Windows: after dir enum adjust dir scache LRU

During a directory enumeration the directory scache object
is reference counted so it can't be recycled.  However, if
there are more directory entries than the maximum number
of cached scache objects the directory scache object will
end up being the next object to be recycled after the refcount
is dropped.  Since the directory is clearly a hot object, before
dropping the reference, adjust the scache LRU position so that
it is the last object to be recycled.

Fix the variable name for the directory scache to be 'dscp'
for consistency.

Change-Id: Ia2089fb9b47dab77abc0911ab009e5aed75ed848
Reviewed-on: http://gerrit.openafs.org/5158
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
Tested-by: Jeffrey Altman <jaltman@openafs.org>

diff --git a/src/WINNT/afsd/cm_btree.c b/src/WINNT/afsd/cm_btree.c
index c916fb50e92dbe222089a4ca362ac107d66a88c4..212ef41859a6804479f9a8409858609c32b47df1 100644 (file)
--- a/src/WINNT/afsd/cm_btree.c
+++ b/src/WINNT/afsd/cm_btree.c
@@ -2175,7 +2175,7 @@ cm_BPlusEnumAlloc(afs_uint32 entries)
 }
 
 long
-cm_BPlusDirEnumerate(cm_scache_t *scp, cm_user_t *userp, cm_req_t *reqp,
+cm_BPlusDirEnumerate(cm_scache_t *dscp, cm_user_t *userp, cm_req_t *reqp,
                      afs_uint32 locked, clientchar_t * maskp,
                      afs_uint32 fetchStatus, cm_direnum_t **enumpp)
 {
@@ -2190,23 +2190,23 @@ cm_BPlusDirEnumerate(cm_scache_t *scp, cm_user_t *userp, cm_req_t *reqp,
 
     /* Read lock the bplus tree so the data can't change */
     if (!locked)
-       lock_ObtainRead(&scp->dirlock);
+       lock_ObtainRead(&dscp->dirlock);
 
     /*
-     * Hold a reference to the directory so that it wont' be
+     * Hold a reference to the directory so that it won't be
      * recycled while the enumeration is active.
      */
-    cm_HoldSCache(scp);
+    cm_HoldSCache(dscp);
     cm_HoldUser(userp);
 
-    if (scp->dirBplus == NULL) {
+    if (dscp->dirBplus == NULL) {
        osi_Log0(afsd_logp, "cm_BPlusDirEnumerate No BPlus Tree");
         rc = CM_ERROR_WOULDBLOCK;
        goto done;
     }
 
     /* Compute the number of entries */
-    for (count = 0, leafNode = getleaf(scp->dirBplus); leafNode; leafNode = nextLeafNode) {
+    for (count = 0, leafNode = getleaf(dscp->dirBplus); leafNode; leafNode = nextLeafNode) {
 
        for ( slot = 1, numentries = numentries(leafNode); slot <= numentries; slot++) {
            firstDataNode = getnode(leafNode, slot);
@@ -2244,7 +2244,7 @@ cm_BPlusDirEnumerate(cm_scache_t *scp, cm_user_t *userp, cm_req_t *reqp,
     }
 
     /* Copy the name and fid for each cname entry into the enumeration */
-    for (count = 0, leafNode = getleaf(scp->dirBplus); leafNode; leafNode = nextLeafNode) {
+    for (count = 0, leafNode = getleaf(dscp->dirBplus); leafNode; leafNode = nextLeafNode) {
 
        for ( slot = 1, numentries = numentries(leafNode); slot <= numentries; slot++) {
            firstDataNode = getnode(leafNode, slot);
@@ -2298,21 +2298,28 @@ cm_BPlusDirEnumerate(cm_scache_t *scp, cm_user_t *userp, cm_req_t *reqp,
        nextLeafNode = getnextnode(leafNode);
     }
 
-    enump->dscp = scp;
+    enump->dscp = dscp;
     enump->userp = userp;
     enump->reqFlags = reqp->flags;
     enump->fetchStatus = fetchStatus;
 
   done:
     if (!locked)
-       lock_ReleaseRead(&scp->dirlock);
+       lock_ReleaseRead(&dscp->dirlock);
 
     /* if we failed, cleanup any mess */
     if (rc != 0) {
        osi_Log0(afsd_logp, "cm_BPlusDirEnumerate rc != 0");
 
-        /* release the directory because we failed to generate an enumeration object */
-        cm_ReleaseSCache(scp);
+        /*
+         * release the directory because we failed to generate an enumeration object.
+         * adjust the directory position in the queue to ensure it doesn't get pushed
+         * out by the allocation of a large number of cm_scache objects.
+         */
+        lock_ObtainWrite(&cm_scacheLock);
+        cm_AdjustScacheLRU(dscp);
+        cm_ReleaseSCacheNoLock(dscp);
+        lock_ReleaseWrite(&cm_scacheLock);
         cm_ReleaseUser(userp);
         if (enump) {
            for ( count = 0; count < enump->count && enump->entry[count].name; count++ ) {
@@ -2510,8 +2517,16 @@ cm_BPlusDirFreeEnumeration(cm_direnum_t *enump)
     osi_Log0(afsd_logp, "cm_BPlusDirFreeEnumeration");
 
     if (enump) {
-        /* Release the directory object */
-        cm_ReleaseSCache(enump->dscp);
+        /*
+         * Release the directory object but first adjust its position
+         * in the LRU queue to ensure that it does not get stuck at the
+         * end due to the allocation of a large number of cm_scache
+         * entries in the directory.
+         */
+        lock_ObtainWrite(&cm_scacheLock);
+        cm_AdjustScacheLRU(enump->dscp);
+        cm_ReleaseSCacheNoLock(enump->dscp);
+        lock_ReleaseWrite(&cm_scacheLock);
         cm_ReleaseUser(enump->userp);
 
        for ( count = 0; count < enump->count && enump->entry[count].name; count++ ) {