On Mon, 2023-07-24 at 17:43 +0800, Qi Zheng wrote:
> In preparation for implementing lockless slab shrink, use new APIs to
> dynamically allocate the nfsd-reply shrinker, so that it can be freed
> asynchronously using kfree_rcu(). Then it doesn't need to wait for RCU
> read-side critical section when releasing the struct nfsd_net.
>
> Acked-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
> Signed-off-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
> ---
> fs/nfsd/netns.h | 2 +-
> fs/nfsd/nfscache.c | 31 ++++++++++++++++---------------
> 2 files changed, 17 insertions(+), 16 deletions(-)
>
> diff --git a/fs/nfsd/netns.h b/fs/nfsd/netns.h
> index f669444d5336..ab303a8b77d5 100644
> --- a/fs/nfsd/netns.h
> +++ b/fs/nfsd/netns.h
> @@ -177,7 +177,7 @@ struct nfsd_net {
> /* size of cache when we saw the longest hash chain */
> unsigned int longest_chain_cachesize;
>
> - struct shrinker nfsd_reply_cache_shrinker;
> + struct shrinker *nfsd_reply_cache_shrinker;
>
> /* tracking server-to-server copy mounts */
> spinlock_t nfsd_ssc_lock;
> diff --git a/fs/nfsd/nfscache.c b/fs/nfsd/nfscache.c
> index 6eb3d7bdfaf3..9f0ab65e4125 100644
> --- a/fs/nfsd/nfscache.c
> +++ b/fs/nfsd/nfscache.c
> @@ -200,26 +200,29 @@ int nfsd_reply_cache_init(struct nfsd_net *nn)
> {
> unsigned int hashsize;
> unsigned int i;
> - int status = 0;
>
> nn->max_drc_entries = nfsd_cache_size_limit();
> atomic_set(&nn->num_drc_entries, 0);
> hashsize = nfsd_hashsize(nn->max_drc_entries);
> nn->maskbits = ilog2(hashsize);
>
> - nn->nfsd_reply_cache_shrinker.scan_objects = nfsd_reply_cache_scan;
> - nn->nfsd_reply_cache_shrinker.count_objects = nfsd_reply_cache_count;
> - nn->nfsd_reply_cache_shrinker.seeks = 1;
> - status = register_shrinker(&nn->nfsd_reply_cache_shrinker,
> - "nfsd-reply:%s", nn->nfsd_name);
> - if (status)
> - return status;
> -
> nn->drc_hashtbl = kvzalloc(array_size(hashsize,
> sizeof(*nn->drc_hashtbl)), GFP_KERNEL);
> if (!nn->drc_hashtbl)
> + return -ENOMEM;
> +
> + nn->nfsd_reply_cache_shrinker = shrinker_alloc(0, "nfsd-reply:%s",
> + nn->nfsd_name);
> + if (!nn->nfsd_reply_cache_shrinker)
> goto out_shrinker;
>
> + nn->nfsd_reply_cache_shrinker->scan_objects = nfsd_reply_cache_scan;
> + nn->nfsd_reply_cache_shrinker->count_objects = nfsd_reply_cache_count;
> + nn->nfsd_reply_cache_shrinker->seeks = 1;
> + nn->nfsd_reply_cache_shrinker->private_data = nn;
> +
> + shrinker_register(nn->nfsd_reply_cache_shrinker);
> +
> for (i = 0; i < hashsize; i++) {
> INIT_LIST_HEAD(&nn->drc_hashtbl[i].lru_head);
> spin_lock_init(&nn->drc_hashtbl[i].cache_lock);
> @@ -228,7 +231,7 @@ int nfsd_reply_cache_init(struct nfsd_net *nn)
>
> return 0;
> out_shrinker:
> - unregister_shrinker(&nn->nfsd_reply_cache_shrinker);
> + kvfree(nn->drc_hashtbl);
> printk(KERN_ERR "nfsd: failed to allocate reply cache\n");
> return -ENOMEM;
> }
> @@ -238,7 +241,7 @@ void nfsd_reply_cache_shutdown(struct nfsd_net *nn)
> struct nfsd_cacherep *rp;
> unsigned int i;
>
> - unregister_shrinker(&nn->nfsd_reply_cache_shrinker);
> + shrinker_unregister(nn->nfsd_reply_cache_shrinker);
>
> for (i = 0; i < nn->drc_hashsize; i++) {
> struct list_head *head = &nn->drc_hashtbl[i].lru_head;
> @@ -322,8 +325,7 @@ nfsd_prune_bucket_locked(struct nfsd_net *nn, struct nfsd_drc_bucket *b,
> static unsigned long
> nfsd_reply_cache_count(struct shrinker *shrink, struct shrink_control *sc)
> {
> - struct nfsd_net *nn = container_of(shrink,
> - struct nfsd_net, nfsd_reply_cache_shrinker);
> + struct nfsd_net *nn = shrink->private_data;
>
> return atomic_read(&nn->num_drc_entries);
> }
> @@ -342,8 +344,7 @@ nfsd_reply_cache_count(struct shrinker *shrink, struct shrink_control *sc)
> static unsigned long
> nfsd_reply_cache_scan(struct shrinker *shrink, struct shrink_control *sc)
> {
> - struct nfsd_net *nn = container_of(shrink,
> - struct nfsd_net, nfsd_reply_cache_shrinker);
> + struct nfsd_net *nn = shrink->private_data;
> unsigned long freed = 0;
> LIST_HEAD(dispose);
> unsigned int i;
Acked-by: Jeff Layton <jlayton@xxxxxxxxxx>
