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Date: Sat, 31 Aug 2019 08:54:46 +0800
From: Gao Xiang <gaoxiang25@huawei.com>
To: Christoph Hellwig <hch@infradead.org>
Subject: Re: [PATCH v6 03/24] erofs: add super block operations
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 <linux-erofs-bounces+linux-erofs=archiver.kernel.org@lists.ozlabs.org>

Hi Christoph,

On Sat, Aug 31, 2019 at 01:15:10AM +0800, Gao Xiang wrote:

[]

> > 
> > > > > +	/* be careful RCU symlink path (see ext4_inode_info->i_data)! */
> > > > > +	if (is_inode_fast_symlink(inode))
> > > > > +		kfree(inode->i_link);
> > > > 
> > > > is_inode_fast_symlink only shows up in a later patch.  And really
> > > > obsfucates the check here in the only caller as you can just do an
> > > > unconditional kfree here - i_link will be NULL except for the case
> > > > where you explicitly set it.
> > > 
> > > I cannot fully understand your point (sorry about my English),
> > > I will reply you about this later.
> > 
> > With that I mean that you should:
> > 
> >  1) remove is_inode_fast_symlink and just opencode it in the few places
> >     using it
> >  2) remove the check in this place entirely as it is not needed

Add some words about this suggestion since I'm addressing this place, it
seems it could not (or I am not sure at least) be freed unconditionally

	union {
		struct pipe_inode_info	*i_pipe;
		struct block_device	*i_bdev;
		struct cdev		*i_cdev;
		char			*i_link;
		unsigned		i_dir_seq;
	};

while I saw what shmem did, it seems that they handle as follows:
3636 static void shmem_free_in_core_inode(struct inode *inode)
3637 {
3638         if (S_ISLNK(inode->i_mode))
3639                 kfree(inode->i_link);
3640         kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
3641 }

I think that would be some check on it to get it is a symlink (for
i_dir_seq it seems unsafe).... I think the original check is ok but
I will opencode it instead.

Thanks,
Gao Xiang