[PATCH v3 37/49] nfsd: dynamically allocate the nfsd-reply shrinker

[Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>]

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@xxxxxxxxxxxxx>
Acked-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
Acked-by: Jeff Layton <jlayton@xxxxxxxxxx>
---
 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