Re: [PATCH v2] nfsd: fix bug on nfs4 stateid deallocation

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On Fri, Apr 05, 2013 at 10:20:42AM -0400, J. Bruce Fields wrote:
> On Thu, Apr 04, 2013 at 10:04:03PM +0800, Yanchuan Nian wrote:
> > On Wed, Apr 03, 2013 at 02:55:08PM -0400, J. Bruce Fields wrote:
> > > On Wed, Apr 03, 2013 at 06:58:43PM +0800, Yanchuan Nian wrote:
> > > > On Mon, Apr 01, 2013 at 09:50:44PM -0400, J. Bruce Fields wrote:
> > > > > On Wed, Mar 13, 2013 at 11:04:54PM +0800, Yanchuan Nian wrote:
> > > > > > 2013/3/11 J. Bruce Fields <bfields@xxxxxxxxxxxx>
> > > > > > 
> > > > > > > On Mon, Mar 11, 2013 at 08:46:14AM +0800, ycnian@xxxxxxxxx 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.)
> > > > 
> > > 
> > > > This patch may cause memory leak in NFSv4.1. If the stateid released
> > > > is the last one in nfs4_openowner, nfs4_openowner will be deallocated
> > > > immediately, and NULL will be assigned to cstate->replay_owner at the
> > > > same time. In this situation encode_seqid_op_tail() cannot be called.
> > > > To avoid this problem, we can free the stateid just before or after
> > > > nfs4_opwnowner deallocation.
> > > 
> > > Yes, thanks for catching that!:
> > > 
> > >  	nfsd4_close_open_stateid(stp);
> > > -	close->cl_closed_stateid = stp;
> > > +	if (cstate->minorversion) {
> > > +		unhash_stid(&stp->st_stid);
> > > +		free_generic_stateid(stp);
> > > +	} else
> > > +		close->cl_closed_stateid = stp;
> > >  
> > >  	if (list_empty(&oo->oo_owner.so_stateids)) {
> > >  		if (cstate->minorversion) {
> > > 
> > > > Another question, cl_stateid in struct nfsd4_close will be returned to
> > > > the client, so original comment is right even though applying this
> > > > patch. Can this struct be commented like this.
> > > > 
> > > > struct nfsd4_close {
> > > >         u32             cl_seqid;           /* request */
> > > >         stateid_t       cl_stateid;         /* request+response */
> > > >         struct nfs4_ol_stateid *cl_closed_stateid; /* used during processing */
> > > 
> > > Agreed; done.  The result is the following (untested).
> > 
> > Yes, it works on my machine. Just the comment of cl_stateid in struct
> > nfsd4_close is still a little misleading.
> 
> Whoops, fixed.
> 
> Actually, I find encode_seqid_op_tail completely confusing, and I don't
> see why it's necessary--it would seem more straightforward to do the
> seqid bump in the procedure itself.  How about the following?

Sounds OK. I test it with some basic opens/closes. All goes well.
> 
> --b.
> 
> commit e58235072acd52ecab71d498b2b06633a2a0c376
> Author: J. Bruce Fields <bfields@xxxxxxxxxx>
> Date:   Mon Apr 1 16:37:12 2013 -0400
> 
>     nfsd4: cleanup handling of nfsv4.0 closed stateid's
>     
>     Closed stateid's are kept around a little while to handle close replays
>     in the 4.0 case.  So we stash them in the last-used stateid in the
>     oo_last_closed_stateid field of the open owner.  We can free that in
>     encode_seqid_op_tail once the seqid on the open owner is next
>     incremented.  But we don't want to do that on the close itself; so we
>     set NFS4_OO_PURGE_CLOSE flag set on the open owner, skip freeing it the
>     first time through encode_seqid_op_tail, then when we see that flag set
>     next time we free it.
>     
>     This is unnecessarily baroque.
>     
>     Instead, just move the logic that increments the seqid out of the xdr
>     code and into the operation code itself.
>     
>     The justification given for the current placement is that we need to
>     wait till the last minute to be sure we know whether the status is a
>     sequence-id-mutating error or not, but examination of the code shows
>     that can't actually happen.
>     
>     Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx>
> 
> diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
> index a9b707b..609e1e2 100644
> --- a/fs/nfsd/nfs4proc.c
> +++ b/fs/nfsd/nfs4proc.c
> @@ -415,7 +415,8 @@ out:
>  	nfsd4_cleanup_open_state(open, status);
>  	if (open->op_openowner)
>  		cstate->replay_owner = &open->op_openowner->oo_owner;
> -	else
> +	nfsd4_bump_seqid(cstate, status);
> +	if (!cstate->replay_owner)
>  		nfs4_unlock_state();
>  	return status;
>  }
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index 795b24d..bcd2339 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -720,6 +720,28 @@ dump_sessionid(const char *fn, struct nfs4_sessionid *sessionid)
>  }
>  #endif
>  
> +/*
> + * Bump the seqid on cstate->replay_owner, and clear replay_owner if it
> + * won't be used for replay.
