[PATCH v4 36/48] nfsd: dynamically allocate the nfsd-reply shrinker

[Qi Zheng]

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.

Signed-off-by: Qi Zheng <zhengqi.arch at bytedance.com>
Acked-by: Chuck Lever <chuck.lever at oracle.com>
Acked-by: Jeff Layton <jlayton at kernel.org>
---
 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 80621a709510..fd56a52aa5fb 100644
--- a/fs/nfsd/nfscache.c
+++ b/fs/nfsd/nfscache.c
@@ -201,26 +201,29 @@ 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);
@@ -229,7 +232,7 @@ 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;
 }
@@ -239,7 +242,7 @@ void nfsd_reply_cache_shutdown(struct nfsd_net *nn)
 	struct nfsd_cacherep *rp;
 	unsigned int i;
 
-	unregister_shrinker(&nn->nfsd_reply_cache_shrinker);
+	shrinker_free(nn->nfsd_reply_cache_shrinker);
 
 	for (i = 0; i < nn->drc_hashsize; i++) {
 		struct list_head *head = &nn->drc_hashtbl[i].lru_head;
@@ -323,8 +326,7 @@ 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);
 }
@@ -343,8 +345,7 @@ 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;
-- 
2.30.2