Date:	Mon, 1 Apr 2013 21:50:44 -0400
From:	"J. Bruce Fields" <bfields@...ldses.org>
To:	Yanchuan Nian <ycnian@...il.com>
Cc:	linux-kernel@...r.kernel.org, linux-nfs@...r.kernel.org
Subject: Re: [PATCH v2] nfsd: fix bug on nfs4 stateid deallocation

On Wed, Mar 13, 2013 at 11:04:54PM +0800, Yanchuan Nian wrote:
> 2013/3/11 J. Bruce Fields <bfields@...ldses.org>
> 
> > On Mon, Mar 11, 2013 at 08:46:14AM +0800, ycnian@...il.com wrote:
> > > NFS4_OO_PURGE_CLOSE is not handled properly. To avoid memory leak, nfs4
> > > stateid which is pointed by oo_last_closed_stid is freed in
> > nfsd4_close(),
> > > but NFS4_OO_PURGE_CLOSE isn't cleared meanwhile. So the stateid released
> > in
> > > THIS close procedure may be freed immediately in the coming encoding
> > function.
> >
> > OK, makes sense.  This code is confusing, I wonder if there's some way
> > we could make it simpler.
> >
> 
> The only purpose of NFS4_OO_PURGE_CLOSE is to decide whether the stateid
> pointed by last-closed-stateid should be freed or not. I wonder if this
> flag is necessary. oo_last_closed_stid is set only in CLOSE, so in other
> procedures, if the pointer is not NULL, it must be set in previous
> procedure, we can free it directly. In CLOSE procedure, we also free it
> directly before asigning the new released stateid to it in nfsd4_close(),
> and then we can ignore it in nfsd4_encode_close(). What do you think?

Yeah, something like that would be simpler, I think.  Maybe the
following?  (On top of your patch.)

> I don't quite understand the difficulties in CLOSE retransmission. RFC3530
> suggests we deallocate the stateid in next validly sequenced request. If we
> don't do so, what will happen?

Nothing bad.  It's just that the stateid isn't useful any more past that
point, so we may as well get rid of it.  (If the client sends the close
with sequence number s, and then resends the close, we want to be able
to reply.  But once it sends another operation with sequence s+1, it's
saying that it's received the answer to the close now.  And any further
attempt to send something with sequence number s would fail.)

> I don't see this suggestion in RFC5661, and
> the stateid is deallocated directly in NFSv4.1, why? Thanks very much.

In 4.1 these stateowner-based sequence numbers aren't used any more.
(They're still there, but they're ignored.)  Instead 4.1 depends on the
SEQUENCE operation to provide ordering and exactly-once semantics.

--b.

commit 4e603ce0a56deeac0a83d067a863f96f0619c26d
Author: J. Bruce Fields <bfields@...hat.com>
Date:   Mon Apr 1 16:37:12 2013 -0400

    nfsd4: cleanup handling of nfsv4.0 closed stateid's
    
    Signed-off-by: J. Bruce Fields <bfields@...hat.com>

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 285a0c8..aa6e77f 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -575,7 +575,7 @@ static void unhash_openowner(struct nfs4_openowner *oo)
 	}
 }
 
-static void release_last_closed_stateid(struct nfs4_openowner *oo)
+void release_last_closed_stateid(struct nfs4_openowner *oo)
 {
 	struct nfs4_ol_stateid *s = oo->oo_last_closed_stid;
 
@@ -3760,26 +3760,6 @@ out:
 	return status;
 }
 
-void nfsd4_purge_closed_stateid(struct nfs4_stateowner *so)
-{
-	struct nfs4_openowner *oo;
-	struct nfs4_ol_stateid *s;
-
-	if (!so->so_is_open_owner)
-		return;
-	oo = openowner(so);
-	s = oo->oo_last_closed_stid;
-	if (!s)
-		return;
-	if (!(oo->oo_flags & NFS4_OO_PURGE_CLOSE)) {
-		/* Release the last_closed_stid on the next seqid bump: */
-		oo->oo_flags |= NFS4_OO_PURGE_CLOSE;
-		return;
-	}
-	oo->oo_flags &= ~NFS4_OO_PURGE_CLOSE;
-	release_last_closed_stateid(oo);
-}
-
 static void nfsd4_close_open_stateid(struct nfs4_ol_stateid *s)
 {
 	unhash_open_stateid(s);
@@ -3816,9 +3796,7 @@ nfsd4_close(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 	memcpy(&close->cl_stateid, &stp->st_stid.sc_stateid, sizeof(stateid_t));
 
 	nfsd4_close_open_stateid(stp);
-	release_last_closed_stateid(oo);
-	oo->oo_flags &= ~NFS4_OO_PURGE_CLOSE;
-	oo->oo_last_closed_stid = stp;
+	close->cl_closed_stateid = stp;
 
 	if (list_empty(&oo->oo_owner.so_stateids)) {
 		if (cstate->minorversion) {
diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index e3dc58d..2324638 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -527,6 +527,7 @@ nfsd4_decode_close(struct nfsd4_compoundargs *argp, struct nfsd4_close *close)
 {
 	DECODE_HEAD;
 
