NFS: Fix the locking in nfs4_callback_getattr

The delegation is protected by RCU now, so we need to replace the
nfsi->rwsem protection with an rcu protected section.

Reported-by: Fred Isaman <iisaman@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

diff --git a/fs/nfs/callback_proc.c b/fs/nfs/callback_proc.c
index 7445dd0ae3f31b297ad117c05d34dc52cc974c07..930d10fecdaff8632dc35869c3695fc8397e8d7a 100644 (file)
--- a/fs/nfs/callback_proc.c
+++ b/fs/nfs/callback_proc.c
@@ -37,8 +37,8 @@ __be32 nfs4_callback_getattr(struct cb_getattrargs *args, struct cb_getattrres *
        if (inode == NULL)
                goto out_putclient;
        nfsi = NFS_I(inode);
-       down_read(&nfsi->rwsem);
-       delegation = nfsi->delegation;
+       rcu_read_lock();
+       delegation = rcu_dereference(nfsi->delegation);
        if (delegation == NULL || (delegation->type & FMODE_WRITE) == 0)
                goto out_iput;
        res->size = i_size_read(inode);
@@ -53,7 +53,7 @@ __be32 nfs4_callback_getattr(struct cb_getattrargs *args, struct cb_getattrres *
                args->bitmap[1];
        res->status = 0;
 out_iput:
-       up_read(&nfsi->rwsem);
+       rcu_read_unlock();
        iput(inode);
 out_putclient:
        nfs_put_client(clp);