[BUG] LTP test case readahead01 fails after commit 63d0f0a3c7

[Wanlong Gao <gaowanlong@cn.fujitsu.com>]

Hi AKPM and folks,

LTP test readahead syscall return value like this:

=====================
static void test_invalid_fd(void)
{
	int fd[2];

	tst_resm(TINFO, "test_invalid_fd pipe");
	if (pipe(fd) < 0)
		tst_resm(TBROK | TERRNO, "Failed to create pipe");
	TEST(ltp_syscall(__NR_readahead, fd[0], 0, getpagesize()));
	check_ret(-1);
	check_errno(EINVAL);
	close(fd[0]);
	close(fd[1]);

	tst_resm(TINFO, "test_invalid_fd socket");
	fd[0] = socket(AF_INET, SOCK_STREAM, 0);
	if (fd[0] < 0)
		tst_resm(TBROK | TERRNO, "Failed to create socket");
	TEST(ltp_syscall(__NR_readahead, fd[0], 0, getpagesize()));
	check_ret(-1);
	check_errno(EINVAL);
	close(fd[0]);
}
====================================
FULL case code: https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/syscalls/readahead/readahead01.c


This case passed before the following kernel commit[1],
it means kernel will return -1 with errno=EINVAL. But after
this commit[1], kernel will return 0 here.

The different between before and after this commit[1] is that:
BEFORE:
=============
do_readahead():
if (!mapping || !mapping->a_ops || !mapping->a_ops->readpage)
	return EINVAL;
============

AFTER:
======================
do_readahead():
if (!mapping || !mapping->a_ops)
	return EINVAL;

And followed with:

force_page_cache_readahead():
if (unlikely(!mapping->a_ops->readpage && !mapping->a_ops->readpages))
		return -EINVAL;
=====================

I think you must know which is right?




Thanks,
Wanlong Gao



[1]:
commit 63d0f0a3c7e1281fd79268a8d988167eff607fb6
Author: Andrew Morton <akpm@linux-foundation.org>
Date:   Tue Nov 12 15:07:09 2013 -0800

    mm/readahead.c:do_readhead(): don't check for ->readpage
    
    The callee force_page_cache_readahead() already does this and unlike
    do_readahead(), force_page_cache_readahead() remembers to check for
    ->readpages() as well.
    
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/readahead.c b/mm/readahead.c
index e4ed041..5024183 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -569,7 +569,7 @@ static ssize_t
 do_readahead(struct address_space *mapping, struct file *filp,
             pgoff_t index, unsigned long nr)
 {
-       if (!mapping || !mapping->a_ops || !mapping->a_ops->readpage)
+       if (!mapping || !mapping->a_ops)
                return -EINVAL;
 
        force_page_cache_readahead(mapping, filp, index, nr);