* FlushAndRemoveAllPages() cannot call WriteModified(), as it must be called

with the VMCache lock held, and WriteModified() locks itself.
* Added an assertion that the lock is held when calling that method.
* This fixes a KDL as soon as you would have used O_NOCACHE with a file that
  had already some pages read in.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@26864 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/system/kernel/vm/vm_cache.cpp

@@ -796,14 +796,17 @@ VMCache::Resize(off_t newSize)
 }
 
 
+/*!	You have to call this function with the VMCache lock held. */
 status_t
 VMCache::FlushAndRemoveAllPages()
 {
+	ASSERT_LOCKED_MUTEX(&fLock);
+
 	while (page_count > 0) {
 		// write back modified pages
-		status_t error = WriteModified();
-		if (error != B_OK)
-			return error;
+		status_t status = vm_page_write_modified_pages(this);
+		if (status != B_OK)
+			return status;
 
 		// remove pages
 		for (VMCachePagesTree::Iterator it = pages.GetIterator();