linux-ext4 - [PATCH 16/29] NFSD: dynamically allocate the nfsd-reply shrinker

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Date:   Thu, 22 Jun 2023 16:53:22 +0800
From:   Qi Zheng <zhengqi.arch@...edance.com>
To:     akpm@...ux-foundation.org, david@...morbit.com, tkhai@...ru,
        vbabka@...e.cz, roman.gushchin@...ux.dev, djwong@...nel.org,
        brauner@...nel.org, paulmck@...nel.org, tytso@....edu
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-arm-msm@...r.kernel.org, dm-devel@...hat.com,
        linux-raid@...r.kernel.org, linux-bcache@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
        linux-nfs@...r.kernel.org, linux-xfs@...r.kernel.org,
        linux-btrfs@...r.kernel.org, Qi Zheng <zhengqi.arch@...edance.com>
Subject: [PATCH 16/29] NFSD: dynamically allocate the nfsd-reply shrinker

In preparation for implementing lockless slab shrink,
we need 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@...edance.com>
---
 fs/nfsd/netns.h    |  2 +-
 fs/nfsd/nfscache.c | 33 +++++++++++++++++++--------------
 2 files changed, 20 insertions(+), 15 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 041faa13b852..ec33de8e418b 100644
--- a/fs/nfsd/nfscache.c
+++ b/fs/nfsd/nfscache.c
@@ -173,19 +173,23 @@ int nfsd_reply_cache_init(struct nfsd_net *nn)
 	if (status)
 		goto out_nomem;
 
-	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)
-		goto out_stats_destroy;
-
 	nn->drc_hashtbl = kvzalloc(array_size(hashsize,
 				sizeof(*nn->drc_hashtbl)), GFP_KERNEL);
 	if (!nn->drc_hashtbl)
+		goto out_stats_destroy;
+
+	nn->nfsd_reply_cache_shrinker =
+		shrinker_alloc_and_init(nfsd_reply_cache_count,
+					nfsd_reply_cache_scan,
+					0, 1, 0, nn);
+	if (!nn->nfsd_reply_cache_shrinker)
 		goto out_shrinker;
 
+	status = register_shrinker(nn->nfsd_reply_cache_shrinker,
+				   "nfsd-reply:%s", nn->nfsd_name);
+	if (status)
+		goto out_register;
+
 	for (i = 0; i < hashsize; i++) {
 		INIT_LIST_HEAD(&nn->drc_hashtbl[i].lru_head);
 		spin_lock_init(&nn->drc_hashtbl[i].cache_lock);
@@ -193,8 +197,11 @@ int nfsd_reply_cache_init(struct nfsd_net *nn)
 	nn->drc_hashsize = hashsize;
 
 	return 0;
+
+out_register:
+	shrinker_free(nn->nfsd_reply_cache_shrinker);
 out_shrinker:
-	unregister_shrinker(&nn->nfsd_reply_cache_shrinker);
+	kvfree(nn->drc_hashtbl);
 out_stats_destroy:
 	nfsd_reply_cache_stats_destroy(nn);
 out_nomem:
@@ -207,7 +214,7 @@ void nfsd_reply_cache_shutdown(struct nfsd_net *nn)
 	struct svc_cacherep	*rp;
 	unsigned int i;
 
-	unregister_shrinker(&nn->nfsd_reply_cache_shrinker);
+	unregister_and_free_shrinker(nn->nfsd_reply_cache_shrinker);
 
 	for (i = 0; i < nn->drc_hashsize; i++) {
 		struct list_head *head = &nn->drc_hashtbl[i].lru_head;
@@ -297,8 +304,7 @@ prune_cache_entries(struct nfsd_net *nn)
 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);
 }
@@ -306,8 +312,7 @@ 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;
 
 	return prune_cache_entries(nn);
 }
-- 
2.30.2