From: Al Viro <viro@zeniv.linux.org.uk>
Date: Sun, 27 Nov 2016 01:05:42 +0000 (-0500)
Subject: fix default_file_splice_read()
X-Git-Url: http://git.cdn.openwrt.org/?a=commitdiff_plain;h=8e54cadab447dae779f80f79c87cbeaea9594f60;p=openwrt%2Fstaging%2Fblogic.git

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>
---

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) {