Windows: optimize buf_FlushCleanPages

If the pages to be flushed are from a readonly or backup volume
they can't be dirty.  In this case there is no need to stabilize
the pages before they are locked and recycled.

Stablilization is performed on the cm_scache_t object so do not
stabilize and unstablize for each cm_buf_t object.

LICENSE MIT

Change-Id: I6fa86cf0a33dc9f45d77911909e799c0fc6510cf
Reviewed-on: http://gerrit.openafs.org/2518
Tested-by: Jeffrey Altman <jaltman@openafs.org>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>

diff --git a/src/WINNT/afsd/cm_buf.c b/src/WINNT/afsd/cm_buf.c
index 3920844f79a6862ad19e1fda621bf15f44726af0..af7651b5cd6ed570748435251408f983f543b7ad 100644 (file)
--- a/src/WINNT/afsd/cm_buf.c
+++ b/src/WINNT/afsd/cm_buf.c
@@ -1655,6 +1655,7 @@ long buf_FlushCleanPages(cm_scache_t *scp, cm_user_t *userp, cm_req_t *reqp)
     cm_buf_t *nbp;
     int didRelease;
     afs_uint32 i;
+    afs_uint32 stable = 0;
 
     i = BUF_FILEHASH(&scp->fid);
 
@@ -1664,12 +1665,23 @@ long buf_FlushCleanPages(cm_scache_t *scp, cm_user_t *userp, cm_req_t *reqp)
     if (bp) 
         buf_HoldLocked(bp);
     lock_ReleaseRead(&buf_globalLock);
-    
+
     for (; bp; bp = nbp) {
         didRelease = 0;        /* haven't released this buffer yet */
 
         /* clean buffer synchronously */
         if (cm_FidCmp(&bp->fid, &scp->fid) == 0) {
+
+            /*
+             * if the object is not located on a read/write volume
+             * we must stabilize the object to ensure that buffer
+             * changes cannot occur while the flush is performed.
+             */
+            if (!stable && code == 0 && !(scp->flags & CM_SCACHEFLAG_RO)) {
+                code = (*cm_buf_opsp->Stabilizep)(scp, userp, reqp);
+                stable = (code == 0);
+            }
+
             lock_ObtainMutex(&bp->mx);
 
             /* start cleaning the buffer, and wait for it to finish */
@@ -1677,16 +1689,6 @@ long buf_FlushCleanPages(cm_scache_t *scp, cm_user_t *userp, cm_req_t *reqp)
             buf_WaitIO(scp, bp);
             lock_ReleaseMutex(&bp->mx);
 
-            /* 
-             * if the error for the previous buffer was BADFD
-             * then all buffers for the FID are bad.  Do not
-             * attempt to stabalize.
-             */
-            if (code != CM_ERROR_BADFD) {
-                code = (*cm_buf_opsp->Stabilizep)(scp, userp, reqp);
-                if (code && code != CM_ERROR_BADFD) 
-                    goto skip;
-            }
             if (code == CM_ERROR_BADFD) {
                 /* if the scp's FID is bad its because we received VNOVNODE 
                  * when attempting to FetchStatus before the write.  This
@@ -1701,6 +1703,8 @@ long buf_FlushCleanPages(cm_scache_t *scp, cm_user_t *userp, cm_req_t *reqp)
                 bp->dataVersion = CM_BUF_VERSION_BAD;  /* known bad */
                 bp->dirtyCounter++;
                 lock_ReleaseMutex(&bp->mx);
+            } else if (!stable && code) {
+                goto skip;
             }
 
             /* actually, we only know that buffer is clean if ref
@@ -1718,9 +1722,6 @@ long buf_FlushCleanPages(cm_scache_t *scp, cm_user_t *userp, cm_req_t *reqp)
                 }
                 lock_ReleaseWrite(&buf_globalLock);
             }
-
-           if (code == 0)
-               (*cm_buf_opsp->Unstabilizep)(scp, userp);
         }
 
       skip:
@@ -1734,6 +1735,9 @@ long buf_FlushCleanPages(cm_scache_t *scp, cm_user_t *userp, cm_req_t *reqp)
         }
     }  /* for loop over a bunch of buffers */
 
+    if (stable)
+        (*cm_buf_opsp->Unstabilizep)(scp, userp);
+
 #ifdef TESTING
     buf_ValidateBufQueues();
 #endif /* TESTING */