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authorScott Mayhew <smayhew@redhat.com>2017-12-05 21:55:44 +0300
committerAnna Schumaker <Anna.Schumaker@Netapp.com>2017-12-15 22:31:49 +0300
commitc156618e15101a9cc8c815108fec0300a0ec6637 (patch)
treeaa9384520ea1a224d5be11bfe2614f03580791d0 /fs/nfs/client.c
parenteb5b46faa693470681ec7c28cc2436edd1571198 (diff)
downloadlinux-c156618e15101a9cc8c815108fec0300a0ec6637.tar.xz
nfs: fix a deadlock in nfs client initialization
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>
Diffstat (limited to 'fs/nfs/client.c')
-rw-r--r--fs/nfs/client.c11
1 files changed, 11 insertions, 0 deletions
diff --git a/fs/nfs/client.c b/fs/nfs/client.c
index 0ac2fb1c6b63..b9129e2befea 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) {
+ refcount_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;