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 b65aee4..09b3b71 100644
--- 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);