struct vcache *vcp;
struct vnode *vp, *dvp;
int flags = ap->a_cnp->cn_flags;
- int lockparent; /* 1 => lockparent flag is set */
dvp = ap->a_dvp;
if (dvp->v_type != VDIR) {
GETNAME();
- lockparent = flags & LOCKPARENT;
-
#if __FreeBSD_version < 1000021
cnp->cn_flags |= MPSAFE; /* steel */
#endif
+ /*
+ * Locking rules:
+ *
+ * - 'dvp' is locked by our caller. We must return it locked, whether we
+ * return success or error.
+ *
+ * - If the lookup succeeds, 'vp' must be locked before we return.
+ *
+ * - If we lock multiple vnodes, parent vnodes must be locked before
+ * children vnodes.
+ *
+ * As a result, looking up the parent directory (if 'flags' has ISDOTDOT
+ * set) is a bit of a special case. In that case, we must unlock 'dvp'
+ * before performing the lookup, since the lookup operation may lock the
+ * target vnode, and the target vnode is the parent of 'dvp' (so we must
+ * lock 'dvp' after locking the target vnode).
+ */
+
if (flags & ISDOTDOT)
MA_VOP_UNLOCK(dvp, 0, p);
}
vp = AFSTOV(vcp); /* always get a node if no error */
- /* The parent directory comes in locked. We unlock it on return
- * unless the caller wants it left locked.
- * we also always return the vnode locked. */
-
if (flags & ISDOTDOT) {
- /* vp before dvp since we go root to leaf, and .. comes first */
+ /* Must lock 'vp' before 'dvp', since 'vp' is the parent vnode. */
ma_vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p);
ma_vn_lock(dvp, LK_EXCLUSIVE | LK_RETRY, p);
- /* always return the child locked */
- if (lockparent && (flags & ISLASTCN)
- && (error = ma_vn_lock(dvp, LK_EXCLUSIVE, p))) {
- vput(vp);
- DROPNAME();
- return (error);
- }
} else if (vp == dvp) {
/* they're the same; afs_lookup() already ref'ed the leaf.
* It came in locked, so we don't need to ref OR lock it */
} else {
ma_vn_lock(vp, LK_EXCLUSIVE | LK_CANRECURSE | LK_RETRY, p);
- /* always return the child locked */
}
*ap->a_vpp = vp;