NFS: use cond_resched() when restarting walk of delegation list.

In three places we walk the list of delegations for an nfs_client
until an interesting one is found, then we act of that delegation
and restart the walk.

New delegations are added to the end of a list and the interesting
delegations are usually old, so in many case we won't repeat
a long walk over and over again, but it is possible - particularly if
the first server in the list has a large number of uninteresting
delegations.

In each cache the work done on interesting delegations will often
complete without sleeping, so this could loop many times without
giving up the CPU.

So add a cond_resched() at an appropriate point to avoid hogging the
CPU for too long.

Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

diff --git a/fs/nfs/delegation.c b/fs/nfs/delegation.c
index b9cd3864335b299670896b5ff9a129184256476e..c454532b6f03f276df0aa37821fe10a72349a4aa 100644 (file)
--- a/fs/nfs/delegation.c
+++ b/fs/nfs/delegation.c
@@ -508,6 +508,7 @@ restart:
                        err = nfs_end_delegation_return(inode, delegation, 0);
                        iput(inode);
                        nfs_sb_deactive(server->super);
+                       cond_resched();
                        if (!err)
                                goto restart;
                        set_bit(NFS4CLNT_DELEGRETURN, &clp->cl_state);
@@ -904,6 +905,7 @@ restart:
                        }
                        iput(inode);
                        nfs_sb_deactive(server->super);
+                       cond_resched();
                        goto restart;
                }
        }
@@ -1020,6 +1022,7 @@ restart:
                        }
                        iput(inode);
                        nfs_sb_deactive(server->super);
+                       cond_resched();
                        goto restart;
                }
        }