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

[Weichao Guo]

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@xxxxxxxx <huangjianan@xxxxxxxx>
> > > > > > > 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@xxxxxxxx>
> > > > > > >        Signed-off-by: Guo Weichao <guoweichao@xxxxxxxx>
> > > > > > >        Reviewed-by: Chao Yu <yuchao0@xxxxxxxxxx>
> > > > > > >        Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
> > > > > > 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();
> > .