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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/nfs4client.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/nfs4client.c')
-rw-r--r--fs/nfs/nfs4client.c17
1 files changed, 13 insertions, 4 deletions
diff --git a/fs/nfs/nfs4client.c b/fs/nfs/nfs4client.c
index 12bbab0becb4..65a7e5da508c 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:
refcount_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;