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)

1 files changed, 16 insertions, 16 deletions

diff --git a/sys/arm/arm/pmap.c b/sys/arm/arm/pmap.c
index 38733c9..28835ec 100644
--- a/sys/arm/arm/pmap.c
+++ b/sys/arm/arm/pmap.c
@@ -1402,7 +1402,7 @@ pmap_fix_cache(struct vm_page *pg, pmap_t pm, vm_offset_t va)
 
 	if ((kwritable == 0) && (writable == 0)) {
 		pg->md.pvh_attrs &= ~PVF_MOD;
-		vm_page_flag_clear(pg, PG_WRITEABLE);
+		vm_page_aflag_clear(pg, PGA_WRITEABLE);
 		return;
 	}
 }
@@ -1568,7 +1568,7 @@ pmap_clearbit(struct vm_page *pg, u_int maskbits)
 	}
 
 	if (maskbits & PVF_WRITE)
-		vm_page_flag_clear(pg, PG_WRITEABLE);
+		vm_page_aflag_clear(pg, PGA_WRITEABLE);
 	vm_page_unlock_queues();
 	return (count);
 }
@@ -1630,7 +1630,7 @@ pmap_enter_pv(struct vm_page *pg, struct pv_entry *pve, pmap_t pm,
 	pg->md.pvh_attrs |= flags & (PVF_REF | PVF_MOD);
 	if (pve->pv_flags & PVF_WIRED)
 		++pm->pm_stats.wired_count;
-	vm_page_flag_set(pg, PG_REFERENCED);
+	vm_page_aflag_set(pg, PGA_REFERENCED);
 }
 
 /*
@@ -1699,7 +1699,7 @@ pmap_nuke_pv(struct vm_page *pg, pmap_t pm, struct pv_entry *pve)
 	if (TAILQ_FIRST(&pg->md.pv_list) == NULL)
 		pg->md.pvh_attrs &= ~PVF_REF;
        	else
-		vm_page_flag_set(pg, PG_REFERENCED);
+		vm_page_aflag_set(pg, PGA_REFERENCED);
 	if ((pve->pv_flags & PVF_NC) && ((pm == pmap_kernel()) ||
 	     (pve->pv_flags & PVF_WRITE) || !(pve->pv_flags & PVF_MWC)))
 		pmap_fix_cache(pg, pm, 0);
@@ -1709,7 +1709,7 @@ pmap_nuke_pv(struct vm_page *pg, pmap_t pm, struct pv_entry *pve)
 			    break;
 		if (!pve) {
 			pg->md.pvh_attrs &= ~PVF_MOD;
-			vm_page_flag_clear(pg, PG_WRITEABLE);
+			vm_page_aflag_clear(pg, PGA_WRITEABLE);
 		}
 	}
 	pv = TAILQ_FIRST(&pg->md.pv_list);
@@ -1724,7 +1724,7 @@ pmap_nuke_pv(struct vm_page *pg, pmap_t pm, struct pv_entry *pve)
 			--pm->pm_stats.wired_count;
 		pg->md.pvh_attrs &= ~PVF_REF;
 		pg->md.pvh_attrs &= ~PVF_MOD;
-		vm_page_flag_clear(pg, PG_WRITEABLE);
+		vm_page_aflag_clear(pg, PGA_WRITEABLE);
 		pmap_free_pv_entry(pv);
 	}
 }
@@ -2695,7 +2695,7 @@ pmap_remove_pages(pmap_t pmap)
 		npv = TAILQ_NEXT(pv, pv_plist);
 		pmap_nuke_pv(m, pmap, pv);
 		if (TAILQ_EMPTY(&m->md.pv_list))
-			vm_page_flag_clear(m, PG_WRITEABLE);
+			vm_page_aflag_clear(m, PGA_WRITEABLE);
 		pmap_free_pv_entry(pv);
 		pmap_free_l2_bucket(pmap, l2b, 1);
 	}
@@ -3172,7 +3172,7 @@ pmap_remove_all(vm_page_t m)
 		else
 			pmap_tlb_flushD(curpm);
 	}
-	vm_page_flag_clear(m, PG_WRITEABLE);
+	vm_page_aflag_clear(m, PGA_WRITEABLE);
 	vm_page_unlock_queues();
 }
 
@@ -3406,7 +3406,7 @@ do_l2b_alloc:
 				vm_page_dirty(m);
 		}
 		if (m && opte)
-			vm_page_flag_set(m, PG_REFERENCED);
+			vm_page_aflag_set(m, PGA_REFERENCED);
 	} else {
 		/*
 		 * Need to do page referenced emulation.
@@ -3418,7 +3418,7 @@ do_l2b_alloc:
 		npte |= L2_S_PROT_W;
 		if (m != NULL &&
 		    (m->oflags & VPO_UNMANAGED) == 0)
-			vm_page_flag_set(m, PG_WRITEABLE);
+			vm_page_aflag_set(m, PGA_WRITEABLE);
 	}
 	npte |= pte_l2_s_cache_mode;
 	if (m && m == opg) {
@@ -4505,11 +4505,11 @@ pmap_clear_modify(vm_page_t m)
 	    ("pmap_clear_modify: page %p is busy", m));
 
 	/*
-	 * If the page is not PG_WRITEABLE, then no mappings can be modified.
+	 * If the page is not PGA_WRITEABLE, then no mappings can be modified.
 	 * If the object containing the page is locked and the page is not
-	 * VPO_BUSY, then PG_WRITEABLE cannot be concurrently set.
+	 * VPO_BUSY, then PGA_WRITEABLE cannot be concurrently set.
 	 */
-	if ((m->flags & PG_WRITEABLE) == 0)
+	if ((m->aflags & PGA_WRITEABLE) == 0)
 		return;
 	if (m->md.pvh_attrs & PVF_MOD)
 		pmap_clearbit(m, PVF_MOD);
@@ -4558,13 +4558,13 @@ pmap_remove_write(vm_page_t m)
 	    ("pmap_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)
 		pmap_clearbit(m, PVF_WRITE);
 }