nfsd: use i_wrlock instead of rcu for nfsdfs i_private

synchronize_rcu() gets called multiple times each time a client is
destroyed.  If the laundromat thread has a lot of clients to destroy,
the delay can be noticeable.  This was causing pynfs test RENEW3 to
fail.

We could embed an rcu_head in each inode and do the kref_put in an rcu
callback.  But simplest is just to take a lock here.

(I also wonder if the laundromat thread would be better replaced by a
bunch of scheduled work or timers or something.)

Signed-off-by: J. Bruce Fields <bfields@redhat.com>

diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index 928a0b2c05dc4284eaaa1e2f735458f57cec4e18..b14f825c62fecaa09dfb622a6f0d04cdf4e887e2 100644 (file)
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -1215,11 +1215,9 @@ static void clear_ncl(struct inode *inode)
        struct nfsdfs_client *ncl = inode->i_private;
 
        inode->i_private = NULL;
-       synchronize_rcu();
        kref_put(&ncl->cl_ref, ncl->cl_release);
 }
 
-
 static struct nfsdfs_client *__get_nfsdfs_client(struct inode *inode)
 {
        struct nfsdfs_client *nc = inode->i_private;
@@ -1233,9 +1231,9 @@ struct nfsdfs_client *get_nfsdfs_client(struct inode *inode)
 {
        struct nfsdfs_client *nc;
 
-       rcu_read_lock();
+       inode_lock_shared(inode);
        nc = __get_nfsdfs_client(inode);
-       rcu_read_unlock();
+       inode_unlock_shared(inode);
        return nc;
 }
 /* from __rpc_unlink */