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

Qi Zheng
2023-08-07T11:21:17Z

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@bytedance.com>
Acked-by: Chuck Lever <chuck.lever@oracle.com>
Acked-by: Jeff Layton <jlayton@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