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Date:      Sat, 18 May 2013 22:42:05 +0000 (UTC)
From:      Attilio Rao <attilio@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-user@freebsd.org
Subject:   svn commit: r250790 - user/attilio/vmobj-readlock/sys/vm
Message-ID:  <201305182242.r4IMg566064006@svn.freebsd.org>
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Author: attilio
Date: Sat May 18 22:42:05 2013
New Revision: 250790
URL: http://svnweb.freebsd.org/changeset/base/250790

Log:
  Convert vm_map_pmap_enter() to work with read lock for most of the
  cases.
  
  Sponsored by:	EMC / Isilon storage division

Modified:
  user/attilio/vmobj-readlock/sys/vm/vm_map.c
  user/attilio/vmobj-readlock/sys/vm/vm_object.h

Modified: user/attilio/vmobj-readlock/sys/vm/vm_map.c
==============================================================================
--- user/attilio/vmobj-readlock/sys/vm/vm_map.c	Sat May 18 22:16:42 2013	(r250789)
+++ user/attilio/vmobj-readlock/sys/vm/vm_map.c	Sat May 18 22:42:05 2013	(r250790)
@@ -1806,18 +1806,27 @@ vm_map_pmap_enter(vm_map_t map, vm_offse
 
 	if ((prot & (VM_PROT_READ | VM_PROT_EXECUTE)) == 0 || object == NULL)
 		return;
-	VM_OBJECT_WLOCK(object);
+	VM_OBJECT_RLOCK(object);
 	if (object->type == OBJT_DEVICE || object->type == OBJT_SG) {
-		pmap_object_init_pt(map->pmap, addr, object, pindex, size);
-		goto unlock_return;
+		VM_OBJECT_RUNLOCK(object);
+		VM_OBJECT_WLOCK(object);
+		if (object->type == OBJT_DEVICE || object->type == OBJT_SG) {
+			pmap_object_init_pt(map->pmap, addr, object, pindex,
+			    size);
+			VM_OBJECT_WUNLOCK(object);
+			return;
+		}
+		VM_OBJECT_LOCK_DOWNGRADE(object);
 	}
 
 	psize = atop(size);
 	if (psize > MAX_INIT_PT && (flags & MAP_PREFAULT_PARTIAL) != 0)
 		psize = MAX_INIT_PT;
 	if (psize + pindex > object->size) {
-		if (object->size < pindex)
-			goto unlock_return;
+		if (object->size < pindex) {
+			VM_OBJECT_RUNLOCK(object);
+			return;
+		}
 		psize = object->size - pindex;
 	}
 
@@ -1856,8 +1865,7 @@ vm_map_pmap_enter(vm_map_t map, vm_offse
 	if (p_start != NULL)
 		pmap_enter_object(map->pmap, start, addr + ptoa(psize),
 		    p_start, prot);
-unlock_return:
-	VM_OBJECT_WUNLOCK(object);
+	VM_OBJECT_RUNLOCK(object);
 }
 
 /*

Modified: user/attilio/vmobj-readlock/sys/vm/vm_object.h
==============================================================================
--- user/attilio/vmobj-readlock/sys/vm/vm_object.h	Sat May 18 22:16:42 2013	(r250789)
+++ user/attilio/vmobj-readlock/sys/vm/vm_object.h	Sat May 18 22:42:05 2013	(r250790)
@@ -223,6 +223,8 @@ extern struct vm_object kmem_object_stor
 	rw_assert(&(object)->lock, RA_RLOCKED)
 #define	VM_OBJECT_ASSERT_WLOCKED(object)				\
 	rw_assert(&(object)->lock, RA_WLOCKED)
+#define	VM_OBJECT_LOCK_DOWNGRADE(object)				\
+	rw_downgrade(&(object)->lock)
 #define	VM_OBJECT_RLOCK(object)						\
 	rw_rlock(&(object)->lock)
 #define	VM_OBJECT_RUNLOCK(object)					\

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