NFSv4: Avoid unnecessary scans of filesystems for returning delegations

The amount of looping through the list of delegations is occasionally
leading to soft lockups. If the state manager was asked to return
delegations asynchronously, it should only scan those filesystems that
hold delegations that need to be returned.

Fixes: af3b61bf6131 ("NFSv4: Clean up nfs_client_return_marked_delegations()")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

diff --git a/fs/nfs/delegation.c b/fs/nfs/delegation.c
index df77d68d9ff99192524e43566c7cc759801ba1d2..d1f5e497729c3b5fbdb6b4dbfa601017c9d7bf35 100644 (file)
--- a/fs/nfs/delegation.c
+++ b/fs/nfs/delegation.c
@@ -79,6 +79,7 @@ static void nfs_mark_return_delegation(struct nfs_server *server,
                                       struct nfs_delegation *delegation)
 {
        set_bit(NFS_DELEGATION_RETURN, &delegation->flags);
+       set_bit(NFS4SERV_DELEGRETURN, &server->delegation_flags);
        set_bit(NFS4CLNT_DELEGRETURN, &server->nfs_client->cl_state);
 }
 
@@ -608,6 +609,9 @@ static int nfs_server_return_marked_delegations(struct nfs_server *server,
        struct nfs_delegation *place_holder_deleg = NULL;
        int err = 0;
 
+       if (!test_and_clear_bit(NFS4SERV_DELEGRETURN,
+                               &server->delegation_flags))
+               return 0;
 restart:
        /*
         * To avoid quadratic looping we hold a reference
@@ -659,6 +663,7 @@ restart:
                cond_resched();
                if (!err)
                        goto restart;
+               set_bit(NFS4SERV_DELEGRETURN, &server->delegation_flags);
                set_bit(NFS4CLNT_DELEGRETURN, &server->nfs_client->cl_state);
                goto out;
        }

diff --git a/include/linux/nfs_fs_sb.h b/include/linux/nfs_fs_sb.h
index f00bfcee7120e8aa0c337fbb72188e77116fb9a5..4e9ad6f6e90731e99b48783255641d2354c9e267 100644 (file)
--- a/include/linux/nfs_fs_sb.h
+++ b/include/linux/nfs_fs_sb.h
@@ -250,6 +250,8 @@ struct nfs_server {
        struct list_head        ss_copies;
        struct list_head        ss_src_copies;
 
+       unsigned long           delegation_flags;
+#define NFS4SERV_DELEGRETURN           (1)
        unsigned long           delegation_gen;
        unsigned long           mig_gen;
        unsigned long           mig_status;