[PATCH 3/7] nfsd: filecache: move globals nfsd_file_lru and nfsd_file_shrinker to be per-net

NeilBrown
2025-01-27T01:23:41Z

The final freeing of nfsd files is done by per-net nfsd threads (which
call nfsd_file_net_dispose()) so it makes some sense to make more of the
freeing infrastructure to be per-net - in struct nfsd_fcache_disposal.

This is a step towards replacing the list_lru with simple lists which
each share the per-net lock in nfsd_fcache_disposal and will require
less list walking.

As the net is always shutdown before there is any chance that the rest
of the filecache is shut down we can removed the tests on
NFSD_FILE_CACHE_UP.

For the filecache stats file, which assumes a global lru, we keep a
separate counter which includes all files in all netns lrus.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: NeilBrown <neilb@suse.de>
---
fs/nfsd/filecache.c | 128 +++++++++++++++++++++++++-------------------
1 file changed, 72 insertions(+), 56 deletions(-)

diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c
index 549969d4aa7c..55f69bcde500 100644
--- a/fs/nfsd/filecache.c
+++ b/fs/nfsd/filecache.c
@@ -60,18 +60,20 @@ static DEFINE_PER_CPU(unsigned long, nfsd_file_allocations);
static DEFINE_PER_CPU(unsigned long, nfsd_file_releases);
static DEFINE_PER_CPU(unsigned long, nfsd_file_total_age);
static DEFINE_PER_CPU(unsigned long, nfsd_file_evictions);
+static DEFINE_PER_CPU(unsigned long, nfsd_file_lru_total);

struct nfsd_fcache_disposal {
spinlock_t lock;
+ struct list_lru file_lru;
struct list_head freeme;
+ struct delayed_work filecache_laundrette;
+ struct shrinker *file_shrinker;
};

static struct kmem_cache *nfsd_file_slab;
static struct kmem_cache *nfsd_file_mark_slab;
-static struct list_lru nfsd_file_lru;
static unsigned long nfsd_file_flags;
static struct fsnotify_group *nfsd_file_fsnotify_group;
-static struct delayed_work nfsd_filecache_laundrette;
static struct rhltable nfsd_file_rhltable
____cacheline_aligned_in_smp;

@@ -109,11 +111,18 @@ static const struct rhashtable_params nfsd_file_rhash_params = {
};

static void
-nfsd_file_schedule_laundrette(void)
+nfsd_file_schedule_laundrette(struct nfsd_fcache_disposal *l)
{
- if (test_bit(NFSD_FILE_CACHE_UP, &nfsd_file_flags))
- queue_delayed_work(system_unbound_wq, &nfsd_filecache_laundrette,
- NFSD_LAUNDRETTE_DELAY);
+ queue_delayed_work(system_unbound_wq, &l->filecache_laundrette,
+ NFSD_LAUNDRETTE_DELAY);
+}
+
+static void
+nfsd_file_schedule_laundrette_net(struct net *net)
+{
+ struct nfsd_net *nn = net_generic(net, nfsd_net_id);
+
+ nfsd_file_schedule_laundrette(nn->fcache_disposal);
}

static void
@@ -318,11 +327,14 @@ nfsd_file_check_writeback(struct nfsd_file *nf)
mapping_tagged(mapping, PAGECACHE_TAG_WRITEBACK);
}

-
static bool nfsd_file_lru_add(struct nfsd_file *nf)
{
+ struct nfsd_net *nn = net_generic(nf->nf_net, nfsd_net_id);
+ struct nfsd_fcache_disposal *l = nn->fcache_disposal;
+
set_bit(NFSD_FILE_REFERENCED, &nf->nf_flags);
- if (list_lru_add_obj(&nfsd_file_lru, &nf->nf_lru)) {
+ if (list_lru_add_obj(&l->file_lru, &nf->nf_lru)) {
+ this_cpu_inc(nfsd_file_lru_total);
trace_nfsd_file_lru_add(nf);
return true;
}
@@ -331,7 +343,11 @@ static bool nfsd_file_lru_add(struct nfsd_file *nf)

static bool nfsd_file_lru_remove(struct nfsd_file *nf)
{
- if (list_lru_del_obj(&nfsd_file_lru, &nf->nf_lru)) {
+ struct nfsd_net *nn = net_generic(nf->nf_net, nfsd_net_id);
+ struct nfsd_fcache_disposal *l = nn->fcache_disposal;
+
+ if (list_lru_del_obj(&l->file_lru, &nf->nf_lru)) {
+ this_cpu_dec(nfsd_file_lru_total);
trace_nfsd_file_lru_del(nf);
return true;
}
@@ -371,7 +387,7 @@ nfsd_file_put(struct nfsd_file *nf)

