Re: [PATCH] nfsd: fail module init on reply cache init failure

[Peter Staubach <staubach@redhat.com>]

J. Bruce Fields wrote:
> If the reply cache initialization fails due to a kmalloc failure,
> currently we try to soldier on with a reduced (or nonexistant) reply
> cache.
>
> Better to just fail immediately: the failure is then much easier to
> understand and debug, and it could save us complexity in some later
> code.  (But actually, it doesn't help currently because the cache is
> also turned off in some odd failure cases; we should probably find a
> better way to handle those failure cases some day.)
>
> Fix some minor style problems while we're at it, and rename
> nfsd_cache_init() to remove the need for a comment describing it.
>
> Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
> ---
>  fs/nfsd/nfscache.c         |   28 +++++++++++++---------------
>  fs/nfsd/nfsctl.c           |   11 +++++++----
>  include/linux/nfsd/cache.h |    4 ++--
>  3 files changed, 22 insertions(+), 21 deletions(-)
>
> diff --git a/fs/nfsd/nfscache.c b/fs/nfsd/nfscache.c
> index 578f2c9..92cb5ae 100644
> --- a/fs/nfsd/nfscache.c
> +++ b/fs/nfsd/nfscache.c
> @@ -44,17 +44,18 @@ static int	nfsd_cache_append(struct svc_rqst *rqstp, struct kvec *vec);
>   */
>  static DEFINE_SPINLOCK(cache_lock);
>  
> -void
> -nfsd_cache_init(void)
> +int
> +nfsd_reply_cache_init(void)
>  {
>  	struct svc_cacherep	*rp;
>  	int			i;
>  
>  	INIT_LIST_HEAD(&lru_head);
>  	i = CACHESIZE;
> -	while(i) {
> +	while (i) {
>  		rp = kmalloc(sizeof(*rp), GFP_KERNEL);
> -		if (!rp) break;
> +		if (!rp)
> +			goto out_nomem;
>  		list_add(&rp->c_lru, &lru_head);
>  		rp->c_state = RC_UNUSED;
>  		rp->c_type = RC_NOCACHE;
> @@ -62,23 +63,20 @@ nfsd_cache_init(void)
>  		i--;
>  	}
>  
> -	if (i)
> -		printk (KERN_ERR "nfsd: cannot allocate all %d cache entries, only got %d\n",
> -			CACHESIZE, CACHESIZE-i);
> -
>  	hash_list = kcalloc (HASHSIZE, sizeof(struct hlist_head), GFP_KERNEL);
> -	if (!hash_list) {
> -		nfsd_cache_shutdown();
> -		printk (KERN_ERR "nfsd: cannot allocate %Zd bytes for hash list\n",
> -			HASHSIZE * sizeof(struct hlist_head));
> -		return;
> -	}
> +	if (!hash_list)
> +		goto out_nomem;
>  
>  	cache_disabled = 0;
> +	return 0;
> +out_nomem:
> +	printk(KERN_ERR "nfsd: failed to allocate reply cache\n");
>   

I was thinking that it might be nice to have something which
better explains what the ramifications of this failure might
be.  This explains _precisely_ what happened, but not what
will happen in the future.

Or can we get this documented in some fashion that admins
will know how to find and translate to what they need to
understand and do?

    Thanx...

       ps

> +	nfsd_reply_cache_shutdown();
> +	return -ENOMEM;
>  }
>  
>  void
> -nfsd_cache_shutdown(void)
> +nfsd_reply_cache_shutdown(void)
>  {
>  	struct svc_cacherep	*rp;
>  
> diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
> index ecf3779..2bfda9b 100644
> --- a/fs/nfsd/nfsctl.c
> +++ b/fs/nfsd/nfsctl.c
> @@ -683,7 +683,9 @@ static int __init init_nfsd(void)
>  	if (retval)
>  		return retval;
>  	nfsd_stat_init();	/* Statistics */
> -	nfsd_cache_init();	/* RPC reply cache */
> +	retval = nfsd_reply_cache_init();
> +	if (retval)
> +		goto out_free_stat;
>  	nfsd_export_init();	/* Exports table */
>  	nfsd_lockd_init();	/* lockd->nfsd callbacks */
>  	nfsd_idmap_init();      /* Name to ID mapping */
> @@ -700,11 +702,12 @@ static int __init init_nfsd(void)
>  out_free_all:
>  	nfsd_idmap_shutdown();
>  	nfsd_export_shutdown();
> -	nfsd_cache_shutdown();
> +	nfsd_reply_cache_shutdown();
>  	remove_proc_entry("fs/nfs/exports", NULL);
>  	remove_proc_entry("fs/nfs", NULL);
> -	nfsd_stat_shutdown();
>  	nfsd_lockd_shutdown();
> +out_free_stat:
> +	nfsd_stat_shutdown();
>  	nfsd4_free_slabs();
>  	return retval;
>  }
> @@ -712,7 +715,7 @@ out_free_all:
>  static void __exit exit_nfsd(void)
>  {
>  	nfsd_export_shutdown();
> -	nfsd_cache_shutdown();
> +	nfsd_reply_cache_shutdown();
>  	remove_proc_entry("fs/nfs/exports", NULL);
>  	remove_proc_entry("fs/nfs", NULL);
>  	nfsd_stat_shutdown();
> diff --git a/include/linux/nfsd/cache.h b/include/linux/nfsd/cache.h
> index 007480c..7b5d784 100644
> --- a/include/linux/nfsd/cache.h
> +++ b/include/linux/nfsd/cache.h
> @@ -72,8 +72,8 @@ enum {
>   */
>  #define RC_DELAY		(HZ/5)
>  
> -void	nfsd_cache_init(void);
> -void	nfsd_cache_shutdown(void);
> +int	nfsd_reply_cache_init(void);
> +void	nfsd_reply_cache_shutdown(void);
>  int	nfsd_cache_lookup(struct svc_rqst *, int);
>  void	nfsd_cache_update(struct svc_rqst *, int, __be32 *);
>  
>   


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