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authorScott Mayhew <smayhew@redhat.com>2017-12-05 13:55:44 -0500
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-01-26 09:37:07 +0100
commit53818c7644887757fb9181c988e0fd4c17a9c1cb (patch)
treeceb401963e12f183f5c6a8cdbec1598756e2f050
parent696ce77bba5ca4e486a9b6ed4d27a41fcd2f7169 (diff)
download96b-common-53818c7644887757fb9181c988e0fd4c17a9c1cb.tar.gz
nfs: fix a deadlock in nfs client initialization
commit c156618e15101a9cc8c815108fec0300a0ec6637 upstream. 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 --------- --------- 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> Signed-off-by: Qian Lu <luqia@amazon.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--fs/nfs/client.c11
-rw-r--r--fs/nfs/nfs4client.c17
2 files changed, 24 insertions, 4 deletions
diff --git a/fs/nfs/client.c b/fs/nfs/client.c
index 22880ef6d8dd..7d6ddfd60271 100644
--- a/fs/nfs/client.c
+++ b/fs/nfs/client.c
@@ -291,12 +291,23 @@ static struct nfs_client *nfs_match_client(const struct nfs_client_initdata *dat
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;
diff --git a/fs/nfs/nfs4client.c b/fs/nfs/nfs4client.c
index fed9c8005c17..8f96f6548dc8 100644
--- a/fs/nfs/nfs4client.c
+++ b/fs/nfs/nfs4client.c
@@ -404,15 +404,19 @@ struct nfs_client *nfs4_init_client(struct nfs_client *clp,
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);
clear_bit(NFS_CS_TSM_POSSIBLE, &clp->cl_flags);
return old;
@@ -539,6 +543,9 @@ int nfs40_walk_client_list(struct nfs_client *new,
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;
@@ -559,6 +566,7 @@ int nfs40_walk_client_list(struct nfs_client *new,
* 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);
@@ -572,6 +580,7 @@ int nfs40_walk_client_list(struct nfs_client *new,
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;