NFS: Convert lookups of the lock context to RCU

Speed up lookups of an existing lock context by avoiding the inode->i_lock,
and using RCU instead.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index b65aee481d131d00734c057cd16f4532f2898211..09b3b7146ff4a4e5d345b1bdbaf8ca95b8f34a3b 100644 (file)
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -857,15 +857,14 @@ static void nfs_init_lock_context(struct nfs_lock_context *l_ctx)
 
 static struct nfs_lock_context *__nfs_find_lock_context(struct nfs_open_context *ctx)
 {
-       struct nfs_lock_context *head = &ctx->lock_context;
-       struct nfs_lock_context *pos = head;
+       struct nfs_lock_context *pos;
 
-       do {
+       list_for_each_entry_rcu(pos, &ctx->lock_context.list, list) {
                if (pos->lockowner != current->files)
                        continue;
-               refcount_inc(&pos->count);
-               return pos;
-       } while ((pos = list_entry(pos->list.next, typeof(*pos), list)) != head);
+               if (refcount_inc_not_zero(&pos->count))
+                       return pos;
+       }
        return NULL;
 }
 
@@ -874,10 +873,10 @@ struct nfs_lock_context *nfs_get_lock_context(struct nfs_open_context *ctx)
        struct nfs_lock_context *res, *new = NULL;
        struct inode *inode = d_inode(ctx->dentry);
 
-       spin_lock(&inode->i_lock);
+       rcu_read_lock();
        res = __nfs_find_lock_context(ctx);
+       rcu_read_unlock();
        if (res == NULL) {
-               spin_unlock(&inode->i_lock);
                new = kmalloc(sizeof(*new), GFP_KERNEL);
                if (new == NULL)
                        return ERR_PTR(-ENOMEM);
@@ -885,14 +884,14 @@ struct nfs_lock_context *nfs_get_lock_context(struct nfs_open_context *ctx)
                spin_lock(&inode->i_lock);
                res = __nfs_find_lock_context(ctx);
                if (res == NULL) {
-                       list_add_tail(&new->list, &ctx->lock_context.list);
+                       list_add_tail_rcu(&new->list, &ctx->lock_context.list);
                        new->open_context = ctx;
                        res = new;
                        new = NULL;
                }
+               spin_unlock(&inode->i_lock);
+               kfree(new);
        }
-       spin_unlock(&inode->i_lock);
-       kfree(new);
        return res;
 }
 EXPORT_SYMBOL_GPL(nfs_get_lock_context);
@@ -904,9 +903,9 @@ void nfs_put_lock_context(struct nfs_lock_context *l_ctx)
 
        if (!refcount_dec_and_lock(&l_ctx->count, &inode->i_lock))
                return;
-       list_del(&l_ctx->list);
+       list_del_rcu(&l_ctx->list);
        spin_unlock(&inode->i_lock);
-       kfree(l_ctx);
+       kfree_rcu(l_ctx, rcu_head);
 }
 EXPORT_SYMBOL_GPL(nfs_put_lock_context);
 

diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index a0831e9d19c9df9f26c6d0777e198c32241550b4..d2f4f88a0e66dcee7110a55be1092f2cdc0db029 100644 (file)
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -62,6 +62,7 @@ struct nfs_lock_context {
        struct nfs_open_context *open_context;
        fl_owner_t lockowner;
        atomic_t io_count;
+       struct rcu_head rcu_head;
 };
 
 struct nfs4_state;