The following deadlock can occur between a process waiting for a client
to initialize in while walking the client list and another process
waiting for the nfs_clid_init_mutex so it can initialize that client:
Process 1 Process 2
--------- ---------
spin_lock(&nn->nfs_client_lock);
list_add_tail(&CLIENTA->cl_share_link,
&nn->nfs_client_list);
spin_unlock(&nn->nfs_client_lock);
spin_lock(&nn->nfs_client_lock);
list_add_tail(&CLIENTB->cl_share_link,
&nn->nfs_client_list);
spin_unlock(&nn->nfs_client_lock);
mutex_lock(&nfs_clid_init_mutex);
nfs41_walk_client_list(clp, result, cred);
nfs_wait_client_init_complete(CLIENTA);
(waiting for nfs_clid_init_mutex)
Add and initilize the client with the nfs_clid_init_mutex held in
order to prevent that deadlock.
Signed-off-by: Scott Mayhew <smayhew@xxxxxxxxxx>
---
fs/nfs/client.c | 21 +++++++++++++++++++--
fs/nfs/nfs4state.c | 4 ----
2 files changed, 19 insertions(+), 6 deletions(-)
diff --git a/fs/nfs/client.c b/fs/nfs/client.c
index 0ac2fb1..db38c47 100644
--- a/fs/nfs/client.c
+++ b/fs/nfs/client.c
@@ -60,6 +60,7 @@ static DECLARE_WAIT_QUEUE_HEAD(nfs_client_active_wq);
static DEFINE_SPINLOCK(nfs_version_lock);
static DEFINE_MUTEX(nfs_version_mutex);
static LIST_HEAD(nfs_versions);
+static DEFINE_MUTEX(nfs_clid_init_mutex);
/*
* RPC cruft for NFS
@@ -386,7 +387,7 @@ nfs_found_client(const struct nfs_client_initdata *cl_init,
*/
struct nfs_client *nfs_get_client(const struct nfs_client_initdata *cl_init)
{
- struct nfs_client *clp, *new = NULL;
+ struct nfs_client *clp, *new = NULL, *result = NULL;
struct nfs_net *nn = net_generic(cl_init->net, nfs_net_id);
const struct nfs_rpc_ops *rpc_ops = cl_init->nfs_mod->rpc_ops;
@@ -407,11 +408,27 @@ struct nfs_client *nfs_get_client(const struct nfs_client_initdata *cl_init)
return nfs_found_client(cl_init, clp);
}
if (new) {
+ /* add and initialize the client with the
+ * nfs_clid_init_mutex held to prevent a deadlock
+ * with the server trunking detection
+ */
+ spin_unlock(&nn->nfs_client_lock);
+ mutex_lock(&nfs_clid_init_mutex);
+ spin_lock(&nn->nfs_client_lock);
+ clp = nfs_match_client(cl_init);
+ if (clp) {
+ spin_unlock(&nn->nfs_client_lock);
+ mutex_unlock(&nfs_clid_init_mutex);
+ new->rpc_ops->free_client(new);
+ return nfs_found_client(cl_init, clp);
+ }
list_add_tail(&new->cl_share_link,
&nn->nfs_client_list);
spin_unlock(&nn->nfs_client_lock);
new->cl_flags = cl_init->init_flags;
- return rpc_ops->init_client(new, cl_init);
+ result = rpc_ops->init_client(new, cl_init);
+ mutex_unlock(&nfs_clid_init_mutex);
+ return result;
}
spin_unlock(&nn->nfs_client_lock);
diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
index 54fd56d..668164e 100644
--- a/fs/nfs/nfs4state.c
+++ b/fs/nfs/nfs4state.c
@@ -77,8 +77,6 @@ const nfs4_stateid invalid_stateid = {
.type = NFS4_INVALID_STATEID_TYPE,
};
-static DEFINE_MUTEX(nfs_clid_init_mutex);
-
int nfs4_init_clientid(struct nfs_client *clp, struct rpc_cred *cred)
{
struct nfs4_setclientid_res clid = {
@@ -2164,7 +2162,6 @@ int nfs4_discover_server_trunking(struct nfs_client *clp,
clnt = clp->cl_rpcclient;
i = 0;
- mutex_lock(&nfs_clid_init_mutex);
again:
status = -ENOENT;
cred = nfs4_get_clid_cred(clp);
@@ -2232,7 +2229,6 @@ int nfs4_discover_server_trunking(struct nfs_client *clp,
}
out_unlock:
- mutex_unlock(&nfs_clid_init_mutex);
dprintk("NFS: %s: status = %d\n", __func__, status);
return status;
}
--
2.9.5
--
To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
