Re: [PATCH 6/9] f2fs: zstd: Switch to the zstd-1.4.6 API

[Chao Yu]

On 2020/9/18 10:56, Eric Biggers wrote:
> On Fri, Sep 18, 2020 at 09:47:32AM +0800, Chao Yu wrote:
> > Ah, I got it.
> >
> > Step of enabling compressed inode is not correct, we should touch an empty
> > file, and then use 'chattr +c' on that file to enable compression, otherwise
> > the race condition could be complicated to handle. So we need below diff to
> > disallow setting compression flag on an non-empty file:
> >
> > diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> > index 8a422400e824..b462db7898fd 100644
> > --- a/fs/f2fs/file.c
> > +++ b/fs/f2fs/file.c
> > @@ -1836,6 +1836,8 @@ static int f2fs_setflags_common(struct inode *inode, u32 iflags, u32 mask)
> >   		if (iflags & F2FS_COMPR_FL) {
> >   			if (!f2fs_may_compress(inode))
> >   				return -EINVAL;
> > +			if (get_dirty_pages(inode) || fi->i_compr_blocks)
> > +				return  -EINVAL;
> >
> >   			set_compress_context(inode);
> >   		}
>
> Why not:
>
> 	if (inode->i_size)
> 		return -EINVAL;

Yeah, I noticed that after replying this email, I've prepared the new patch
which including the i_size check.

Thanks for noticing this.

Thanks,

> .