nfsd: register a shrinker for DRC cache entries

Since we dynamically allocate them now, allow the system to call us up
to release them if it gets low on memory. Since these entries aren't
replaceable, only free ones that are expired or that are over the cap.
The the seeks value is set to '1' however to indicate that freeing the
these entries is low-cost.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

1 files changed, 23 insertions, 0 deletions

diff --git a/fs/nfsd/nfscache.c b/fs/nfsd/nfscache.c
index d7b088bee684..d16a5d6435f2 100644
--- a/fs/nfsd/nfscache.c
+++ b/fs/nfsd/nfscache.c
@@ -37,6 +37,13 @@ static inline u32 request_hash(u32 xid)
 
 static int      nfsd_cache_append(struct svc_rqst *rqstp, struct kvec *vec);
 static void     cache_cleaner_func(struct work_struct *unused);
+static int      nfsd_reply_cache_shrink(struct shrinker *shrink,
+                                        struct shrink_control *sc);
+
+struct shrinker nfsd_reply_cache_shrinker = {
+        .shrink = nfsd_reply_cache_shrink,
+        .seeks  = 1,
+};
 
 /*
  * locking for the reply cache:
@@ -110,6 +117,7 @@ nfsd_reply_cache_free(struct svc_cacherep *rp)
 
 int nfsd_reply_cache_init(void)
 {
+        register_shrinker(&nfsd_reply_cache_shrinker);
         drc_slab = kmem_cache_create("nfsd_drc", sizeof(struct svc_cacherep),
                                         0, 0, NULL);
         if (!drc_slab)
@@ -133,6 +141,7 @@ void nfsd_reply_cache_shutdown(void)
 {
         struct svc_cacherep     *rp;
 
+        unregister_shrinker(&nfsd_reply_cache_shrinker);
         cancel_delayed_work_sync(&cache_cleaner);
 
         while (!list_empty(&lru_head)) {
@@ -214,6 +223,20 @@ cache_cleaner_func(struct work_struct *unused)
         spin_unlock(&cache_lock);
 }
 
+static int
+nfsd_reply_cache_shrink(struct shrinker *shrink, struct shrink_control *sc)
+{
+        unsigned int num;
+
+        spin_lock(&cache_lock);
+        if (sc->nr_to_scan)
+                prune_cache_entries();
+        num = num_drc_entries;
+        spin_unlock(&cache_lock);
+
+        return num;
+}
+
 /*
  * Search the request hash for an entry that matches the given rqstp.
  * Must be called with cache_lock held. Returns the found entry or