/* Try to add it to the LRU. If that fails, decrement. */
if (nfsd_file_lru_add(nf)) {
- nfsd_file_schedule_laundrette();
+ nfsd_file_schedule_laundrette_net(nf->nf_net);
return;
}

@@ -525,12 +541,14 @@ nfsd_file_lru_cb(struct list_head *item, struct list_lru_one *lru,
if (!refcount_dec_and_test(&nf->nf_ref)) {
trace_nfsd_file_gc_in_use(nf);
list_lru_isolate(lru, &nf->nf_lru);
+ this_cpu_dec(nfsd_file_lru_total);
return LRU_REMOVED;
}

/* Refcount went to zero. Unhash it and queue it to the dispose list */
nfsd_file_unhash(nf);
list_lru_isolate(lru, &nf->nf_lru);
+ this_cpu_dec(nfsd_file_lru_total);
list_add(&nf->nf_gc, head);
this_cpu_inc(nfsd_file_evictions);
trace_nfsd_file_gc_disposed(nf);
@@ -538,18 +556,18 @@ nfsd_file_lru_cb(struct list_head *item, struct list_lru_one *lru,
}

static void
-nfsd_file_gc(void)
+nfsd_file_gc(struct nfsd_fcache_disposal *l)
{
- unsigned long remaining = list_lru_count(&nfsd_file_lru);
+ unsigned long remaining = list_lru_count(&l->file_lru);
LIST_HEAD(dispose);
unsigned long ret;

while (remaining > 0) {
unsigned long num_to_scan = min(remaining, NFSD_FILE_GC_BATCH);

- ret = list_lru_walk(&nfsd_file_lru, nfsd_file_lru_cb,
+ ret = list_lru_walk(&l->file_lru, nfsd_file_lru_cb,
&dispose, num_to_scan);
- trace_nfsd_file_gc_removed(ret, list_lru_count(&nfsd_file_lru));
+ trace_nfsd_file_gc_removed(ret, list_lru_count(&l->file_lru));
nfsd_file_dispose_list_delayed(&dispose);
remaining -= num_to_scan;
}
@@ -558,32 +576,36 @@ nfsd_file_gc(void)
static void
nfsd_file_gc_worker(struct work_struct *work)
{
- nfsd_file_gc();
- if (list_lru_count(&nfsd_file_lru))
- nfsd_file_schedule_laundrette();
+ struct nfsd_fcache_disposal *l = container_of(
+ work, struct nfsd_fcache_disposal, filecache_laundrette.work);
+ nfsd_file_gc(l);
+ if (list_lru_count(&l->file_lru))
+ nfsd_file_schedule_laundrette(l);
}

static unsigned long
nfsd_file_lru_count(struct shrinker *s, struct shrink_control *sc)
{
- return list_lru_count(&nfsd_file_lru);
+ struct nfsd_fcache_disposal *l = s->private_data;
+
+ return list_lru_count(&l->file_lru);
}

static unsigned long
nfsd_file_lru_scan(struct shrinker *s, struct shrink_control *sc)
{
+ struct nfsd_fcache_disposal *l = s->private_data;
+
LIST_HEAD(dispose);
unsigned long ret;

- ret = list_lru_shrink_walk(&nfsd_file_lru, sc,
+ ret = list_lru_shrink_walk(&l->file_lru, sc,
nfsd_file_lru_cb, &dispose);
- trace_nfsd_file_shrinker_removed(ret, list_lru_count(&nfsd_file_lru));
+ trace_nfsd_file_shrinker_removed(ret, list_lru_count(&l->file_lru));
nfsd_file_dispose_list_delayed(&dispose);
return ret;
}

-static struct shrinker *nfsd_file_shrinker;
-
/**
* nfsd_file_cond_queue - conditionally unhash and queue a nfsd_file
* @nf: nfsd_file to attempt to queue
@@ -763,29 +785,10 @@ nfsd_file_cache_init(void)
goto out_err;
}

- ret = list_lru_init(&nfsd_file_lru);
- if (ret) {
- pr_err("nfsd: failed to init nfsd_file_lru: %d\n", ret);
- goto out_err;
- }
-
- nfsd_file_shrinker = shrinker_alloc(0, "nfsd-filecache");
- if (!nfsd_file_shrinker) {
- ret = -ENOMEM;
- pr_err("nfsd: failed to allocate nfsd_file_shrinker\n");
- goto out_lru;
- }
-
- nfsd_file_shrinker->count_objects = nfsd_file_lru_count;
- nfsd_file_shrinker->scan_objects = nfsd_file_lru_scan;
- nfsd_file_shrinker->seeks = 1;
-
- shrinker_register(nfsd_file_shrinker);
-
ret = lease_register_notifier(&nfsd_file_lease_notifier);
if (ret) {
pr_err("nfsd: unable to register lease notifier: %d\n", ret);
- goto out_shrinker;
+ goto out_err;
}

nfsd_file_fsnotify_group = fsnotify_alloc_group(&nfsd_file_fsnotify_ops,
@@ -798,17 +801,12 @@ nfsd_file_cache_init(void)
goto out_notifier;
}

