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

Eric Biggers
2020-09-18T02:56:50Z

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;