vol-package-avoid-race-on-invalidating-hashed-vnode-20030111

thanks to whichever of jhutz@cmu.edu or cg2v@andrew.cmu.edu (or both)
noticed the race; also deal with wrap problem in VolumeCacheCheck that i
noticed

diff --git a/src/vol/vnode.c b/src/vol/vnode.c
index d385631..ee3e663 100644 (file)
--- a/src/vol/vnode.c
+++ b/src/vol/vnode.c
@@ -641,7 +641,7 @@ Vnode *VGetVnode_r(ec,vp,vnodeNumber,locktype)
     /* Check that the vnode hasn't been removed while we were obtaining
        the lock */
     VNLog(102, 2, vnodeNumber, (afs_int32) vnp);
-    if (vnp->disk.type == vNull) {
+    if ((vnp->disk.type == vNull) || (vnp->cacheCheck == 0)){
        if (vnp->nUsers-- == 1)
            StickOnLruChain_r(vnp,vcp);
        if (locktype == READ_LOCK)

diff --git a/src/vol/vnode.h b/src/vol/vnode.h
index 5477444..360c922 100644 (file)
--- a/src/vol/vnode.h
+++ b/src/vol/vnode.h
@@ -138,7 +138,7 @@ typedef struct Vnode {
     struct Volume
                *volumePtr;     /* Pointer to the volume containing this file*/
     byte       nUsers;         /* Number of lwp's who have done a VGetVnode */
-    bit16      cacheCheck;     /* Must equal the value in the volume Header
+    bit32      cacheCheck;     /* Must equal the value in the volume Header
                                   for the cache entry to be valid */
     struct     Lock lock;      /* Internal lock */
 #ifdef AFS_PTHREAD_ENV

diff --git a/src/vol/volume.c b/src/vol/volume.c
index db5da58..9f825bf 100644 (file)
--- a/src/vol/volume.c
+++ b/src/vol/volume.c
@@ -709,6 +709,9 @@ private Volume *attach2(ec, path, header, partp, isbusy)
     IH_INIT(vp->linkHandle, partp->device, header->parent,
                   header->linkTable);
     vp->cacheCheck = ++VolumeCacheCheck;
+    /* just in case this ever rolls over */
+    if (!vp->cacheCheck) 
+       vp->cacheCheck = ++VolumeCacheCheck;
     vp->shuttingDown = 0;
     vp->goingOffline = 0;
     vp->nUsers = 1;

diff --git a/src/vol/volume.h b/src/vol/volume.h
index f1dcc49..9b6adbd 100644 (file)
--- a/src/vol/volume.h
+++ b/src/vol/volume.h
@@ -310,7 +310,7 @@ typedef struct Volume {
                                   Added to vnode number for hash table index */
     byte       shuttingDown;   /* This volume is going to be detached */
     byte       goingOffline;   /* This volume is going offline */
-    bit16      cacheCheck;     /* Online sequence number to be used to invalidate vnode cache entries
+    bit32      cacheCheck;     /* Online sequence number to be used to invalidate vnode cache entries
                                   that stayed around while a volume was offline */
     short      nUsers;         /* Number of users of this volume header */
     byte       needsPutBack;   /* For a volume utility, this flag is set if we need