NFS: Convert the NFS module list into an array

Using a linked list here seems unnecessarily complex, especially since
possible index values are '2', '3', and '4'. Let's just use an array for
direct access.

Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

diff --git a/fs/nfs/client.c b/fs/nfs/client.c
index 8bcc61a..5b547d0 100644 (file)
--- a/fs/nfs/client.c
+++ b/fs/nfs/client.c
@@ -56,7 +56,12 @@
 
 static DECLARE_WAIT_QUEUE_HEAD(nfs_client_active_wq);
 static DEFINE_RWLOCK(nfs_version_lock);
-static LIST_HEAD(nfs_versions);
+
+static struct nfs_subversion *nfs_version_mods[5] = {
+       [2] = NULL,
+       [3] = NULL,
+       [4] = NULL,
+};
 
 /*
  * RPC cruft for NFS
@@ -78,17 +83,14 @@ const struct rpc_program nfs_program = {
 static struct nfs_subversion *find_nfs_version(unsigned int version)
 {
        struct nfs_subversion *nfs;
-       read_lock(&nfs_version_lock);
-
-       list_for_each_entry(nfs, &nfs_versions, list) {
-               if (nfs->rpc_ops->version == version) {
-                       read_unlock(&nfs_version_lock);
-                       return nfs;
-               }
-       }
 
+       read_lock(&nfs_version_lock);
+       nfs = nfs_version_mods[version];
        read_unlock(&nfs_version_lock);
-       return ERR_PTR(-EPROTONOSUPPORT);
+
+       if (nfs == NULL)
+               return ERR_PTR(-EPROTONOSUPPORT);
+       return nfs;
 }
 
 struct nfs_subversion *get_nfs_version(unsigned int version)
@@ -114,7 +116,7 @@ void register_nfs_version(struct nfs_subversion *nfs)
 {
        write_lock(&nfs_version_lock);
 
-       list_add(&nfs->list, &nfs_versions);
+       nfs_version_mods[nfs->rpc_ops->version] = nfs;
        nfs_version[nfs->rpc_ops->version] = nfs->rpc_vers;
 
        write_unlock(&nfs_version_lock);
@@ -126,7 +128,7 @@ void unregister_nfs_version(struct nfs_subversion *nfs)
        write_lock(&nfs_version_lock);
 
        nfs_version[nfs->rpc_ops->version] = NULL;
-       list_del(&nfs->list);
+       nfs_version_mods[nfs->rpc_ops->version] = NULL;
 
        write_unlock(&nfs_version_lock);
 }

diff --git a/fs/nfs/nfs.h b/fs/nfs/nfs.h
index 0d3ce04..0329fc3 100644 (file)
--- a/fs/nfs/nfs.h
+++ b/fs/nfs/nfs.h
@@ -19,7 +19,6 @@ struct nfs_subversion {
        const struct nfs_rpc_ops *rpc_ops;      /* NFS operations */
        const struct super_operations *sops;    /* NFS Super operations */
        const struct xattr_handler * const *xattr;      /* NFS xattr handlers */
-       struct list_head list;          /* List of NFS versions */
 };
 
 struct nfs_subversion *get_nfs_version(unsigned int);