On Wed, Jan 23, 2019 at 10:05:26AM +0000, Lu, Qian wrote:

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

---

fs/nfs/client.c     | 11 +++++++++++ fs/nfs/nfs4client.c | 17 +++++++++++++---- 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;

All of the tabs were turned into spaces here and this patch can not be applied :(

Please fix up and resend.

thanks,

greg k-h