Commit c77e2283 authored by Trond Myklebust's avatar Trond Myklebust
Browse files

NFSv4: Fix a potential sleep while atomic in nfs4_do_reclaim() 



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.

Reported-by: default avatarJohn Hubbard <jhubbard@nvidia.com>
Fixes: 0aaaf5c4 ("NFS: Cache state owners after files are closed")
Signed-off-by: default avatarTrond Myklebust <trond.myklebust@hammerspace.com>
parent e3c8dc76

fs/nfs/nfs4_fs.h

+2 −1
Original line number Diff line number Diff line
@@ -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);

fs/nfs/nfs4client.c

+4 −1
Original line number Diff line number Diff line
@@ -758,9 +758,12 @@ out: 


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);

}



/*

fs/nfs/nfs4state.c

+22 −5
Original line number Diff line number Diff line
@@ -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 @@ restart: 
		spin_unlock(&clp->cl_lock);

	}

	rcu_read_unlock();

	nfs4_free_state_owners(&freeme);

	return 0;

}

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