svn commit: r315475 - in stable/11/sys: kern vm

[Alan Cox]

Author: alc
Date: Sat Mar 18 05:53:09 2017
New Revision: 315475
URL: https://svnweb.freebsd.org/changeset/base/315475

Log:
  MFC r315318
    Relax the locking requirements for vm_object_page_noreuse().  While
    reviewing all uses of OFF_TO_IDX(), I observed that
    vm_object_page_noreuse() is requiring an exclusive lock on the object
    when, in fact, a shared lock suffices.

Modified:
  stable/11/sys/kern/vfs_default.c
  stable/11/sys/vm/vm_object.c
Directory Properties:
  stable/11/   (props changed)

Modified: stable/11/sys/kern/vfs_default.c
==============================================================================
--- stable/11/sys/kern/vfs_default.c	Sat Mar 18 05:48:26 2017	(r315474)
+++ stable/11/sys/kern/vfs_default.c	Sat Mar 18 05:53:09 2017	(r315475)
@@ -1100,10 +1100,10 @@ vop_stdadvise(struct vop_advise_args *ap
 		if (vp->v_object != NULL) {
 			start = trunc_page(ap->a_start);
 			end = round_page(ap->a_end);
-			VM_OBJECT_WLOCK(vp->v_object);
+			VM_OBJECT_RLOCK(vp->v_object);
 			vm_object_page_noreuse(vp->v_object, OFF_TO_IDX(start),
 			    OFF_TO_IDX(end));
-			VM_OBJECT_WUNLOCK(vp->v_object);
+			VM_OBJECT_RUNLOCK(vp->v_object);
 		}
 
 		bo = &vp->v_bufobj;

Modified: stable/11/sys/vm/vm_object.c
==============================================================================
--- stable/11/sys/vm/vm_object.c	Sat Mar 18 05:48:26 2017	(r315474)
+++ stable/11/sys/vm/vm_object.c	Sat Mar 18 05:53:09 2017	(r315475)
@@ -1977,7 +1977,7 @@ vm_object_page_noreuse(vm_object_t objec
 	struct mtx *mtx, *new_mtx;
 	vm_page_t p, next;
 
-	VM_OBJECT_ASSERT_WLOCKED(object);
+	VM_OBJECT_ASSERT_LOCKED(object);
 	KASSERT((object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0,
 	    ("vm_object_page_noreuse: illegal object %p", object));
 	if (object->resident_page_count == 0)