From: Scott Mayhew <smayhew@redhat.com>
Date: Tue, 5 Dec 2017 13:55:44 -0500
Subject: [PATCH] nfs: fix a deadlock in nfs client initialization
Git-commit: c156618e15101a9cc8c815108fec0300a0ec6637
Patch-mainline: v4.15-rc4
References: bsc#1074198
The following deadlock can occur between a process waiting for a client
to initialize in while walking the client list during nfsv4 server trunking
detection and another process waiting for the nfs_clid_init_mutex so it
can initialize that client:
Process 1 Process 2
Acked-by: NeilBrown <neilb@suse.com>
Signed-off-by: Neil Brown <neilb@suse.com>
--------- ---------
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)
Make sure nfs_match_client() only evaluates clients that have completed
initialization in order to prevent that deadlock.
This patch also fixes v4.0 trunking behavior by not marking the client
NFS_CS_READY until the clientid has been confirmed.
Signed-off-by: Scott Mayhew <smayhew@redhat.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
---
fs/nfs/client.c | 11 +++++++++++
fs/nfs/nfs4client.c | 17 +++++++++++++----
2 files changed, 24 insertions(+), 4 deletions(-)
--- a/fs/nfs/client.c
+++ b/fs/nfs/client.c
@@ -292,12 +292,23 @@ static struct nfs_client *nfs_match_clie
const struct sockaddr *sap = data->addr;
struct nfs_net *nn = net_generic(data->net, nfs_net_id);
+again:
list_for_each_entry(clp, &nn->nfs_client_list, cl_share_link) {
const struct sockaddr *clap = (struct sockaddr *)&clp->cl_addr;
/* Don't match clients that failed to initialise properly */
if (clp->cl_cons_state < 0)
continue;
+ /* If a client is still initializing then we need to wait */
+ if (clp->cl_cons_state > NFS_CS_READY) {
+ atomic_inc(&clp->cl_count);
+ spin_unlock(&nn->nfs_client_lock);
+ nfs_wait_client_init_complete(clp);
+ nfs_put_client(clp);
+ spin_lock(&nn->nfs_client_lock);
+ goto again;
+ }
+
/* Different NFS versions cannot share the same nfs_client */
if (clp->rpc_ops != data->nfs_mod->rpc_ops)
continue;
--- a/fs/nfs/nfs4client.c
+++ b/fs/nfs/nfs4client.c
@@ -404,15 +404,19 @@ struct nfs_client *nfs4_init_client(stru
if (error < 0)
goto error;
- if (!nfs4_has_session(clp))
- nfs_mark_client_ready(clp, NFS_CS_READY);
-
error = nfs4_discover_server_trunking(clp, &old);
if (error < 0)
goto error;
- if (clp != old)
+ if (clp != old) {
clp->cl_preserve_clid = true;
+ /*
+ * Mark the client as having failed initialization so other
+ * processes walking the nfs_client_list in nfs_match_client()
+ * won't try to use it.
+ */
+ nfs_mark_client_ready(clp, -EPERM);
+ }
nfs_put_client(clp);
return old;
@@ -538,6 +542,9 @@ int nfs40_walk_client_list(struct nfs_cl
spin_lock(&nn->nfs_client_lock);
list_for_each_entry(pos, &nn->nfs_client_list, cl_share_link) {
+ if (pos == new)
+ goto found;
+
status = nfs4_match_client(pos, new, &prev, nn);
if (status < 0)
goto out_unlock;
@@ -558,6 +565,7 @@ int nfs40_walk_client_list(struct nfs_cl
* way that a SETCLIENTID_CONFIRM to pos can succeed is
* if new and pos point to the same server:
*/
+found:
atomic_inc(&pos->cl_count);
spin_unlock(&nn->nfs_client_lock);
@@ -571,6 +579,7 @@ int nfs40_walk_client_list(struct nfs_cl
case 0:
nfs4_swap_callback_idents(pos, new);
pos->cl_confirm = new->cl_confirm;
+ nfs_mark_client_ready(pos, NFS_CS_READY);
prev = NULL;
*result = pos;