nullfs: reduce areas protected by vnode interlock in null_lock

Similarly to the other routine stop taking the interlock for the lower
vnode. The interlock for nullfs vnode is still taken to ensure
stability of ->v_data.

Reviewed by:	kib
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D21480

diff --git a/sys/fs/nullfs/null_vnops.c b/sys/fs/nullfs/null_vnops.c
index 29237a5239b955c9d1d238c0152e510665e1a4a7..7b01da41b15e6a5f8f87f633eb830c06bd2072f2 100644 (file)
--- a/sys/fs/nullfs/null_vnops.c
+++ b/sys/fs/nullfs/null_vnops.c
@@ -638,16 +638,16 @@ static int
 null_lock(struct vop_lock1_args *ap)
 {
        struct vnode *vp = ap->a_vp;
-       int flags = ap->a_flags;
+       int flags;
        struct null_node *nn;
        struct vnode *lvp;
        int error;
 
-
-       if ((flags & LK_INTERLOCK) == 0) {
+       if ((ap->a_flags & LK_INTERLOCK) == 0)
                VI_LOCK(vp);
-               ap->a_flags = flags |= LK_INTERLOCK;
-       }
+       else
+               ap->a_flags &= ~LK_INTERLOCK;
+       flags = ap->a_flags;
        nn = VTONULL(vp);
        /*
         * If we're still active we must ask the lower layer to
@@ -655,8 +655,6 @@ null_lock(struct vop_lock1_args *ap)
         * vop lock.
         */
        if (nn != NULL && (lvp = NULLVPTOLOWERVP(vp)) != NULL) {
-               VI_LOCK_FLAGS(lvp, MTX_DUPOK);
-               VI_UNLOCK(vp);
                /*
                 * We have to hold the vnode here to solve a potential
                 * reclaim race.  If we're forcibly vgone'd while we
@@ -669,6 +667,7 @@ null_lock(struct vop_lock1_args *ap)
                 * here.
                 */
                vholdnz(lvp);
+               VI_UNLOCK(vp);
                error = VOP_LOCK(lvp, flags);
 
                /*
@@ -678,7 +677,7 @@ null_lock(struct vop_lock1_args *ap)
                 * case by reacquiring correct lock in requested mode.
                 */
                if (VTONULL(vp) == NULL && error == 0) {
-                       ap->a_flags &= ~(LK_TYPE_MASK | LK_INTERLOCK);
+                       ap->a_flags &= ~LK_TYPE_MASK;
                        switch (flags & LK_TYPE_MASK) {
                        case LK_SHARED:
                                ap->a_flags |= LK_SHARED;
@@ -695,8 +694,10 @@ null_lock(struct vop_lock1_args *ap)
                        error = vop_stdlock(ap);
                }
                vdrop(lvp);
-       } else
+       } else {
+               VI_UNLOCK(vp);
                error = vop_stdlock(ap);
+       }
 
        return (error);
 }