fix default_file_splice_read()

Botched calculation of number of pages.  As the result,
we were dropping pieces when doing splice to pipe from
e.g. 9p.

Reported-by: Alexei Starovoitov <ast@kernel.org>
Tested-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 2 insertions, 1 deletions

diff --git a/fs/splice.c b/fs/splice.c
index dcaf185a5731..5a7750bd2eea 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -408,7 +408,8 @@ static ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
         if (res <= 0)
                 return -ENOMEM;
 
-        nr_pages = res / PAGE_SIZE;
+        BUG_ON(dummy);
+        nr_pages = DIV_ROUND_UP(res, PAGE_SIZE);
 
         vec = __vec;
         if (nr_pages > PIPE_DEF_BUFFERS) {