linux-kernel - Re: [f2fs-dev] [PATCH v5 2/2] f2fs: add F2FS_IOC_SET_COMPRESS

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Date:   Fri, 30 Oct 2020 10:46:16 +0900
From:   Daeho Jeong <daeho43@...il.com>
To:     Eric Biggers <ebiggers@...nel.org>
Cc:     Chao Yu <yuchao0@...wei.com>, linux-kernel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net, kernel-team@...roid.com,
        Daeho Jeong <daehojeong@...gle.com>
Subject: Re: [f2fs-dev] [PATCH v5 2/2] f2fs: add F2FS_IOC_SET_COMPRESS_OPTION ioctl

Chao, got it on f2fs_is_compress_algorithm_valid().
I also agree on Eric's opinion on that error value.

2020년 10월 30일 (금) 오전 12:54, Eric Biggers <ebiggers@...nel.org>님이 작성:
>
> On Thu, Oct 29, 2020 at 03:29:17PM +0800, Chao Yu wrote:
> > > +static int f2fs_ioc_set_compress_option(struct file *filp, unsigned long arg)
> > > +{
> > > +   struct inode *inode = file_inode(filp);
> > > +   struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
> > > +   struct f2fs_comp_option option;
> > > +   int ret = 0;
> > > +
> > > +   if (!f2fs_sb_has_compression(sbi))
> > > +           return -EOPNOTSUPP;
> > > +
> > > +   if (!(filp->f_mode & FMODE_WRITE))
> > > +           return -EBADF;
> > > +
> > > +   if (copy_from_user(&option, (struct f2fs_comp_option __user *)arg,
> > > +                           sizeof(option)))
> > > +           return -EFAULT;
> > > +
> > > +   if (!f2fs_compressed_file(inode) ||
> > > +                   option.log_cluster_size < MIN_COMPRESS_LOG_SIZE ||
> > > +                   option.log_cluster_size > MAX_COMPRESS_LOG_SIZE ||
> > > +                   option.algorithm >= COMPRESS_MAX)
> > > +           return -EINVAL;
> > > +
> > > +   file_start_write(filp);
> > > +   inode_lock(inode);
> > > +
> > > +   if (f2fs_is_mmap_file(inode) || get_dirty_pages(inode)) {
> > > +           ret = -EBUSY;
> > > +           goto out;
> > > +   }
> > > +
> > > +   if (inode->i_size != 0) {
> > > +           ret = -EFBIG;
> > > +           goto out;
> > > +   }
> >
> > Hmm...
> >
> > Shouldn't it be:
> >
> > if (algorithm >= COMPRESS_MAX) {
> >       ret = -ENOPKG;
> >       goto out;
> > }
> >
> > if (!f2fs_cops[algorithm])
> >       f2fs_warn(...);
>
> Note that my intent with recommending ENOPKG was for it to be returned in the
> !f2fs_cops[algorithm] case, similar to how opening an encrypted file when the
> encryption algorithm is recognized but not supported by the kernel returns
> ENOPKG.  For a truly unrecognized algorithm (algorithm >= COMPRESS_MAX), EINVAL
> would probably be more appropriate.  So if !f2fs_cops[algorithm] is now allowed,
> then ENOPKG should no longer be among the error codes this ioctl returns.
>
> - Eric