+	close->cl_closed_stateid = NULL;
 	READ_BUF(4);
 	READ32(close->cl_seqid);
 	return nfsd4_decode_stateid(argp, &close->cl_stateid);
@@ -1707,8 +1708,7 @@ static void write_cinfo(__be32 **p, struct nfsd4_change_info *c)
  * Note that we increment sequence id's here, at the last moment, so we're sure
  * we know whether the error to be returned is a sequence id mutating error.
  */
-
-static void encode_seqid_op_tail(struct nfsd4_compoundres *resp, __be32 *save, __be32 nfserr)
+static void encode_seqid_op_tail(struct nfsd4_compoundres *resp, __be32 *save, __be32 nfserr, struct nfs4_ol_stateid *close_stp)
 {
 	struct nfs4_stateowner *stateowner = resp->cstate.replay_owner;
 
@@ -1719,7 +1719,13 @@ static void encode_seqid_op_tail(struct nfsd4_compoundres *resp, __be32 *save, _
 			  (char *)resp->p - (char *)save;
 		memcpy(stateowner->so_replay.rp_buf, save,
 			stateowner->so_replay.rp_buflen);
-		nfsd4_purge_closed_stateid(stateowner);
+		if (stateowner->so_is_open_owner) {
+			struct nfs4_openowner *oo = openowner(stateowner);
+
+			release_last_closed_stateid(oo);
+			if (close_stp)
+				oo->oo_last_closed_stid = close_stp;
+		}
 	}
 }
 
@@ -2667,7 +2673,7 @@ nfsd4_encode_close(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4_c
 	if (!nfserr)
 		nfsd4_encode_stateid(resp, &close->cl_stateid);
 
-	encode_seqid_op_tail(resp, save, nfserr);
+	encode_seqid_op_tail(resp, save, nfserr, close->cl_closed_stateid);
 	return nfserr;
 }
 
@@ -2770,7 +2776,7 @@ nfsd4_encode_lock(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4_lo
 	else if (nfserr == nfserr_denied)
 		nfsd4_encode_lock_denied(resp, &lock->lk_denied);
 
-	encode_seqid_op_tail(resp, save, nfserr);
+	encode_seqid_op_tail(resp, save, nfserr, NULL);
 	return nfserr;
 }
 
@@ -2790,7 +2796,7 @@ nfsd4_encode_locku(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4_l
 	if (!nfserr)
 		nfsd4_encode_stateid(resp, &locku->lu_stateid);
 
-	encode_seqid_op_tail(resp, save, nfserr);
+	encode_seqid_op_tail(resp, save, nfserr, NULL);
 	return nfserr;
 }
 
@@ -2885,7 +2891,7 @@ nfsd4_encode_open(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4_op
 	}
 	/* XXX save filehandle here */
 out:
-	encode_seqid_op_tail(resp, save, nfserr);
+	encode_seqid_op_tail(resp, save, nfserr, NULL);
 	return nfserr;
 }
 
@@ -2897,7 +2903,7 @@ nfsd4_encode_open_confirm(struct nfsd4_compoundres *resp, __be32 nfserr, struct
 	if (!nfserr)
 		nfsd4_encode_stateid(resp, &oc->oc_resp_stateid);
 
-	encode_seqid_op_tail(resp, save, nfserr);
+	encode_seqid_op_tail(resp, save, nfserr, NULL);
 	return nfserr;
 }
 
@@ -2909,7 +2915,7 @@ nfsd4_encode_open_downgrade(struct nfsd4_compoundres *resp, __be32 nfserr, struc
 	if (!nfserr)
 		nfsd4_encode_stateid(resp, &od->od_stateid);
 
-	encode_seqid_op_tail(resp, save, nfserr);
+	encode_seqid_op_tail(resp, save, nfserr, NULL);
 	return nfserr;
 }
 
diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h
index 327552b..1401599 100644
--- a/fs/nfsd/state.h
+++ b/fs/nfsd/state.h
@@ -363,7 +363,6 @@ struct nfs4_openowner {
 	struct nfs4_ol_stateid *oo_last_closed_stid;
 	time_t			oo_time; /* time of placement on so_close_lru */
 #define NFS4_OO_CONFIRMED   1
-#define NFS4_OO_PURGE_CLOSE 2
 #define NFS4_OO_NEW         4
 	unsigned char		oo_flags;
 };
@@ -371,7 +370,7 @@ struct nfs4_openowner {
 struct nfs4_lockowner {
 	struct nfs4_stateowner	lo_owner; /* must be first element */
 	struct list_head	lo_owner_ino_hash; /* hash by owner,file */
-	struct list_head        lo_perstateid; /* for lockowners only */
+	struct list_head        lo_perstateid;
 	struct list_head	lo_list; /* for temporary uses */
 };
 
@@ -485,7 +484,7 @@ extern struct nfs4_client_reclaim *nfs4_client_to_reclaim(const char *name,
 							struct nfsd_net *nn);
 extern bool nfs4_has_reclaimed_state(const char *name, struct nfsd_net *nn);
 extern void release_session_client(struct nfsd4_session *);
-extern void nfsd4_purge_closed_stateid(struct nfs4_stateowner *);
+extern void release_last_closed_stateid(struct nfs4_openowner *);
 
 /* nfs4recover operations */
 extern int nfsd4_client_tracking_init(struct net *net);
diff --git a/fs/nfsd/xdr4.h b/fs/nfsd/xdr4.h
index 40e05e6..34766df 100644
--- a/fs/nfsd/xdr4.h
+++ b/fs/nfsd/xdr4.h
@@ -91,7 +91,8 @@ struct nfsd4_access {
 
 struct nfsd4_close {
 	u32		cl_seqid;           /* request */
-	stateid_t	cl_stateid;         /* request+response */
+	stateid_t	cl_stateid;         /* request */
+	struct nfs4_ol_stateid *cl_closed_stateid; /* response */
 };
 
 struct nfsd4_commit {
--
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