Commit dfe1fe75 authored by Trond Myklebust's avatar Trond Myklebust
Browse files

NFSv4: Fix deadlock between nfs4_evict_inode() and nfs4_opendata_get_inode() 



If the inode is being evicted, but has to return a delegation first,
then it can cause a deadlock in the corner case where the server reboots
before the delegreturn completes, but while the call to iget5_locked() in
nfs4_opendata_get_inode() is waiting for the inode free to complete.
Since the open call still holds a session slot, the reboot recovery
cannot proceed.

In order to break the logjam, we can turn the delegation return into a
privileged operation for the case where we're evicting the inode. We
know that in that case, there can be no other state recovery operation
that conflicts.

Reported-by: default avatarzhangxiaoxu (A) <zhangxiaoxu5@huawei.com>
Fixes: 5fcdfacc ("NFSv4: Return delegations synchronously in evict_inode")
Signed-off-by: default avatarTrond Myklebust <trond.myklebust@hammerspace.com>
parent d1b5c230

fs/nfs/nfs4_fs.h

+1 −0
Original line number Diff line number Diff line
@@ -205,6 +205,7 @@ struct nfs4_exception { 
	struct inode *inode;

	nfs4_stateid *stateid;

	long timeout;

	unsigned char task_is_privileged : 1;

	unsigned char delay : 1,

		      recovering : 1,

		      retry : 1;

fs/nfs/nfs4proc.c

+11 −1
Original line number Diff line number Diff line
@@ -589,6 +589,8 @@ int nfs4_handle_exception(struct nfs_server *server, int errorcode, struct nfs4_ 
		goto out_retry;

	}

	if (exception->recovering) {

		if (exception->task_is_privileged)

			return -EDEADLOCK;

		ret = nfs4_wait_clnt_recover(clp);

		if (test_bit(NFS_MIG_FAILED, &server->mig_status))

			return -EIO;
@@ -614,6 +616,8 @@ nfs4_async_handle_exception(struct rpc_task *task, struct nfs_server *server, 
		goto out_retry;

	}

	if (exception->recovering) {

		if (exception->task_is_privileged)

			return -EDEADLOCK;

		rpc_sleep_on(&clp->cl_rpcwaitq, task, NULL);

		if (test_bit(NFS4CLNT_MANAGER_RUNNING, &clp->cl_state) == 0)

			rpc_wake_up_queued_task(&clp->cl_rpcwaitq, task);
@@ -6417,6 +6421,7 @@ static void nfs4_delegreturn_done(struct rpc_task *task, void *calldata) 
	struct nfs4_exception exception = {

		.inode = data->inode,

		.stateid = &data->stateid,

		.task_is_privileged = data->args.seq_args.sa_privileged,

	};



	if (!nfs4_sequence_done(task, &data->res.seq_res))
@@ -6540,7 +6545,6 @@ static int _nfs4_proc_delegreturn(struct inode *inode, const struct cred *cred, 
	data = kzalloc(sizeof(*data), GFP_NOFS);

	if (data == NULL)

		return -ENOMEM;

	nfs4_init_sequence(&data->args.seq_args, &data->res.seq_res, 1, 0);



	nfs4_state_protect(server->nfs_client,

			NFS_SP4_MACH_CRED_CLEANUP,
@@ -6571,6 +6575,12 @@ static int _nfs4_proc_delegreturn(struct inode *inode, const struct cred *cred, 
		}

	}



	if (!data->inode)

		nfs4_init_sequence(&data->args.seq_args, &data->res.seq_res, 1,

				   1);

	else

		nfs4_init_sequence(&data->args.seq_args, &data->res.seq_res, 1,

				   0);

	task_setup_data.callback_data = data;

	msg.rpc_argp = &data->args;

	msg.rpc_resp = &data->res;