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From: Attilio Rao <attilio@FreeBSD.org>
Date: Tue, 21 May 2013 17:40:22 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-user@freebsd.org
Subject: svn commit: r250862 - user/attilio/vmobj-readlock/sys/vm
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Author: attilio
Date: Tue May 21 17:40:22 2013
New Revision: 250862
URL: http://svnweb.freebsd.org/changeset/base/250862

Log:
  Reinsert VM_OBJECT_LOCK_DOWNGRADE().
  
  Sponsored by:	EMC / Isilon storage division
  Requested by:	alc

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	Tue May 21 17:30:27 2013	(r250861)
+++ user/attilio/vmobj-readlock/sys/vm/vm_map.c	Tue May 21 17:40:22 2013	(r250862)
@@ -1806,7 +1806,6 @@ vm_map_pmap_enter(vm_map_t map, vm_offse
 
 	if ((prot & (VM_PROT_READ | VM_PROT_EXECUTE)) == 0 || object == NULL)
 		return;
-relock:
 	VM_OBJECT_RLOCK(object);
 	if (object->type == OBJT_DEVICE || object->type == OBJT_SG) {
 		VM_OBJECT_RUNLOCK(object);
@@ -1817,8 +1816,7 @@ relock:
 			VM_OBJECT_WUNLOCK(object);
 			return;
 		}
-		VM_OBJECT_WUNLOCK(object);
-		goto relock;
+		VM_OBJECT_LOCK_DOWNGRADE(object);
 	}
 
 	psize = atop(size);

Modified: user/attilio/vmobj-readlock/sys/vm/vm_object.h
==============================================================================
--- user/attilio/vmobj-readlock/sys/vm/vm_object.h	Tue May 21 17:30:27 2013	(r250861)
+++ user/attilio/vmobj-readlock/sys/vm/vm_object.h	Tue May 21 17:40:22 2013	(r250862)
@@ -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)					\