new locking scheme

[unix-history] / usr / src / sys / miscfs / union / union_subr.c

diff --git a/usr/src/sys/miscfs/union/union_subr.c b/usr/src/sys/miscfs/union/union_subr.c
index 5e13601..3319a34 100644 (file)
--- a/usr/src/sys/miscfs/union/union_subr.c
+++ b/usr/src/sys/miscfs/union/union_subr.c
@@ -8,7 +8,7 @@
  *
  * %sccs.include.redist.c%
  *
  *
  * %sccs.include.redist.c%
  *

- *     @(#)union_subr.c        1.9 (Berkeley) %G%
+ *     @(#)union_subr.c        2.1 (Berkeley) %G%

  */
 
 #include <sys/param.h>
  */
 
 #include <sys/param.h>


@@ -37,6 +37,20 @@ union_init()
        unvplock = 0;
 }
 
        unvplock = 0;
 }
 

+static void
+union_remlist(un)
+       struct union_node *un;
+{
+       struct union_node **unpp;
+
+       for (unpp = &unhead; *unpp != 0; unpp = &(*unpp)->un_next) {
+               if (*unpp == un) {
+                       *unpp = un->un_next;
+                       break;
+               }
+       }
+}
+

 /*
  * allocate a union_node/vnode pair.  the vnode is
  * referenced and locked.  the new vnode is returned
 /*
  * allocate a union_node/vnode pair.  the vnode is
  * referenced and locked.  the new vnode is returned


@@ -47,6 +61,7 @@ union_init()
  * layer object to be created at a later time.  (uppervp)
  * and (lowervp) reference the upper and lower layer objects
  * being mapped.  either, but not both, can be nil.
  * layer object to be created at a later time.  (uppervp)
  * and (lowervp) reference the upper and lower layer objects
  * being mapped.  either, but not both, can be nil.

+ * if supplied, (uppervp) is locked.

  * the reference is either maintained in the new union_node
  * object which is allocated, or they are vrele'd.
  *
  * the reference is either maintained in the new union_node
  * object which is allocated, or they are vrele'd.
  *


@@ -99,50 +114,102 @@ loop:
                    (UNIONTOV(un)->v_mount == mp)) {
                        if (vget(UNIONTOV(un), 0))
                                goto loop;
                    (UNIONTOV(un)->v_mount == mp)) {
                        if (vget(UNIONTOV(un), 0))
                                goto loop;

-                       if (UNIONTOV(un) != undvp)
-                               VOP_LOCK(UNIONTOV(un));
+                       break;
+               }
+       }

 
 

+       if (un) {
+               /*
+                * Obtain a lock on the union_node.
+                * uppervp is locked, though un->un_uppervp
+                * may not be.  this doesn't break the locking
+                * hierarchy since in the case that un->un_uppervp
+                * is not yet locked it will be vrele'd and replaced
+                * with uppervp.
+                */
+
+               if ((dvp != NULLVP) && (uppervp == dvp)) {

                        /*
                        /*

-                        * Save information about the upper layer.
+                        * Access ``.'', so (un) will already
+                        * be locked.  Since this process has
+                        * the lock on (uppervp) no other
+                        * process can hold the lock on (un).

                         */
                         */

-                       if (uppervp != un->un_uppervp) {
-                               if (un->un_uppervp)
-                                       vrele(un->un_uppervp);
-                               un->un_uppervp = uppervp;
-                       } else if (uppervp) {
-                               vrele(uppervp);
+#ifdef DIAGNOSTIC
+                       if ((un->un_flags & UN_LOCKED) == 0)
+                               panic("union: . not locked");
+                       else if (curproc && un->un_pid != curproc->p_pid &&
+                                   un->un_pid > -1 && curproc->p_pid > -1)
+                               panic("union: allocvp not lock owner");
+#endif
+               } else {
+                       if (un->un_flags & UN_LOCKED) {
+                               vrele(UNIONTOV(un));
+                               un->un_flags |= UN_WANT;
+                               sleep((caddr_t) &un->un_flags, PINOD);
+                               goto loop;

                        }
                        }

+                       un->un_flags |= UN_LOCKED;

 
 

