Re: sendfile from 9p fs into af_alg

From	Al Viro <viro@ZenIV.linux.org.uk>
Newsgroups	linux.kernel
Subject	Re: sendfile from 9p fs into af_alg
Date	2016-11-23 17:00 +0100
Message-ID	<sGI7M-6KY-17@gated-at.bofh.it> (permalink)
References	<sGwT0-7XV-1@gated-at.bofh.it> <sGxFn-8vk-11@gated-at.bofh.it> <sGxP3-6N-3@gated-at.bofh.it> <sGz4t-1dH-11@gated-at.bofh.it> <sGBzk-2Bt-15@gated-at.bofh.it>
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On Wed, Nov 23, 2016 at 12:58:11AM -0800, Alexei Starovoitov wrote:

> if I read it correctly 9p actually responded with 8192 bytes of requests...
> whereas the file size was 9624.
> For large file sizes (in megabytes) the difference between what
> sendfile is reporting and actual file size can be 3x.
> In the small file case (like above dump) it looks rounded to page size for some reason.

OK, I think I see one bug in there; could you check if this gets it back to
normal?

diff --git a/fs/splice.c b/fs/splice.c
index dcaf185..5a7750b 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) {

Thread

sendfile from 9p fs into af_alg Alexei Starovoitov <alexei.starovoitov@gmail.com> - 2016-11-23 05:00 +0100
  Re: sendfile from 9p fs into af_alg Al Viro <viro@ZenIV.linux.org.uk> - 2016-11-23 05:50 +0100
    Re: sendfile from 9p fs into af_alg Alexei Starovoitov <alexei.starovoitov@gmail.com> - 2016-11-23 06:00 +0100
      Re: sendfile from 9p fs into af_alg Al Viro <viro@ZenIV.linux.org.uk> - 2016-11-23 07:20 +0100
        Re: sendfile from 9p fs into af_alg Alexei Starovoitov <alexei.starovoitov@gmail.com> - 2016-11-23 10:00 +0100
          Re: sendfile from 9p fs into af_alg Al Viro <viro@ZenIV.linux.org.uk> - 2016-11-23 17:00 +0100
            Re: sendfile from 9p fs into af_alg Alexei Starovoitov <alexei.starovoitov@gmail.com> - 2016-11-23 17:40 +0100

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