From 3a505845cd58a7ff3bc75f96572045d8de34e34e Mon Sep 17 00:00:00 2001 From: Trond Myklebust Date: Mon, 21 Jul 2014 13:53:48 -0400 Subject: [PATCH] NFS: Enforce an upper limit on the number of cached access call This may be used to limit the number of cached credentials building up inside the access cache. Signed-off-by: Trond Myklebust --- fs/nfs/dir.c | 42 +++++++++++++++++++++++++++++++++++------- 1 file changed, 35 insertions(+), 7 deletions(-) diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c index 4a3d4ef76127..7dc88bb4296c 100644 --- a/fs/nfs/dir.c +++ b/fs/nfs/dir.c @@ -2028,6 +2028,10 @@ static DEFINE_SPINLOCK(nfs_access_lru_lock); static LIST_HEAD(nfs_access_lru_list); static atomic_long_t nfs_access_nr_entries; +static unsigned long nfs_access_max_cachesize = ULONG_MAX; +module_param(nfs_access_max_cachesize, ulong, 0644); +MODULE_PARM_DESC(nfs_access_max_cachesize, "NFS access maximum total cache length"); + static void nfs_access_free_entry(struct nfs_access_entry *entry) { put_rpccred(entry->cred); @@ -2048,19 +2052,14 @@ static void nfs_access_free_list(struct list_head *head) } } -unsigned long -nfs_access_cache_scan(struct shrinker *shrink, struct shrink_control *sc) +static unsigned long +nfs_do_access_cache_scan(unsigned int nr_to_scan) { LIST_HEAD(head); struct nfs_inode *nfsi, *next; struct nfs_access_entry *cache; - int nr_to_scan = sc->nr_to_scan; - gfp_t gfp_mask = sc->gfp_mask; long freed = 0; - if ((gfp_mask & GFP_KERNEL) != GFP_KERNEL) - return SHRINK_STOP; - spin_lock(&nfs_access_lru_lock); list_for_each_entry_safe(nfsi, next, &nfs_access_lru_list, access_cache_inode_lru) { struct inode *inode; @@ -2093,12 +2092,40 @@ remove_lru_entry: return freed; } +unsigned long +nfs_access_cache_scan(struct shrinker *shrink, struct shrink_control *sc) +{ + int nr_to_scan = sc->nr_to_scan; + gfp_t gfp_mask = sc->gfp_mask; + + if ((gfp_mask & GFP_KERNEL) != GFP_KERNEL) + return SHRINK_STOP; + return nfs_do_access_cache_scan(nr_to_scan); +} + + unsigned long nfs_access_cache_count(struct shrinker *shrink, struct shrink_control *sc) { return vfs_pressure_ratio(atomic_long_read(&nfs_access_nr_entries)); } +static void +nfs_access_cache_enforce_limit(void) +{ + long nr_entries = atomic_long_read(&nfs_access_nr_entries); + unsigned long diff; + unsigned int nr_to_scan; + + if (nr_entries < 0 || nr_entries <= nfs_access_max_cachesize) + return; + nr_to_scan = 100; + diff = nr_entries - nfs_access_max_cachesize; + if (diff < nr_to_scan) + nr_to_scan = diff; + nfs_do_access_cache_scan(nr_to_scan); +} + static void __nfs_access_zap_cache(struct nfs_inode *nfsi, struct list_head *head) { struct rb_root *root_node = &nfsi->access_cache; @@ -2244,6 +2271,7 @@ void nfs_access_add_cache(struct inode *inode, struct nfs_access_entry *set) &nfs_access_lru_list); spin_unlock(&nfs_access_lru_lock); } + nfs_access_cache_enforce_limit(); } EXPORT_SYMBOL_GPL(nfs_access_add_cache); -- 2.20.1