
 
@@ -2064,11 +2064,11 @@ moea64_remove_all(mmu_t mmu, vm_page_t m)
 		moea64_pvo_remove(mmu, pvo);
 		PMAP_UNLOCK(pmap);
 	}
-	if ((m->flags & PG_WRITEABLE) && moea64_is_modified(mmu, m)) {
+	if ((m->aflags & PGA_WRITEABLE) && moea64_is_modified(mmu, m)) {
 		moea64_attr_clear(m, LPTE_CHG);
 		vm_page_dirty(m);
 	}
-	vm_page_flag_clear(m, PG_WRITEABLE);
+	vm_page_aflag_clear(m, PGA_WRITEABLE);
 	vm_page_unlock_queues();
 }