linux-kernel - Re: [LTP] [f2fs] 02eb84b96b: ltp.swapon03.fail

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Date:   Tue, 23 Mar 2021 17:04:32 +0800
From:   Chao Yu <yuchao0@...wei.com>
To:     Jaegeuk Kim <jaegeuk@...nel.org>,
        Huang Jianan <huangjianan@...o.com>
CC:     Matthew Wilcox <willy@...radead.org>,
        Weichao Guo <guoweichao@...o.com>, <rpalethorpe@...e.de>,
        kernel test robot <oliver.sang@...el.com>, <lkp@...el.com>,
        Linux Memory Management List <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>, <lkp@...ts.01.org>,
        <ltp@...ts.linux.it>
Subject: Re: [LTP] [f2fs] 02eb84b96b: ltp.swapon03.fail

On 2021/3/11 4:49, Jaegeuk Kim wrote:
> On 03/10, Huang Jianan wrote:
>> Hi Richard,
>>
>> On 2021/3/9 12:01, Matthew Wilcox wrote:
>>> On Tue, Mar 09, 2021 at 10:23:35AM +0800, Weichao Guo wrote:
>>>> Hi Richard,
>>>>
>>>> On 2021/3/8 19:53, Richard Palethorpe wrote:
>>>>> Hello,
>>>>>
>>>>>> kern  :err   : [  187.461914] F2FS-fs (sda1): Swapfile does not align to section
>>>>>> commit 02eb84b96bc1b382dd138bf60724edbefe77b025
>>>>>> Author: huangjianan@...o.com <huangjianan@...o.com>
>>>>>> Date:   Mon Mar 1 12:58:44 2021 +0800
>>>>>>        f2fs: check if swapfile is section-alligned
>>>>>>        If the swapfile isn't created by pin and fallocate, it can't be
>>>>>>        guaranteed section-aligned, so it may be selected by f2fs gc. When
>>>>>>        gc_pin_file_threshold is reached, the address of swapfile may change,
>>>>>>        but won't be synchronized to swap_extent, so swap will write to wrong
>>>>>>        address, which will cause data corruption.
>>>>>>        Signed-off-by: Huang Jianan <huangjianan@...o.com>
>>>>>>        Signed-off-by: Guo Weichao <guoweichao@...o.com>
>>>>>>        Reviewed-by: Chao Yu <yuchao0@...wei.com>
>>>>>>        Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
>>>>> The test uses fallocate to preallocate the swap file and writes zeros to
>>>>> it. I'm not sure what pin refers to?
>>>> 'pin' refers to pinned file feature in F2FS, the LBA(Logical Block Address)
>>>> of a file is fixed after pinned. Without this operation before fallocate,
>>>> the LBA may not align with section(F2FS GC unit), some LBA of the file may
>>>> be changed by F2FS GC in some extreme cases.
>>>>
>>>> For this test case, how about pin the swap file before fallocate for F2FS as
>>>> following:
>>>>
>>>> ioctl(fd, F2FS_IOC_SET_PIN_FILE, true);
>>> No special ioctl should be needed.  f2fs_swap_activate() should pin the
>>> file, just like it converts inline inodes and disables compression.
>>
>> Now f2fs_swap_activate() will pin the file. The problem is that when
>> f2fs_swap_activate()
>>
>> is executed, the file has been created and may not be section-aligned.
>>
>> So I think it would be better to consider aligning the swapfile during
>> f2fs_swap_activate()?
> 
> Does it make sense to reallocate blocks like
> in f2fs_swap_activate(),
> 	set_inode_flag(inode, FI_PIN_FILE);
> 	truncate_pagecache(inode, 0);
> 	f2fs_truncate_blocks(inode, 0, true);

It will corrupt swap header info while relocating whole swapfile...

> 	expand_inode_data();
> .
>