linux-kernel - [PATCH] mm/filemap.c: fix criteria of calling iov_shorten() in generic_file_direct

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Message-ID: <51764857.5010808@cn.fujitsu.com>
Date:	Tue, 23 Apr 2013 16:37:43 +0800
From:	Gu Zheng <guz.fnst@...fujitsu.com>
To:	akpm@...ux-foundation.org
CC:	linux-mm@...ck.org, linux-kernel <linux-kernel@...r.kernel.org>,
	Al Viro <viro@...iv.linux.org.uk>, Jens <axboe@...nel.dk>
Subject: [PATCH] mm/filemap.c: fix criteria of calling iov_shorten() in generic_file_direct_write()

>From 35947e6535d92c54cf523470cc8811e8b5fee3e5 Mon Sep 17 00:00:00 2001
From: Gu Zheng <guz.fnst@...fujitsu.com>
Date: Tue, 23 Apr 2013 16:09:04 +0800
Subject: [PATCH] mm/filemap.c: fix criteria of calling iov_shorten() in generic_file_direct_write()

generic_file_direct_write() compares 'count'(the max count we actually can write)
with 'ocount'(the count we request to write) to see if there is need to call
iov_shorten() to reduce number of segments and the iovec's length. If the
'count' is equal or greater than 'ocount', there is no need to call iov_shorten()
indeed. So the judgement should be changed:
'if (count != ocount)' --> 'if (count < ocount)'

Signed-off-by: Gu Zheng <guz.fnst@...fujitsu.com>
---
 mm/filemap.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index e1979fd..c566b9c 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2183,7 +2183,7 @@ generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov,
 	size_t		write_len;
 	pgoff_t		end;
 
-	if (count != ocount)
+	if (count < ocount)
 		*nr_segs = iov_shorten((struct iovec *)iov, *nr_segs, count);
 
 	write_len = iov_length(iov, *nr_segs);
-- 
1.7.7

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