[PATCH] restore lru_cache_del() in truncate_complete_page

I removed the PF_INVALIDATE debug check from buffercache
leaks, too.  It's non-functional - the flag should have been
set across truncate_inode_pages(), not invalidate_inode_pages().

fs/buffer.c

@@ -448,9 +448,7 @@ void invalidate_bdev(struct block_device *bdev, int destroy_dirty_buffers)
 	 * We really want to use invalidate_inode_pages2() for
 	 * that, but not until that's cleaned up.
 	 */
-	current->flags |= PF_INVALIDATE;
 	invalidate_inode_pages(bdev->bd_inode);
-	current->flags &= ~PF_INVALIDATE;
 }
 
 void __invalidate_buffers(kdev_t dev, int destroy_dirty_buffers)

include/linux/sched.h

@@ -393,7 +393,7 @@ do { if (atomic_dec_and_test(&(tsk)->usage)) __put_task_struct(tsk); } while(0)
 #define PF_FREEZE	0x00010000	/* this task should be frozen for suspend */
 #define PF_IOTHREAD	0x00020000	/* this thread is needed for doing I/O to swap */
 #define PF_FROZEN	0x00040000	/* frozen for system suspend */
-#define PF_INVALIDATE	0x00080000	/* debug: unmounting an fs. killme. */
+
 /*
  * Ptrace flags
  */

mm/filemap.c

@@ -173,17 +173,16 @@ static inline void truncate_partial_page(struct page *page, unsigned partial)
 }
 
 /*
- * AKPM: the PagePrivate test here seems a bit bogus.  It bypasses the
- * mapping's ->invalidatepage, which may still want to be called.
+ * If truncate can remove the fs-private metadata from the page, it
+ * removes the page from the LRU immediately.  This because some other thread
+ * of control (eg, sendfile) may have a reference to the page.  But dropping
+ * the final reference to an LRU page in interrupt context is illegal - it may
+ * deadlock over pagemap_lru_lock.
  */
 static void truncate_complete_page(struct page *page)
 {
-	/* Drop fs-specific data so the page might become freeable. */
-	if (PagePrivate(page) && !do_invalidatepage(page, 0)) {
-		if (current->flags & PF_INVALIDATE)
-			printk("%s: buffer heads were leaked\n",
-				current->comm);
-	}
+	if (!PagePrivate(page) || do_invalidatepage(page, 0))
+		lru_cache_del(page);
 
 	ClearPageDirty(page);
 	ClearPageUptodate(page);