On 8/3/19 7:40 AM, Trond Myklebust wrote:
> John Hubbard reports seeing the following stack trace:
>
> nfs4_do_reclaim
> rcu_read_lock /* we are now in_atomic() and must not sleep */
> nfs4_purge_state_owners
> nfs4_free_state_owner
> nfs4_destroy_seqid_counter
> rpc_destroy_wait_queue
> cancel_delayed_work_sync
> __cancel_work_timer
> __flush_work
> start_flush_work
> might_sleep:
> (kernel/workqueue.c:2975: BUG)
>
> The solution is to separate out the freeing of the state owners
> from nfs4_purge_state_owners(), and perform that outside the atomic
> context.
>
All better now--this definitely fixes it. I can reboot the server, and
of course that backtrace is gone. Then the client mounts hang, so I do
a mount -a -o remount, and after about 1 minute, the client mounts
start working again, with no indication of problems. I assume that the
pause is by design--timing out somewhere, to recover from the server
going missing for a while. If so, then all is well.
thanks,
--
John Hubbard
NVIDIA
> Reported-by: John Hubbard <jhubbard@xxxxxxxxxx>
> Fixes: 0aaaf5c424c7f ("NFS: Cache state owners after files are closed")
> Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
> ---
> fs/nfs/nfs4_fs.h | 3 ++-
> fs/nfs/nfs4client.c | 5 ++++-
> fs/nfs/nfs4state.c | 27 ++++++++++++++++++++++-----
> 3 files changed, 28 insertions(+), 7 deletions(-)
>
> diff --git a/fs/nfs/nfs4_fs.h b/fs/nfs/nfs4_fs.h
> index d778dad9a75e..3564da1ba8a1 100644
> --- a/fs/nfs/nfs4_fs.h
> +++ b/fs/nfs/nfs4_fs.h
> @@ -465,7 +465,8 @@ static inline void nfs4_schedule_session_recovery(struct nfs4_session *session,
>
> extern struct nfs4_state_owner *nfs4_get_state_owner(struct nfs_server *, const struct cred *, gfp_t);
> extern void nfs4_put_state_owner(struct nfs4_state_owner *);
> -extern void nfs4_purge_state_owners(struct nfs_server *);
> +extern void nfs4_purge_state_owners(struct nfs_server *, struct list_head *);
> +extern void nfs4_free_state_owners(struct list_head *head);
> extern struct nfs4_state * nfs4_get_open_state(struct inode *, struct nfs4_state_owner *);
> extern void nfs4_put_open_state(struct nfs4_state *);
> extern void nfs4_close_state(struct nfs4_state *, fmode_t);
> diff --git a/fs/nfs/nfs4client.c b/fs/nfs/nfs4client.c
> index 616393a01c06..da6204025a2d 100644
> --- a/fs/nfs/nfs4client.c
> +++ b/fs/nfs/nfs4client.c
> @@ -758,9 +758,12 @@ int nfs41_walk_client_list(struct nfs_client *new,
>
> static void nfs4_destroy_server(struct nfs_server *server)
> {
> + LIST_HEAD(freeme);
> +
> nfs_server_return_all_delegations(server);
> unset_pnfs_layoutdriver(server);
> - nfs4_purge_state_owners(server);
> + nfs4_purge_state_owners(server, &freeme);
> + nfs4_free_state_owners(&freeme);
> }
>
> /*
> diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
> index d03b9cf42bd0..a4e866b2b43b 100644
> --- a/fs/nfs/nfs4state.c
> +++ b/fs/nfs/nfs4state.c
> @@ -624,24 +624,39 @@ void nfs4_put_state_owner(struct nfs4_state_owner *sp)
> /**
> * nfs4_purge_state_owners - Release all cached state owners
> * @server: nfs_server with cached state owners to release
> + * @head: resulting list of state owners
> *
> * Called at umount time. Remaining state owners will be on
> * the LRU with ref count of zero.
> + * Note that the state owners are not freed, but are added
> + * to the list @head, which can later be used as an argument
> + * to nfs4_free_state_owners.
> */
> -void nfs4_purge_state_owners(struct nfs_server *server)
> +void nfs4_purge_state_owners(struct nfs_server *server, struct list_head *head)
> {
> struct nfs_client *clp = server->nfs_client;
> struct nfs4_state_owner *sp, *tmp;
> - LIST_HEAD(doomed);
>
> spin_lock(&clp->cl_lock);
> list_for_each_entry_safe(sp, tmp, &server->state_owners_lru, so_lru) {
> - list_move(&sp->so_lru, &doomed);
> + list_move(&sp->so_lru, head);
> nfs4_remove_state_owner_locked(sp);
> }
> spin_unlock(&clp->cl_lock);
> +}
>
> - list_for_each_entry_safe(sp, tmp, &doomed, so_lru) {
> +/**
> + * nfs4_purge_state_owners - Release all cached state owners
> + * @head: resulting list of state owners
> + *
> + * Frees a list of state owners that was generated by
> + * nfs4_purge_state_owners
> + */
> +void nfs4_free_state_owners(struct list_head *head)
> +{
> + struct nfs4_state_owner *sp, *tmp;
> +
> + list_for_each_entry_safe(sp, tmp, head, so_lru) {
> list_del(&sp->so_lru);
> nfs4_free_state_owner(sp);
> }
> @@ -1865,12 +1880,13 @@ static int nfs4_do_reclaim(struct nfs_client *clp, const struct nfs4_state_recov
> struct nfs4_state_owner *sp;
> struct nfs_server *server;
> struct rb_node *pos;
> + LIST_HEAD(freeme);
> int status = 0;
>
> restart:
> rcu_read_lock();
> list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link) {
> - nfs4_purge_state_owners(server);
> + nfs4_purge_state_owners(server, &freeme);
> spin_lock(&clp->cl_lock);
> for (pos = rb_first(&server->state_owners);
> pos != NULL;
> @@ -1899,6 +1915,7 @@ static int nfs4_do_reclaim(struct nfs_client *clp, const struct nfs4_state_recov
> spin_unlock(&clp->cl_lock);
> }
> rcu_read_unlock();
> + nfs4_free_state_owners(&freeme);
> return 0;
> }
>
>
