From 1463b38e7cf34d4cc60f41daff459ad807b2e408 Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Wed, 1 Dec 2021 10:58:14 +1100 Subject: [PATCH] NFSD: simplify per-net file cache management We currently have a 'laundrette' for closing cached files - a different work-item for each network-namespace. These 'laundrettes' (aka struct nfsd_fcache_disposal) are currently on a list, and are freed using rcu. The list is not necessary as we have a per-namespace structure (struct nfsd_net) which can hold a link to the nfsd_fcache_disposal. The use of kfree_rcu is also unnecessary as the cache is cleaned of all files associated with a given namespace, and no new files can be added, before the nfsd_fcache_disposal is freed. So add a '->fcache_disposal' link to nfsd_net, and discard the list management and rcu usage. Signed-off-by: NeilBrown Signed-off-by: Chuck Lever --- fs/nfsd/filecache.c | 76 +++++++++++------------------------------------------ fs/nfsd/netns.h | 2 ++ 2 files changed, 17 insertions(+), 61 deletions(-) diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c index fdf89fc..aa5dca4 100644 --- a/fs/nfsd/filecache.c +++ b/fs/nfsd/filecache.c @@ -44,12 +44,9 @@ struct nfsd_fcache_bucket { static DEFINE_PER_CPU(unsigned long, nfsd_file_cache_hits); struct nfsd_fcache_disposal { - struct list_head list; struct work_struct work; - struct net *net; spinlock_t lock; struct list_head freeme; - struct rcu_head rcu; }; static struct workqueue_struct *nfsd_filecache_wq __read_mostly; @@ -62,8 +59,6 @@ static long nfsd_file_lru_flags; static struct fsnotify_group *nfsd_file_fsnotify_group; static atomic_long_t nfsd_filecache_count; static struct delayed_work nfsd_filecache_laundrette; -static DEFINE_SPINLOCK(laundrette_lock); -static LIST_HEAD(laundrettes); static void nfsd_file_gc(void); @@ -367,19 +362,13 @@ nfsd_file_list_remove_disposal(struct list_head *dst, static void nfsd_file_list_add_disposal(struct list_head *files, struct net *net) { - struct nfsd_fcache_disposal *l; + struct nfsd_net *nn = net_generic(net, nfsd_net_id); + struct nfsd_fcache_disposal *l = nn->fcache_disposal; - rcu_read_lock(); - list_for_each_entry_rcu(l, &laundrettes, list) { - if (l->net == net) { - spin_lock(&l->lock); - list_splice_tail_init(files, &l->freeme); - spin_unlock(&l->lock); - queue_work(nfsd_filecache_wq, &l->work); - break; - } - } - rcu_read_unlock(); + spin_lock(&l->lock); + list_splice_tail_init(files, &l->freeme); + spin_unlock(&l->lock); + queue_work(nfsd_filecache_wq, &l->work); } static void @@ -755,7 +744,7 @@ nfsd_file_cache_purge(struct net *net) } static struct nfsd_fcache_disposal * -nfsd_alloc_fcache_disposal(struct net *net) +nfsd_alloc_fcache_disposal(void) { struct nfsd_fcache_disposal *l; @@ -763,7 +752,6 @@ nfsd_alloc_fcache_disposal(struct net *net) if (!l) return NULL; INIT_WORK(&l->work, nfsd_file_delayed_close); - l->net = net; spin_lock_init(&l->lock); INIT_LIST_HEAD(&l->freeme); return l; @@ -772,61 +760,27 @@ nfsd_alloc_fcache_disposal(struct net *net) static void nfsd_free_fcache_disposal(struct nfsd_fcache_disposal *l) { - rcu_assign_pointer(l->net, NULL); cancel_work_sync(&l->work); nfsd_file_dispose_list(&l->freeme); - kfree_rcu(l, rcu); -} - -static void -nfsd_add_fcache_disposal(struct nfsd_fcache_disposal *l) -{ - spin_lock(&laundrette_lock); - list_add_tail_rcu(&l->list, &laundrettes); - spin_unlock(&laundrette_lock); -} - -static void -nfsd_del_fcache_disposal(struct nfsd_fcache_disposal *l) -{ - spin_lock(&laundrette_lock); - list_del_rcu(&l->list); - spin_unlock(&laundrette_lock); -} - -static int -nfsd_alloc_fcache_disposal_net(struct net *net) -{ - struct nfsd_fcache_disposal *l; - - l = nfsd_alloc_fcache_disposal(net); - if (!l) - return -ENOMEM; - nfsd_add_fcache_disposal(l); - return 0; + kfree(l); } static void nfsd_free_fcache_disposal_net(struct net *net) { - struct nfsd_fcache_disposal *l; + struct nfsd_net *nn = net_generic(net, nfsd_net_id); + struct nfsd_fcache_disposal *l = nn->fcache_disposal; - rcu_read_lock(); - list_for_each_entry_rcu(l, &laundrettes, list) { - if (l->net != net) - continue; - nfsd_del_fcache_disposal(l); - rcu_read_unlock(); - nfsd_free_fcache_disposal(l); - return; - } - rcu_read_unlock(); + nfsd_free_fcache_disposal(l); } int nfsd_file_cache_start_net(struct net *net) { - return nfsd_alloc_fcache_disposal_net(net); + struct nfsd_net *nn = net_generic(net, nfsd_net_id); + + nn->fcache_disposal = nfsd_alloc_fcache_disposal(); + return nn->fcache_disposal ? 0 : -ENOMEM; } void diff --git a/fs/nfsd/netns.h b/fs/nfsd/netns.h index 021acdc..9e8b77d 100644 --- a/fs/nfsd/netns.h +++ b/fs/nfsd/netns.h @@ -185,6 +185,8 @@ struct nfsd_net { /* utsname taken from the process that starts the server */ char nfsd_name[UNX_MAXNODENAME+1]; + + struct nfsd_fcache_disposal *fcache_disposal; }; /* Simple check to find out if a given net was properly initialized */ -- 2.7.4