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Commit 55a67399 authored by Trond Myklebust's avatar Trond Myklebust
Browse files

NFSv4.1: Fix the callback 'highest_used_slotid' behaviour 



Currently, there is no guarantee that we will call nfs4_cb_take_slot() even
though nfs4_callback_compound() will consistently call
nfs4_cb_free_slot() provided the cb_process_state has set the 'clp' field.
The result is that we can trigger the BUG_ON() upon the next call to
nfs4_cb_take_slot().

This patch fixes the above problem by using the slot id that was taken in
the CB_SEQUENCE operation as a flag for whether or not we need to call
nfs4_cb_free_slot().
It also fixes an atomicity problem: we need to set tbl->highest_used_slotid
atomically with the check for NFS4_SESSION_DRAINING, otherwise we end up
racing with the various tests in nfs4_begin_drain_session().

Cc: stable@kernel.org [2.6.38+]
Signed-off-by: default avatarTrond Myklebust <Trond.Myklebust@netapp.com>
parent 9af7db32

fs/nfs/callback.h

+1 −1
Original line number Diff line number Diff line
@@ -38,6 +38,7 @@ enum nfs4_callback_opnum { 
struct cb_process_state {

	__be32			drc_status;

	struct nfs_client	*clp;

	int			slotid;

};



struct cb_compound_hdr_arg {
@@ -166,7 +167,6 @@ extern unsigned nfs4_callback_layoutrecall( 
	void *dummy, struct cb_process_state *cps);



extern void nfs4_check_drain_bc_complete(struct nfs4_session *ses);

extern void nfs4_cb_take_slot(struct nfs_client *clp);



struct cb_devicenotifyitem {

	uint32_t		cbd_notify_type;

fs/nfs/callback_proc.c

+14 −6
Original line number Diff line number Diff line
@@ -348,7 +348,7 @@ validate_seqid(struct nfs4_slot_table *tbl, struct cb_sequenceargs * args) 
	/* Normal */

	if (likely(args->csa_sequenceid == slot->seq_nr + 1)) {

		slot->seq_nr++;

		return htonl(NFS4_OK);

		goto out_ok;

	}



	/* Replay */
@@ -367,11 +367,14 @@ validate_seqid(struct nfs4_slot_table *tbl, struct cb_sequenceargs * args) 
	/* Wraparound */

	if (args->csa_sequenceid == 1 && (slot->seq_nr + 1) == 0) {

		slot->seq_nr = 1;

		return htonl(NFS4_OK);

		goto out_ok;

	}



	/* Misordered request */

	return htonl(NFS4ERR_SEQ_MISORDERED);

out_ok:

	tbl->highest_used_slotid = args->csa_slotid;

	return htonl(NFS4_OK);

}



/*
@@ -433,26 +436,32 @@ __be32 nfs4_callback_sequence(struct cb_sequenceargs *args, 
			      struct cb_sequenceres *res,

			      struct cb_process_state *cps)

{

	struct nfs4_slot_table *tbl;

	struct nfs_client *clp;

	int i;

	__be32 status = htonl(NFS4ERR_BADSESSION);



	cps->clp = NULL;



	clp = nfs4_find_client_sessionid(args->csa_addr, &args->csa_sessionid);

	if (clp == NULL)

		goto out;



	tbl = &clp->cl_session->bc_slot_table;



	spin_lock(&tbl->slot_tbl_lock);

	/* state manager is resetting the session */

	if (test_bit(NFS4_SESSION_DRAINING, &clp->cl_session->session_state)) {

		status = NFS4ERR_DELAY;

		spin_unlock(&tbl->slot_tbl_lock);

		status = htonl(NFS4ERR_DELAY);

		goto out;

	}



	status = validate_seqid(&clp->cl_session->bc_slot_table, args);

	spin_unlock(&tbl->slot_tbl_lock);

	if (status)

		goto out;



	cps->slotid = args->csa_slotid;



	/*

	 * Check for pending referring calls.  If a match is found, a

	 * related callback was received before the response to the original
@@ -469,7 +478,6 @@ __be32 nfs4_callback_sequence(struct cb_sequenceargs *args, 
	res->csr_slotid = args->csa_slotid;

	res->csr_highestslotid = NFS41_BC_MAX_CALLBACKS - 1;

	res->csr_target_highestslotid = NFS41_BC_MAX_CALLBACKS - 1;

	nfs4_cb_take_slot(clp);



out:

	cps->clp = clp; /* put in nfs4_callback_compound */

fs/nfs/callback_xdr.c

+7 −17
Original line number Diff line number Diff line
@@ -754,26 +754,15 @@ static void nfs4_callback_free_slot(struct nfs4_session *session) 
	 * Let the state manager know callback processing done.

	 * A single slot, so highest used slotid is either 0 or -1

	 */

	tbl->highest_used_slotid--;

	tbl->highest_used_slotid = -1;

	nfs4_check_drain_bc_complete(session);

	spin_unlock(&tbl->slot_tbl_lock);

}



static void nfs4_cb_free_slot(struct nfs_client *clp)

static void nfs4_cb_free_slot(struct cb_process_state *cps)

{

	if (clp && clp->cl_session)

		nfs4_callback_free_slot(clp->cl_session);

}



/* A single slot, so highest used slotid is either 0 or -1 */

void nfs4_cb_take_slot(struct nfs_client *clp)

{

	struct nfs4_slot_table *tbl = &clp->cl_session->bc_slot_table;



	spin_lock(&tbl->slot_tbl_lock);

	tbl->highest_used_slotid++;

	BUG_ON(tbl->highest_used_slotid != 0);

	spin_unlock(&tbl->slot_tbl_lock);

	if (cps->slotid != -1)

		nfs4_callback_free_slot(cps->clp->cl_session);

}



#else /* CONFIG_NFS_V4_1 */
@@ -784,7 +773,7 @@ preprocess_nfs41_op(int nop, unsigned int op_nr, struct callback_op **op) 
	return htonl(NFS4ERR_MINOR_VERS_MISMATCH);

}



static void nfs4_cb_free_slot(struct nfs_client *clp)

static void nfs4_cb_free_slot(struct cb_process_state *cps)

{

}

#endif /* CONFIG_NFS_V4_1 */
@@ -866,6 +855,7 @@ static __be32 nfs4_callback_compound(struct svc_rqst *rqstp, void *argp, void *r 
	struct cb_process_state cps = {

		.drc_status = 0,

		.clp = NULL,

		.slotid = -1,

	};

	unsigned int nops = 0;
@@ -906,7 +896,7 @@ static __be32 nfs4_callback_compound(struct svc_rqst *rqstp, void *argp, void *r 


	*hdr_res.status = status;

	*hdr_res.nops = htonl(nops);

	nfs4_cb_free_slot(cps.clp);

	nfs4_cb_free_slot(&cps);

	nfs_put_client(cps.clp);

	dprintk("%s: done, status = %u\n", __func__, ntohl(status));

	return rpc_success;