linux-kernel - Re: [PATCH v2 1/3] mm/shmem: check return value of shmem_init

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Date:   Mon, 6 Jun 2022 03:08:58 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Chen Wandun <chenwandun@...wei.com>
Cc:     hughd@...gle.com, akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, david@...hat.com,
        wangkefeng.wang@...wei.com
Subject: Re: [PATCH v2 1/3] mm/shmem: check return value of
 shmem_init_inodecache

On Mon, Jun 06, 2022 at 09:34:13AM +0800, Chen Wandun wrote:
> On 2022/6/5 19:49, Matthew Wilcox wrote:
> > On Sun, Jun 05, 2022 at 11:55:55AM +0800, Chen Wandun wrote:
> > > It will result in null pointer access if shmem_init_inodecache fail,
> > > so check return value of shmem_init_inodecache
> > You ignored my suggestion from v1.  Here, let me write it out for you.
> Hi Matthew,
> I didn't ignore your suggestion,  some explanation is needed, sorry for
> that.
> 
> In V1, Kefeng point:
> "kmem_cache_create return a pointer to the cache on success, NULL on
> failure,
> so error = -ENOMEM; is right :)"
> 
> so, I look some similar code such as init_inodecache in kinds of file
> system,  they all
> return -ENOMEM on failure, so is it OK to return -ENOMEM on failure :)
> 
> Besides,  kmem_cache_create return NULL on failure, maybe returning error
> code
> on failure is more proper, but it is another job.

I literally wrote out what I think you should do instead.  Stop arguing.

> > +static int shmem_init_inodecache(void)
> >   {
> >    	shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
> >    				sizeof(struct shmem_inode_info),
> >    				0, SLAB_PANIC|SLAB_ACCOUNT, shmem_init_inode);
> > +	if (!shmem_inode_cachep)
> > +		return -ENOMEM;
> > +	return 0;
> >   }
> > 
> > ...
> > 
> > +	error = shmem_init_inodecache();
> > +	if (error)
> > +		goto out2;
> > 
> > 
> > .
>