NFSv4: Ensure that file unlock requests don't conflict with state recovery

The unlock path is currently failing to take the nfs_client->cl_sem read
lock, and hence the recovery path may see locks disappear from underneath
it.
Also ensure that it takes the nfs_inode->rwsem read lock so that it there
is no conflict with delegation recalls.

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

1 files changed, 4 insertions, 0 deletions

diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
index beade5570b56..16c9fbdf97b4 100644
--- a/fs/nfs/nfs4state.c
+++ b/fs/nfs/nfs4state.c
@@ -849,9 +849,11 @@ static int nfs4_state_mark_reclaim_nograce(struct nfs_client *clp, struct nfs4_s
 static int nfs4_reclaim_locks(struct nfs4_state *state, const struct nfs4_state_recovery_ops *ops)
 {
         struct inode *inode = state->inode;
+        struct nfs_inode *nfsi = NFS_I(inode);
         struct file_lock *fl;
         int status = 0;
 
+        down_write(&nfsi->rwsem);
         for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
                 if (!(fl->fl_flags & (FL_POSIX|FL_FLOCK)))
                         continue;
@@ -874,8 +876,10 @@ static int nfs4_reclaim_locks(struct nfs4_state *state, const struct nfs4_state_
                                 goto out_err;
                 }
         }
+        up_write(&nfsi->rwsem);
         return 0;
 out_err:
+        up_write(&nfsi->rwsem);
         return status;
 }