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

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Message-ID: <cf28837a-9558-b00c-bca3-601a70b752ea@oppo.com>
Date:   Thu, 29 Apr 2021 21:08:42 +0800
From:   Weichao Guo <guoweichao@...o.com>
To:     Chao Yu <yuchao0@...wei.com>, Jaegeuk Kim <jaegeuk@...nel.org>,
        Huang Jianan <huangjianan@...o.com>
Cc:     Matthew Wilcox <willy@...radead.org>, 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 2021/3/23 17:04, Chao Yu wrote:
> 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...
How about back up the header page, and recover it after 
expand_inode_data() ?
>
>>     expand_inode_data();
>> .
>>