NFS: Add an asynchronous delegreturn operation for use in nfs_clear_inode

Otherwise, there is a potential deadlock if the last dput() from an NFSv4
close() or other asynchronous operation leads to nfs_clear_inode calling
the synchronous delegreturn.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 13 insertions, 9 deletions

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 89efbcd6fd53..5c189bd57eb2 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -2991,7 +2991,7 @@ static const struct rpc_call_ops nfs4_delegreturn_ops = {
         .rpc_release = nfs4_delegreturn_release,
 };
 
-static int _nfs4_proc_delegreturn(struct inode *inode, struct rpc_cred *cred, const nfs4_stateid *stateid)
+static int _nfs4_proc_delegreturn(struct inode *inode, struct rpc_cred *cred, const nfs4_stateid *stateid, int issync)
 {
         struct nfs4_delegreturndata *data;
         struct nfs_server *server = NFS_SERVER(inode);
@@ -3006,7 +3006,7 @@ static int _nfs4_proc_delegreturn(struct inode *inode, struct rpc_cred *cred, co
                 .callback_ops = &nfs4_delegreturn_ops,
                 .flags = RPC_TASK_ASYNC,
         };
-        int status;
+        int status = 0;
 
         data = kmalloc(sizeof(*data), GFP_KERNEL);
         if (data == NULL)
@@ -3028,23 +3028,27 @@ static int _nfs4_proc_delegreturn(struct inode *inode, struct rpc_cred *cred, co
         task = rpc_run_task(&task_setup_data);
         if (IS_ERR(task))
                 return PTR_ERR(task);
+        if (!issync)
+                goto out;
         status = nfs4_wait_for_completion_rpc_task(task);
-        if (status == 0) {
-                status = data->rpc_status;
-                if (status == 0)
-                        nfs_refresh_inode(inode, &data->fattr);
-        }
+        if (status != 0)
+                goto out;
+        status = data->rpc_status;
+        if (status != 0)
+                goto out;
+        nfs_refresh_inode(inode, &data->fattr);
+out:
         rpc_put_task(task);
         return status;
 }
 
-int nfs4_proc_delegreturn(struct inode *inode, struct rpc_cred *cred, const nfs4_stateid *stateid)
+int nfs4_proc_delegreturn(struct inode *inode, struct rpc_cred *cred, const nfs4_stateid *stateid, int issync)
 {
         struct nfs_server *server = NFS_SERVER(inode);
         struct nfs4_exception exception = { };
         int err;
         do {
-                err = _nfs4_proc_delegreturn(inode, cred, stateid);
+                err = _nfs4_proc_delegreturn(inode, cred, stateid, issync);
                 switch (err) {
                         case -NFS4ERR_STALE_STATEID:
                         case -NFS4ERR_EXPIRED: