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

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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: zhangxiaoxu (A) <zhangxiaoxu5@huawei.com>
Fixes: 5fcdfacc01 ("NFSv4: Return delegations synchronously in evict_inode")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
This commit is contained in:
Trond Myklebust 2021-06-01 11:10:05 -04:00
parent d1b5c230e9
commit dfe1fe75e0
2 changed files with 12 additions and 1 deletions
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1
fs/nfs/nfs4_fs.h
View File

@ -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;

12
fs/nfs/nfs4proc.c
View File

@ -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;