NFSv4: Fix the acl cache size calculation

Currently, we do not take into account the size of the 16 byte
struct nfs4_cached_acl header, when deciding whether or not we should
cache the acl data.  Consequently, we will end up allocating an
8k buffer in order to fit a maximum size 4k acl.

This patch adjusts the calculation so that we limit the cache size
to 4k for the acl header+data.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/nfs4proc.c

@@ -3737,9 +3737,10 @@ static inline ssize_t nfs4_read_cached_acl(struct inode *inode, char *buf, size_
 static void nfs4_write_cached_acl(struct inode *inode, struct page **pages, size_t pgbase, size_t acl_len)
 {
 	struct nfs4_cached_acl *acl;
+	size_t buflen = sizeof(*acl) + acl_len;
 
-	if (pages && acl_len <= PAGE_SIZE) {
-		acl = kmalloc(sizeof(*acl) + acl_len, GFP_KERNEL);
+	if (pages && buflen <= PAGE_SIZE) {
+		acl = kmalloc(buflen, GFP_KERNEL);
 		if (acl == NULL)
 			goto out;
 		acl->cached = 1;