- INIT_DELAYED_WORK(&nfsd_filecache_laundrette, nfsd_file_gc_worker);
out:
if (ret)
clear_bit(NFSD_FILE_CACHE_UP, &nfsd_file_flags);
return ret;
out_notifier:
lease_unregister_notifier(&nfsd_file_lease_notifier);
-out_shrinker:
- shrinker_free(nfsd_file_shrinker);
-out_lru:
- list_lru_destroy(&nfsd_file_lru);
out_err:
kmem_cache_destroy(nfsd_file_slab);
nfsd_file_slab = NULL;
@@ -860,13 +858,38 @@ nfsd_alloc_fcache_disposal(void)
if (!l)
return NULL;
spin_lock_init(&l->lock);
+ INIT_DELAYED_WORK(&l->filecache_laundrette, nfsd_file_gc_worker);
INIT_LIST_HEAD(&l->freeme);
+ l->file_shrinker = shrinker_alloc(0, "nfsd-filecache");
+ if (!l->file_shrinker) {
+ pr_err("nfsd: failed to allocate nfsd_file_shrinker\n");
+ kfree(l);
+ return NULL;
+ }
+ l->file_shrinker->count_objects = nfsd_file_lru_count;
+ l->file_shrinker->scan_objects = nfsd_file_lru_scan;
+ l->file_shrinker->seeks = 1;
+ l->file_shrinker->private_data = l;
+
+ /* if file_lru is not zeroed it can trigger a bug: ->key is the problem */
+ memset(&l->file_lru, 0, sizeof(l->file_lru));
+ if (list_lru_init(&l->file_lru)) {
+ pr_err("nfsd: failed to init nfsd_file_lru\n");
+ shrinker_free(l->file_shrinker);
+ kfree(l);
+ return NULL;
+ }
+
+ shrinker_register(l->file_shrinker);
return l;
}

static void
nfsd_free_fcache_disposal(struct nfsd_fcache_disposal *l)
{
+ cancel_delayed_work_sync(&l->filecache_laundrette);
+ shrinker_free(l->file_shrinker);
+ list_lru_destroy(&l->file_lru);
nfsd_file_dispose_list(&l->freeme);
kfree(l);
}
@@ -919,14 +942,7 @@ nfsd_file_cache_shutdown(void)
return;

lease_unregister_notifier(&nfsd_file_lease_notifier);
- shrinker_free(nfsd_file_shrinker);
- /*
- * make sure all callers of nfsd_file_lru_cb are done before
- * calling nfsd_file_cache_purge
- */
- cancel_delayed_work_sync(&nfsd_filecache_laundrette);
__nfsd_file_cache_purge(NULL);
- list_lru_destroy(&nfsd_file_lru);
rcu_barrier();
fsnotify_put_group(nfsd_file_fsnotify_group);
nfsd_file_fsnotify_group = NULL;
@@ -944,6 +960,7 @@ nfsd_file_cache_shutdown(void)
per_cpu(nfsd_file_releases, i) = 0;
per_cpu(nfsd_file_total_age, i) = 0;
per_cpu(nfsd_file_evictions, i) = 0;
+ per_cpu(nfsd_file_lru_total, i) = 0;
}
}

@@ -1297,8 +1314,6 @@ int nfsd_file_cache_stats_show(struct seq_file *m, void *v)
struct bucket_table *tbl;
struct rhashtable *ht;

- lru = list_lru_count(&nfsd_file_lru);
-
rcu_read_lock();
ht = &nfsd_file_rhltable.ht;
count = atomic_read(&ht->nelems);
@@ -1309,6 +1324,7 @@ int nfsd_file_cache_stats_show(struct seq_file *m, void *v)
mutex_unlock(&nfsd_mutex);

for_each_possible_cpu(i) {
+ lru += per_cpu(nfsd_file_lru_total, i);
hits += per_cpu(nfsd_file_cache_hits, i);
acquisitions += per_cpu(nfsd_file_acquisitions, i);
allocations += per_cpu(nfsd_file_allocations, i);
--
2.47.1