-                       /*
-                        * Save information about the lower layer.
-                        * This needs to keep track of pathname
-                        * and directory information which union_vn_create
-                        * might need.
-                        */
-                       if (lowervp != un->un_lowervp) {
-                               if (un->un_lowervp) {
-                                       vrele(un->un_lowervp);
-                                       free(un->un_path, M_TEMP);
-                                       vrele(un->un_dirvp);
-                               }
-                               un->un_lowervp = lowervp;
-                               if (cnp && (lowervp != NULLVP) &&
-                                   (lowervp->v_type == VREG)) {
-                                       un->un_hash = cnp->cn_hash;
-                                       un->un_path = malloc(cnp->cn_namelen+1,
-                                                       M_TEMP, M_WAITOK);
-                                       bcopy(cnp->cn_nameptr, un->un_path,
-                                                       cnp->cn_namelen);
-                                       un->un_path[cnp->cn_namelen] = '\0';
-                                       VREF(dvp);
-                                       un->un_dirvp = dvp;
-                               }
-                       } else if (lowervp) {
-                               vrele(lowervp);
+#ifdef DIAGNOSTIC
+                       if (curproc)
+                               un->un_pid = curproc->p_pid;
+                       else
+                               un->un_pid = -1;
+#endif
+               }
+
+               /*
+                * At this point, the union_node is locked,
+                * un->un_uppervp may not be locked, and uppervp
+                * is locked or nil.
+                */
+
+               /*
+                * Save information about the upper layer.
+                */
+               if (uppervp != un->un_uppervp) {
+                       if (un->un_uppervp)
+                               vrele(un->un_uppervp);
+                       un->un_uppervp = uppervp;
+               } else if (uppervp) {
+                       vrele(uppervp);
+               }
+
+               if (un->un_uppervp) {
+                       un->un_flags |= UN_ULOCK;
+                       un->un_flags &= ~UN_KLOCK;
+               }
+
+               /*
+                * Save information about the lower layer.
+                * This needs to keep track of pathname
+                * and directory information which union_vn_create
+                * might need.
+                */
+               if (lowervp != un->un_lowervp) {
+                       if (un->un_lowervp) {
+                               vrele(un->un_lowervp);
+                               free(un->un_path, M_TEMP);
+                               vrele(un->un_dirvp);
+                       }
+                       un->un_lowervp = lowervp;
+                       if (cnp && (lowervp != NULLVP) &&
+                           (lowervp->v_type == VREG)) {
+                               un->un_hash = cnp->cn_hash;
+                               un->un_path = malloc(cnp->cn_namelen+1,
+                                               M_TEMP, M_WAITOK);
+                               bcopy(cnp->cn_nameptr, un->un_path,
+                                               cnp->cn_namelen);
+                               un->un_path[cnp->cn_namelen] = '\0';
+                               VREF(dvp);
+                               un->un_dirvp = dvp;

                        }
                        }

-                       *vpp = UNIONTOV(un);
-                       return (0);
+               } else if (lowervp) {
+                       vrele(lowervp);

                }
                }

+               *vpp = UNIONTOV(un);
+               return (0);

        }
 
        /*
        }
 
        /*


@@ -157,8 +224,18 @@ loop:
        unvplock |= UN_LOCKED;
 
        error = getnewvnode(VT_UNION, mp, union_vnodeop_p, vpp);
        unvplock |= UN_LOCKED;
 
        error = getnewvnode(VT_UNION, mp, union_vnodeop_p, vpp);

-       if (error)
+       if (error) {
+               if (uppervp) {
+                       if (dvp == uppervp)
+                               vrele(uppervp);
+                       else
+                               vput(uppervp);
+               }
+               if (lowervp)
+                       vrele(lowervp);
+

                goto out;
                goto out;

+       }

 
        MALLOC((*vpp)->v_data, void *, sizeof(struct union_node),
                M_TEMP, M_WAITOK);
 
        MALLOC((*vpp)->v_data, void *, sizeof(struct union_node),
                M_TEMP, M_WAITOK);


@@ -173,7 +250,15 @@ loop:
        un->un_uppervp = uppervp;
        un->un_lowervp = lowervp;
        un->un_openl = 0;
        un->un_uppervp = uppervp;
        un->un_lowervp = lowervp;
        un->un_openl = 0;

-       un->un_flags = 0;
+       un->un_flags = UN_LOCKED;
+       if (un->un_uppervp)
+               un->un_flags |= UN_ULOCK;
+#ifdef DIAGNOSTIC
+       if (curproc)
+               un->un_pid = curproc->p_pid;
+       else
+               un->un_pid = -1;
+#endif

        if (cnp && (lowervp != NULLVP) && (lowervp->v_type == VREG)) {
                un->un_hash = cnp->cn_hash;
                un->un_path = malloc(cnp->cn_namelen+1, M_TEMP, M_WAITOK);
        if (cnp && (lowervp != NULLVP) && (lowervp->v_type == VREG)) {
                un->un_hash = cnp->cn_hash;
                un->un_path = malloc(cnp->cn_namelen+1, M_TEMP, M_WAITOK);


@@ -192,12 +277,6 @@ loop:
                continue;
        *pp = un;
 
                continue;
        *pp = un;
 

-       un->un_flags |= UN_LOCKED;
-
-#ifdef DIAGNOSTIC
-       un->un_pid = curproc->p_pid;
-#endif
-

        if (xlowervp)
                vrele(xlowervp);
 
        if (xlowervp)
                vrele(xlowervp);
 


@@ -216,15 +295,9 @@ int
 union_freevp(vp)
        struct vnode *vp;
 {
 union_freevp(vp)
        struct vnode *vp;
 {

-       struct union_node **unpp;

        struct union_node *un = VTOUNION(vp);
 
        struct union_node *un = VTOUNION(vp);
 

-       for (unpp = &unhead; *unpp != 0; unpp = &(*unpp)->un_next) {
-               if (*unpp == un) {
-                       *unpp = un->un_next;
-                       break;
-               }
-       }
+       union_remlist(un);

 
        FREE(vp->v_data, M_TEMP);
        vp->v_data = 0;
 
        FREE(vp->v_data, M_TEMP);
        vp->v_data = 0;


@@ -504,7 +577,12 @@ void
 union_removed_upper(un)
        struct union_node *un;
 {
 union_removed_upper(un)
        struct union_node *un;
 {

-       vrele(un->un_uppervp);
+       if (un->un_flags & UN_ULOCK) {
+               un->un_flags &= ~UN_ULOCK;
+               vput(un->un_uppervp);
+       } else {
+               vrele(un->un_uppervp);
+       }

        un->un_uppervp = NULLVP;
 }
 
        un->un_uppervp = NULLVP;
 }