[PATCH] splice: fix bugs with stealing regular pipe pages

- Check that page has suitable count for stealing in the regular pipes.
- pipe_to_file() assumes that the page is locked on succesful steal, so
  do that in the pipe steal hook
- Missing unlock_page() in add_to_page_cache() failure.

Signed-off-by: Jens Axboe <axboe@suse.de>
diff --git a/fs/splice.c b/fs/splice.c
index a46ddd2..9df28d3 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -599,8 +599,10 @@
 			goto find_page;
 
 		page = buf->page;
-		if (add_to_page_cache(page, mapping, index, gfp_mask))
+		if (add_to_page_cache(page, mapping, index, gfp_mask)) {
+			unlock_page(page);
 			goto find_page;
+		}
 
 		if (!(buf->flags & PIPE_BUF_FLAG_LRU))
 			lru_cache_add(page);