Introduce a global lock for the vm subsystem (vm_mtx).

vm_mtx does not recurse and is required for most low level
vm operations.

faults can not be taken without holding Giant.

Memory subsystems can now call the base page allocators safely.

Almost all atomic ops were removed as they are covered under the
vm mutex.

Alpha and ia64 now need to catch up to i386's trap handlers.

FFS and NFS have been tested, other filesystems will need minor
changes (grabbing the vm lock when twiddling page properties).

Reviewed (partially) by: jake, jhb

1 files changed, 14 insertions, 1 deletions

diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c
index 2f4dc8d..6c050ba 100644
--- a/sys/kern/vfs_subr.c
+++ b/sys/kern/vfs_subr.c
@@ -711,6 +711,8 @@ vinvalbuf(vp, flags, cred, p, slpflag, slptimeo)
 	int s, error;
 	vm_object_t object;
 
+	mtx_assert(&vm_mtx, MA_NOTOWNED);
+
 	if (flags & V_SAVE) {
 		s = splbio();
 		while (vp->v_numoutput) {
@@ -797,8 +799,10 @@ vinvalbuf(vp, flags, cred, p, slpflag, slptimeo)
 	 */
 	mtx_lock(&vp->v_interlock);
 	if (VOP_GETVOBJECT(vp, &object) == 0) {
+		mtx_lock(&vm_mtx);
 		vm_object_page_remove(object, 0, 0,
 			(flags & V_SAVE) ? TRUE : FALSE);
+		mtx_unlock(&vm_mtx);
 	}
 	mtx_unlock(&vp->v_interlock);
 
@@ -1132,6 +1136,8 @@ speedup_syncer()
  * Also sets B_PAGING flag to indicate that vnode is not fully associated
  * with the buffer.  i.e. the bp has not been linked into the vnode or
  * ref-counted.
+ *
+ * Doesn't block, only vnode seems to need a lock.
  */
 void
 pbgetvp(vp, bp)
@@ -1554,6 +1560,7 @@ vput(vp)
 {
 	struct proc *p = curproc;	/* XXX */
 
+	mtx_assert(&Giant, MA_OWNED);
 	KASSERT(vp != NULL, ("vput: null vp"));
 	mtx_lock(&vp->v_interlock);
 	/* Skip this v_writecount check if we're going to panic below. */
@@ -2382,7 +2389,11 @@ loop:
 			if (!vget(vp,
 				LK_INTERLOCK | LK_EXCLUSIVE | LK_RETRY | LK_NOOBJ, curproc)) {
 				if (VOP_GETVOBJECT(vp, &obj) == 0) {
-					vm_object_page_clean(obj, 0, 0, flags == MNT_WAIT ? OBJPC_SYNC : OBJPC_NOSYNC);
+					mtx_lock(&vm_mtx);
+					vm_object_page_clean(obj, 0, 0,
+					    flags == MNT_WAIT ?
+					    OBJPC_SYNC : OBJPC_NOSYNC);
+					mtx_unlock(&vm_mtx);
 					anyio = 1;
 				}
 				vput(vp);
@@ -2409,6 +2420,8 @@ vfs_object_create(vp, p, cred)
 	struct proc *p;
 	struct ucred *cred;
 {
+
+	mtx_assert(&vm_mtx, MA_NOTOWNED);
 	return (VOP_CREATEVOBJECT(vp, cred, p));
 }