* [PATCH v4.14-stable v2] nfs: fix a deadlock in nfs client initialization
@ 2019-01-24 7:00 Qian Lu
2019-01-24 17:51 ` Greg KH
0 siblings, 1 reply; 2+ messages in thread
From: Qian Lu @ 2019-01-24 7:00 UTC (permalink / raw)
To: gregkh; +Cc: stable, Scott Mayhew, Anna Schumaker, Qian Lu
From: Scott Mayhew <smayhew@redhat.com>
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;
--
2.15.3.AMZN
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH v4.14-stable v2] nfs: fix a deadlock in nfs client initialization
2019-01-24 7:00 [PATCH v4.14-stable v2] nfs: fix a deadlock in nfs client initialization Qian Lu
@ 2019-01-24 17:51 ` Greg KH
0 siblings, 0 replies; 2+ messages in thread
From: Greg KH @ 2019-01-24 17:51 UTC (permalink / raw)
To: Qian Lu; +Cc: stable, Scott Mayhew, Anna Schumaker
On Wed, Jan 23, 2019 at 11:00:24PM -0800, Qian Lu wrote:
> From: Scott Mayhew <smayhew@redhat.com>
>
> 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(-)
You forgot to mention the sha1 of the commit :(
I dug it up this time...
greg k-h
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