dirty page table flush was pinning pages, then asserting they were not pinned; updated page writeback api to allow correct usage

src/stasis/bufferManager.c

@@ -161,7 +161,7 @@ Page * (*loadPageImpl)(int xid, pageid_t pageid, pagetype_t type) = 0;
 Page * (*loadUninitPageImpl)(int xid, pageid_t pageid) = 0;
 Page * (*getCachedPageImpl)(int xid, pageid_t pageid) = 0;
 void   (*releasePageImpl)(Page * p) = 0;
-int (*writeBackPage)(Page * p) = 0;
+int (*writeBackPage)(pageid_t page) = 0;
 void (*forcePages)() = 0;
 void (*forcePageRange)(pageid_t start, pageid_t stop) = 0;
 void   (*stasis_buffer_manager_close)()  = 0;

src/stasis/bufferManager/bufferHash.c

@@ -90,21 +90,24 @@ inline static void checkPageState(Page * p) { }
 
 #endif
 
-inline static int tryToWriteBackPage(Page * p) {
+inline static int tryToWriteBackPage(pageid_t page) {
+
+  Page * p = lhfind(cachedPages, &page, sizeof(page));
+
+  if(!p) { return ENOENT; }
+
+  assert(p->id == page);
 
   if(*pagePendingPtr(p) || *pagePinCountPtr(p)) {
-    return 0;
+    return EBUSY;
   }
 
   DEBUG("Write(%ld)\n", (long)victim->id);
   page_handle->write(page_handle, p);  /// XXX pageCleanup and pageFlushed might be heavyweight.
-  stasis_page_cleanup(p);
 
   assert(!p->dirty);
-  // Make sure that no one mistakenly thinks this is still a live copy.
-  p->id = -1;
 
-  return 1;
+  return 0;
 }
 /** You need to hold mut before calling this.
 
@@ -126,11 +129,17 @@ inline static Page * writeBackOnePage() {
   checkPageState(victim);
 
   lru->remove(lru, victim);
+
+  int err= tryToWriteBackPage(victim->id);
+  assert(!err);
+
   Page * old = LH_ENTRY(remove)(cachedPages, &(victim->id), sizeof(victim->id));
   assert(old == victim);
 
-  int couldWriteBackPage = tryToWriteBackPage(victim);
+  stasis_page_cleanup(victim);
-  assert(couldWriteBackPage);
+  // Make sure that no one mistakenly thinks this is still a live copy.
+  victim->id = -1;
+
 
 #ifdef LATCH_SANITY_CHECKING
   // We can release the lock since we just grabbed it to see if
@@ -369,8 +378,8 @@ static void bhReleasePage(Page * p) {
 #endif
   pthread_mutex_unlock(&mut);
 }
-static int bhWriteBackPage(Page * p) {
+static int bhWriteBackPage(pageid_t pageid) {
-  return tryToWriteBackPage(p);
+  return tryToWriteBackPage(pageid);
 }
 static void bhForcePages() {
   page_handle->force_file(page_handle);

src/stasis/bufferManager/legacy/legacyBufferManager.c

@@ -31,9 +31,12 @@ static stasis_page_handle_t * page_handle;
 
 static stasis_buffer_pool_t * stasis_buffer_pool;
 
-static int pageWrite_legacyWrapper(Page * p) {
+static int pageWrite_legacyWrapper(pageid_t pageid) {
+  Page * p = loadPage(-1, pageid);
+  // XXX this is unsafe; the page could be pinned!
   page_handle->write(page_handle,p);
-  return 1; // XXX probably unsafe.
+  releasePage(p);
+  return 0;
 }
 static void forcePageFile_legacyWrapper() {
   page_handle->force_file(page_handle);

src/stasis/bufferManager/pageArray.c

@@ -47,7 +47,7 @@ static void paReleasePage(Page * p) {
   stasis_dirty_page_table_set_clean(stasis_runtime_dirty_page_table(), p);
 }
 
-static int paWriteBackPage(Page * p) { return 1;  /* no-op */ }
+static int paWriteBackPage(pageid_t p) { return 0;  /* no-op */ }
 static void paForcePages() { /* no-op */ }
 static void paForcePageRange(pageid_t start, pageid_t stop) { /* no-op */ }
 

src/stasis/dirtyPageTable.c

@@ -106,12 +106,8 @@ void stasis_dirty_page_table_flush_range(stasis_dirty_page_table_t * dirtyPages,
   pthread_mutex_unlock(&dirtyPages->mutex);
 
   for(pageid_t i = 0; i < n; i++) {
-    Page * p = getCachedPage(-1, staleDirtyPages[i]);
+      int err = writeBackPage(staleDirtyPages[i]);
-    if(p) {
+      if(stop && (err == EBUSY)) { abort(); /*api violation!*/ }
-      int succ = writeBackPage(p);
-      if(stop && (!succ)) { abort(); /*api violation!*/ }
-      releasePage(p);
-    }
   }
   free(staleDirtyPages);
   forcePageRange(start*PAGE_SIZE,stop*PAGE_SIZE);

stasis/bufferManager.h

@@ -138,8 +138,10 @@ extern void   (*releasePageImpl)(Page * p);
     (Not all buffer managers support synchronous writes to stable
      storage.  For compatibility, such buffer managers should ignore
      this call.)
+
+     @return 0 on success, ENOENT if the page is not in cache, and EBUSY if the page is pinned.
 */
-extern int (*writeBackPage)(Page * p);
+extern int (*writeBackPage)(pageid_t p);
 /**
     Force any written back pages to disk.
 

test/stasis/check_dirtyPageTable.c

@@ -130,7 +130,7 @@ Suite * check_suite(void) {
 
   /* Sub tests are added, one per line, here */
   tcase_add_test(tc, dirtyPageTable_randomTest);
-//  tcase_add_test(tc, dirtyPageTable_threadTest);
+  tcase_add_test(tc, dirtyPageTable_threadTest);
 
   /* --------------------------------------------- */