path: root/fs/nfs/unlink.c
diff options
authorTrond Myklebust <Trond.Myklebust@netapp.com>2011-02-21 11:05:41 -0800
committerTrond Myklebust <Trond.Myklebust@netapp.com>2011-03-10 15:04:52 -0500
commitbf294b41cefcb22fc3139e0f42c5b3f06728bd5e (patch)
tree250251c040a2d2e278b5a2ddd03c8d20a27be129 /fs/nfs/unlink.c
parent214d93b02c4fe93638ad268613c9702a81ed9192 (diff)
SUNRPC: Close a race in __rpc_wait_for_completion_task()
Although they run as rpciod background tasks, under normal operation (i.e. no SIGKILL), functions like nfs_sillyrename(), nfs4_proc_unlck() and nfs4_do_close() want to be fully synchronous. This means that when we exit, we want all references to the rpc_task to be gone, and we want any dentry references etc. held by that task to be released. For this reason these functions call __rpc_wait_for_completion_task(), followed by rpc_put_task() in the expectation that the latter will be releasing the last reference to the rpc_task, and thus ensuring that the callback_ops->rpc_release() has been called synchronously. This patch fixes a race which exists due to the fact that rpciod calls rpc_complete_task() (in order to wake up the callers of __rpc_wait_for_completion_task()) and then subsequently calls rpc_put_task() without ensuring that these two steps are done atomically. In order to avoid adding new spin locks, the patch uses the existing waitqueue spin lock to order the rpc_task reference count releases between the waiting process and rpciod. The common case where nobody is waiting for completion is optimised for by checking if the RPC_TASK_ASYNC flag is cleared and/or if the rpc_task reference count is 1: in those cases we drop trying to grab the spin lock, and immediately free up the rpc_task. Those few processes that need to put the rpc_task from inside an asynchronous context and that do not care about ordering are given a new helper: rpc_put_task_async(). Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Diffstat (limited to 'fs/nfs/unlink.c')
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/nfs/unlink.c b/fs/nfs/unlink.c
index e313a51acdd1..6481d537d69d 100644
--- a/fs/nfs/unlink.c
+++ b/fs/nfs/unlink.c
@@ -180,7 +180,7 @@ static int nfs_do_call_unlink(struct dentry *parent, struct inode *dir, struct n
task_setup_data.rpc_client = NFS_CLIENT(dir);
task = rpc_run_task(&task_setup_data);
if (!IS_ERR(task))
- rpc_put_task(task);
+ rpc_put_task_async(task);
return 1;