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

[Huang Jianan <huangjianan@oppo.com>]

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@oppo.com <huangjianan@oppo.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@oppo.com>
>>>>       Signed-off-by: Guo Weichao <guoweichao@oppo.com>
>>>>       Reviewed-by: Chao Yu <yuchao0@huawei.com>
>>>>       Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.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()?