Commit 3a505845 authored by Trond Myklebust's avatar Trond Myklebust
Browse files

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: default avatarTrond Myklebust <trond.myklebust@primarydata.com>
parent bae6746f

fs/nfs/dir.c

+35 −7
Original line number Diff line number Diff line
@@ -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 @@ nfs_access_cache_scan(struct shrinker *shrink, struct shrink_control *sc) 
	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);