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Date: Wed, 09 May 2012 22:56:47 +0800
From: Wanlong Gao <gaowanlong@...fujitsu.com>
To: Zhouping Liu <zliu@...hat.com>
CC: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
LTP List <ltp-list@...ts.sourceforge.net>,
Xiaotian Feng <xtfeng@...il.com>, Brice.Goglin@...ia.fr
Subject: Re: mm: move_pages syscall can't return ENOENT when pages are not
present
On 05/09/2012 09:33 PM, Zhouping Liu wrote:
>
>
> ----- Original Message -----
>> From: "Wanlong Gao" <gaowanlong@...fujitsu.com>
>> To: "Xiaotian Feng" <xtfeng@...il.com>
>> Cc: "Zhouping Liu" <zliu@...hat.com>, linux-mm@...ck.org, linux-kernel@...r.kernel.org, "LTP List"
>> <ltp-list@...ts.sourceforge.net>
>> Sent: Wednesday, May 9, 2012 8:50:07 PM
>> Subject: Re: mm: move_pages syscall can't return ENOENT when pages are not present
>>
>> On 05/09/2012 05:28 PM, Xiaotian Feng wrote:
>>
>>> On Wed, May 9, 2012 at 4:58 PM, Zhouping Liu <zliu@...hat.com>
>>> wrote:
>>>> 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@...upingLiu ~]$ gcc -o reproducer reproducer.c -lnuma
>>>> [zliu@...upingLiu ~]$ ./reproducer
>>>> from_node is 1, to_node is 0
>>>> ERROR: move_pages expected FAIL.
>>>>
>>>
>>> " If nodes is not NULL, move_pages returns the number of valid
>>> migration requests which could not currently be performed.
>>> Otherwise
>>> it returns 0."
>>
>>
>> FYI, actually,
>> commit e78bbfa8262424417a29349a8064a535053912b9
>> Author: Brice Goglin <Brice.Goglin@...ia.fr>
>> Date: Sat Oct 18 20:27:15 2008 -0700
>>
>> mm: stop returning -ENOENT from sys_move_pages() if nothing got
>> migrated
>
> maybe you missed my thought :(
> if I'm wrong, please correct me.
>
> IMO, the issue is different with the patch.
> apparently, in the case(reproducer), I tried to move 4 pages from node 1 to node 0,
> and the 4th page is an invalid page(absent and not aligned)
> pages[TEST_PAGES - 1] = pages[TEST_PAGES - 2] - onepage * 4 + 1;
> but the reproducer passed with any errors, I think it's not common.
>
> in the case, numa_free() return EINVAL, but we can't catch the err:
So, as Brice said, if you want to catch error, you should check your status array after
doing move_pages.
Thanks,
Wanlong Gao
> [root@...upingLiu zliu]# strace ./reproducer
> ...
> move_pages(0, 4, {0x7f029c459000, 0x7f029c458000, 0x7f029c457000, 0x7f029c453001}, {0, 0, 0, 0}, {0xfffffffe, 0xfffffffe, 0xfffffffe, 0xfffffff2}, MPOL_MF_MOVE) = 0
> write(1, "ERROR: move_pages expected FAIL."..., 33ERROR: move_pages expected FAIL.
> ) = 33
> munmap(0x7f029c459000, 4096) = 0
> munmap(0x7f029c458000, 4096) = 0
> munmap(0x7f029c457000, 4096) = 0
> munmap(0x7f029c453001, 4096) = -1 EINVAL (Invalid argument)
> ...
>
> so I suggest we check pages' validity before move pages, if they are invalid, it should return
> relevant error number to userspace, maybe it's other errno, not ENOENT, correct?
>
> I'm trying to make a patch, but I'm a newer to the part :(
>
>>
>> this commit changed the behaviour.
>>
>> And the LTP has fixed to be consistent with this,
>> https://github.com/linux-test-project/ltp/commit/338299da1ff27c7815183c1b07eb91e705f117ce
>>
>>
>> Thanks,
>> Wanlong Gao
>>
>>>
>>>> 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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>>
>>
>>
>
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