splice: fix bad unlock_page() in error case

If add_to_page_cache_lru() fails, the page will not be locked. But
splice jumps to an error path that does a page release and unlock,
causing a BUG() in unlock_page().

Fix this by adding one more label that just releases the page. This bug
was actually triggered on EL5 by gurudas pai <gurudas.pai@oracle.com>
using fio.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 2 deletions

diff --git a/fs/splice.c b/fs/splice.c
index 22496d2a73fa..0a0973218084 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -594,7 +594,7 @@ find_page:
                 ret = add_to_page_cache_lru(page, mapping, index,
                                             GFP_KERNEL);
                 if (unlikely(ret))
-                        goto out;
+                        goto out_release;
         }
 
         ret = mapping->a_ops->prepare_write(file, page, offset, offset+this_len);
@@ -650,8 +650,9 @@ find_page:
          */
         mark_page_accessed(page);
 out:
-        page_cache_release(page);
         unlock_page(page);
+out_release:
+        page_cache_release(page);
 out_ret:
         return ret;
 }