linux-kernel - [PATCH] mm: adjust max read count in generic_file_buffered

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Message-Id: <20180719081726.3341-1-cgxu519@gmx.com>
Date:   Thu, 19 Jul 2018 16:17:26 +0800
From:   Chengguang Xu <cgxu519@....com>
To:     akpm@...ux-foundation.org, jack@...e.cz,
        mgorman@...hsingularity.net, jlayton@...hat.com,
        ak@...ux.intel.com, mawilcox@...rosoft.com,
        tim.c.chen@...ux.intel.com
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Chengguang Xu <cgxu519@....com>
Subject: [PATCH] mm: adjust max read count in generic_file_buffered_read()

When we try to truncate read count in generic_file_buffered_read(),
should deliver (sb->s_maxbytes - offset) as maximum count not
sb->s_maxbytes itself.

Signed-off-by: Chengguang Xu <cgxu519@....com>
---
 mm/filemap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index 52517f28e6f4..5c2d481d21cf 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2064,7 +2064,7 @@ static ssize_t generic_file_buffered_read(struct kiocb *iocb,
 
 	if (unlikely(*ppos >= inode->i_sb->s_maxbytes))
 		return 0;
-	iov_iter_truncate(iter, inode->i_sb->s_maxbytes);
+	iov_iter_truncate(iter, inode->i_sb->s_maxbytes - *ppos);
 
 	index = *ppos >> PAGE_SHIFT;
 	prev_index = ra->prev_pos >> PAGE_SHIFT;
-- 
2.17.1