Date: Wed, 09 May 2012 04:58:34 -0400 (EDT)
From: Zhouping Liu <zliu@redhat.com>
To: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org
Subject: mm: move_pages syscall can't return ENOENT when pages are not present
Message-ID: <85e08d38-234a-4bc6-8c4f-6c92b50dc9b1@zmail13.collab.prod.int.phx2.redhat.com>
In-Reply-To: <50e8b720-2459-4cf4-bfbd-fcc4cd408249@zmail13.collab.prod.int.phx2.redhat.com>
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hi, all

Recently, I found an error in move_pages syscall:

depending on move_pages(2), when page is not present,
it should fail with ENOENT, in fact, it's ok without
any errno.

the following reproducer can easily reproduce
the issue, suggest you get more details by strace.
inside reproducer, I try to move a non-exist page from
node 1 to node 0.

I have tested it on the latest kernel 3.4-rc5 with 2 and 4 numa nodes.
[zliu@ZhoupingLiu ~]$ gcc -o reproducer reproducer.c -lnuma
[zliu@ZhoupingLiu ~]$ ./reproducer 
from_node is 1, to_node is 0
ERROR: move_pages expected FAIL.

I'm not in mail list, please CC me.

/*
 * Copyright (C) 2012  Red Hat, Inc.
 *
 * This work is licensed under the terms of the GNU GPL, version 2. See
 * the COPYING file in the top-level directory.
 *
 * Compiled: gcc -o reproducer reproducer.c -lnuma
 * Description:
 * it's designed to check move_pages syscall, when
 * page is not present, it should fail with ENOENT.
 */

#include <sys/mman.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <numa.h>
#include <numaif.h>

#define TEST_PAGES 4

int main(int argc, char **argv)
{
	void *pages[TEST_PAGES];
	int onepage;
	int nodes[TEST_PAGES];
	int status, ret;
	int i, from_node = 1, to_node = 0;

	onepage = getpagesize();

	for (i = 0; i < TEST_PAGES - 1; i++) {
		pages[i] = numa_alloc_onnode(onepage, from_node);
		nodes[i] = to_node;
	}

	nodes[TEST_PAGES - 1] = to_node;

	/*
	 * the follow page is not available, also not aligned,
	 * depend on move_pages(2), it can't be moved, and should
	 * return ENOENT errno.
	 */
	pages[TEST_PAGES - 1] = pages[TEST_PAGES - 2] - onepage * 4 + 1;

	printf("from_node is %u, to_node is %u\n", from_node, to_node);
	ret = move_pages(0, TEST_PAGES, pages, nodes, &status, MPOL_MF_MOVE);
	if (ret == -1) {
		if (errno != ENOENT)
			perror("move_pages expected ENOENT errno, but it's");
		else
			printf("Succeed\n");
	} else {
		printf("ERROR: move_pages expected FAIL.\n");
	}

	for (i = 0; i < TEST_PAGES; i++)
		numa_free(pages[i], onepage);

	return 0;
}

-- 
Thanks,
Zhouping
--
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