Commit 28df3d15 authored by J. Bruce Fields's avatar J. Bruce Fields
Browse files

nfsd: clients don't need to break their own delegations 



We currently revoke read delegations on any write open or any operation
that modifies file data or metadata (including rename, link, and
unlink).  But if the delegation in question is the only read delegation
and is held by the client performing the operation, that's not really
necessary.

It's not always possible to prevent this in the NFSv4.0 case, because
there's not always a way to determine which client an NFSv4.0 delegation
came from.  (In theory we could try to guess this from the transport
layer, e.g., by assuming all traffic on a given TCP connection comes
from the same client.  But that's not really correct.)

In the NFSv4.1 case the session layer always tells us the client.

This patch should remove such self-conflicts in all cases where we can
reliably determine the client from the compound.

To do that we need to track "who" is performing a given (possibly
lease-breaking) file operation.  We're doing that by storing the
information in the svc_rqst and using kthread_data() to map the current
task back to a svc_rqst.

Signed-off-by: default avatarJ. Bruce Fields <bfields@redhat.com>
parent 52782c92

Documentation/filesystems/locking.rst

+2 −0
Original line number Diff line number Diff line
@@ -425,6 +425,7 @@ prototypes:: 
	int (*lm_grant)(struct file_lock *, struct file_lock *, int);

	void (*lm_break)(struct file_lock *); /* break_lease callback */

	int (*lm_change)(struct file_lock **, int);

	bool (*lm_breaker_owns_lease)(struct file_lock *);



locking rules:
@@ -435,6 +436,7 @@ lm_notify: yes yes no 
lm_grant:		no		no			no

lm_break:		yes		no			no

lm_change		yes		no			no

lm_breaker_owns_lease:	no		no			no

==========		=============	=================	=========



buffer_head

fs/locks.c

+3 −0
Original line number Diff line number Diff line
@@ -1557,6 +1557,9 @@ static bool leases_conflict(struct file_lock *lease, struct file_lock *breaker) 
{

	bool rc;



	if (lease->fl_lmops->lm_breaker_owns_lease

			&& lease->fl_lmops->lm_breaker_owns_lease(lease))

		return false;

	if ((breaker->fl_flags & FL_LAYOUT) != (lease->fl_flags & FL_LAYOUT)) {

		rc = false;

		goto trace;

fs/nfsd/nfs4proc.c

+2 −0
Original line number Diff line number Diff line
@@ -2302,6 +2302,8 @@ nfsd4_proc_compound(struct svc_rqst *rqstp) 
	}

	check_if_stalefh_allowed(args);



	rqstp->rq_lease_breaker = (void **)&cstate->clp;



	trace_nfsd_compound(rqstp, args->opcnt);

	while (!status && resp->opcnt < args->opcnt) {

		op = &args->ops[resp->opcnt++];

fs/nfsd/nfs4state.c

+14 −0
Original line number Diff line number Diff line
@@ -4579,6 +4579,19 @@ nfsd_break_deleg_cb(struct file_lock *fl) 
	return ret;

}



static bool nfsd_breaker_owns_lease(struct file_lock *fl)

{

	struct nfs4_delegation *dl = fl->fl_owner;

	struct svc_rqst *rqst;

	struct nfs4_client *clp;



	if (!i_am_nfsd())

		return NULL;

	rqst = kthread_data(current);

	clp = *(rqst->rq_lease_breaker);

	return dl->dl_stid.sc_client == clp;

}



static int

nfsd_change_deleg_cb(struct file_lock *onlist, int arg,

		     struct list_head *dispose)
@@ -4590,6 +4603,7 @@ nfsd_change_deleg_cb(struct file_lock *onlist, int arg, 
}



static const struct lock_manager_operations nfsd_lease_mng_ops = {

	.lm_breaker_owns_lease = nfsd_breaker_owns_lease,

	.lm_break = nfsd_break_deleg_cb,

	.lm_change = nfsd_change_deleg_cb,

};

fs/nfsd/nfsd.h

+2 −0
Original line number Diff line number Diff line
@@ -88,6 +88,8 @@ int nfsd_pool_stats_release(struct inode *, struct file *); 


void		nfsd_destroy(struct net *net);



bool		i_am_nfsd(void);



struct nfsdfs_client {

	struct kref cl_ref;

	void (*cl_release)(struct kref *kref);

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