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Commit ea028ac9 authored by Andy Adamson's avatar Andy Adamson Committed by Trond Myklebust
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nfs41: nfs41: fix state manager deadlock in session reset 



If the session is reset during state recovery, the state manager thread can
sleep on the slot_tbl_waitq causing a deadlock.

Add a completion framework to the session.  Have the state manager thread set
a new session state (NFS4CLNT_SESSION_DRAINING) and wait for the session slot
table to drain.

Signal the state manager thread in nfs41_sequence_free_slot when the
NFS4CLNT_SESSION_DRAINING bit is set and the session is drained.

Reported-by: default avatarTrond Myklebust <trond@netapp.com>
Signed-off-by: default avatarAndy Adamson <andros@netapp.com>
Signed-off-by: default avatarTrond Myklebust <Trond.Myklebust@netapp.com>
parent 05f0d236

fs/nfs/nfs4_fs.h

+1 −0
Original line number Diff line number Diff line
@@ -45,6 +45,7 @@ enum nfs4_client_state { 
	NFS4CLNT_RECLAIM_NOGRACE,

	NFS4CLNT_DELEGRETURN,

	NFS4CLNT_SESSION_RESET,

	NFS4CLNT_SESSION_DRAINING,

};



/*

fs/nfs/nfs4proc.c

+17 −9
Original line number Diff line number Diff line
@@ -361,6 +361,16 @@ void nfs41_sequence_free_slot(const struct nfs_client *clp, 
	}

	nfs4_free_slot(tbl, res->sr_slotid);

	res->sr_slotid = NFS4_MAX_SLOT_TABLE;



	/* Signal state manager thread if session is drained */

	if (test_bit(NFS4CLNT_SESSION_DRAINING, &clp->cl_state)) {

		spin_lock(&tbl->slot_tbl_lock);

		if (tbl->highest_used_slotid == -1) {

			dprintk("%s COMPLETE: Session Drained\n", __func__);

			complete(&clp->cl_session->complete);

		}

		spin_unlock(&tbl->slot_tbl_lock);

	}

}



static void nfs41_sequence_done(struct nfs_client *clp,
@@ -457,15 +467,11 @@ static int nfs41_setup_sequence(struct nfs4_session *session, 


	spin_lock(&tbl->slot_tbl_lock);

	if (test_bit(NFS4CLNT_SESSION_RESET, &session->clp->cl_state)) {

		if (tbl->highest_used_slotid != -1) {

			rpc_sleep_on(&tbl->slot_tbl_waitq, task, NULL);

			spin_unlock(&tbl->slot_tbl_lock);

			dprintk("<-- %s: Session reset: draining\n", __func__);

			return -EAGAIN;

		}



		/* The slot table is empty; start the reset thread */

		dprintk("%s Session Reset\n", __func__);

		/*

		 * The state manager will wait until the slot table is empty.

		 * Schedule the reset thread

		 */

		dprintk("%s Schedule Session Reset\n", __func__);

		rpc_sleep_on(&tbl->slot_tbl_waitq, task, NULL);

		nfs4_schedule_state_manager(session->clp);

		spin_unlock(&tbl->slot_tbl_lock);
@@ -4506,6 +4512,7 @@ static int nfs4_reset_slot_tables(struct nfs4_session *session) 
			1);

	if (status)

		return status;

	init_completion(&session->complete);



	status = nfs4_reset_slot_table(&session->bc_slot_table,

			session->bc_attrs.max_reqs,
@@ -4608,6 +4615,7 @@ struct nfs4_session *nfs4_alloc_session(struct nfs_client *clp) 
	 * nfs_client struct

	 */

	clp->cl_cons_state = NFS_CS_SESSION_INITING;

	init_completion(&session->complete);



	tbl = &session->fc_slot_table;

	spin_lock_init(&tbl->slot_tbl_lock);

fs/nfs/nfs4state.c

+15 −0
Original line number Diff line number Diff line
@@ -1181,8 +1181,23 @@ static void nfs4_session_recovery_handle_error(struct nfs_client *clp, int err) 


static int nfs4_reset_session(struct nfs_client *clp)

{

	struct nfs4_session *ses = clp->cl_session;

	struct nfs4_slot_table *tbl = &ses->fc_slot_table;

	int status;



	INIT_COMPLETION(ses->complete);

	spin_lock(&tbl->slot_tbl_lock);

	if (tbl->highest_used_slotid != -1) {

		set_bit(NFS4CLNT_SESSION_DRAINING, &clp->cl_state);

		spin_unlock(&tbl->slot_tbl_lock);

		status = wait_for_completion_interruptible(&ses->complete);

		clear_bit(NFS4CLNT_SESSION_DRAINING, &clp->cl_state);

		if (status) /* -ERESTARTSYS */

			goto out;

	} else {

		spin_unlock(&tbl->slot_tbl_lock);

	}



	status = nfs4_proc_destroy_session(clp->cl_session);

	if (status && status != -NFS4ERR_BADSESSION &&

	    status != -NFS4ERR_DEADSESSION) {

include/linux/nfs_fs_sb.h

+1 −0
Original line number Diff line number Diff line
@@ -209,6 +209,7 @@ struct nfs4_session { 
	unsigned long			session_state;

	u32				hash_alg;

	u32				ssv_len;

	struct completion		complete;



	/* The fore and back channel */

	struct nfs4_channel_attrs	fc_attrs;