> + */
> +void nfsd4_bump_seqid(struct nfsd4_compound_state *cstate, __be32 nfserr)
> +{
> +	struct nfs4_stateowner *so = cstate->replay_owner;
> +
> +	if (nfserr == nfserr_replay_me)
> +		return;
> +
> +	if (!seqid_mutating_err(ntohl(nfserr))) {
> +		cstate->replay_owner = NULL;
> +		return;
> +	}
> +	if (!so)
> +		return;
> +	if (so->so_is_open_owner)
> +		release_last_closed_stateid(openowner(so));
> +	so->so_seqid++;
> +	return;
> +}
>  
>  static void
>  gen_sessionid(struct nfsd4_session *ses)
> @@ -3702,6 +3724,7 @@ nfsd4_open_confirm(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
>  	nfsd4_client_record_create(oo->oo_owner.so_client);
>  	status = nfs_ok;
>  out:
> +	nfsd4_bump_seqid(cstate, status);
>  	if (!cstate->replay_owner)
>  		nfs4_unlock_state();
>  	return status;
> @@ -3785,31 +3808,12 @@ nfsd4_open_downgrade(struct svc_rqst *rqstp,
>  	memcpy(&od->od_stateid, &stp->st_stid.sc_stateid, sizeof(stateid_t));
>  	status = nfs_ok;
>  out:
> +	nfsd4_bump_seqid(cstate, status);
>  	if (!cstate->replay_owner)
>  		nfs4_unlock_state();
>  	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);
> @@ -3838,17 +3842,20 @@ nfsd4_close(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
>  					&close->cl_stateid,
>  					NFS4_OPEN_STID|NFS4_CLOSED_STID,
>  					&stp, nn);
> +	nfsd4_bump_seqid(cstate, status);
>  	if (status)
>  		goto out; 
>  	oo = openowner(stp->st_stateowner);
> -	status = nfs_ok;
>  	update_stateid(&stp->st_stid.sc_stateid);
>  	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;
> +
> +	if (cstate->minorversion) {
> +		unhash_stid(&stp->st_stid);
> +		free_generic_stateid(stp);
> +	} else
> +		oo->oo_last_closed_stid = stp;
>  
>  	if (list_empty(&oo->oo_owner.so_stateids)) {
>  		if (cstate->minorversion) {
> @@ -4270,6 +4277,7 @@ nfsd4_lock(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
>  out:
>  	if (status && new_state)
>  		release_lockowner(lock_sop);
> +	nfsd4_bump_seqid(cstate, status);
>  	if (!cstate->replay_owner)
>  		nfs4_unlock_state();
>  	if (file_lock)
> @@ -4439,6 +4447,7 @@ nfsd4_locku(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
>  	memcpy(&locku->lu_stateid, &stp->st_stid.sc_stateid, sizeof(stateid_t));
>  
>  out:
> +	nfsd4_bump_seqid(cstate, status);
>  	if (!cstate->replay_owner)
>  		nfs4_unlock_state();
>  	if (file_lock)
> diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
> index 700de01..a5e8a64 100644
> --- a/fs/nfsd/nfs4xdr.c
> +++ b/fs/nfsd/nfs4xdr.c
> @@ -1701,28 +1701,6 @@ static void write_cinfo(__be32 **p, struct nfsd4_change_info *c)
>  								\
>  	save = resp->p;
>  
> -/*
> - * Routine for encoding the result of a "seqid-mutating" NFSv4 operation.  This
> - * is where sequence id's are incremented, and the replay cache is filled.
> - * 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)
> -{
> -	struct nfs4_stateowner *stateowner = resp->cstate.replay_owner;
> -
> -	if (seqid_mutating_err(ntohl(nfserr)) && stateowner) {
> -		stateowner->so_seqid++;
> -		stateowner->so_replay.rp_status = nfserr;
> -		stateowner->so_replay.rp_buflen =
> -			  (char *)resp->p - (char *)save;
> -		memcpy(stateowner->so_replay.rp_buf, save,
> -			stateowner->so_replay.rp_buflen);
> -		nfsd4_purge_closed_stateid(stateowner);
> -	}
> -}
> -
>  /* Encode as an array of strings the string given with components
>   * separated @sep, escaped with esc_enter and esc_exit.
>   */
> @@ -2667,7 +2645,6 @@ 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);
>  	return nfserr;
>  }
>  
> @@ -2770,7 +2747,6 @@ 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);
>  	return nfserr;
>  }
>  
> @@ -2790,7 +2766,6 @@ 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);
>  	return nfserr;
>  }
>  
> @@ -2885,7 +2860,6 @@ nfsd4_encode_open(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4_op
>  	}
>  	/* XXX save filehandle here */
>  out:
> -	encode_seqid_op_tail(resp, save, nfserr);
>  	return nfserr;
>  }
>  
> @@ -2897,7 +2871,6 @@ 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);
>  	return nfserr;
>  }
>  
> @@ -2909,7 +2882,6 @@ 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);
>  	return nfserr;
>  }
>  
> @@ -3567,6 +3539,7 @@ __be32 nfsd4_check_resp_size(struct nfsd4_compoundres *resp, u32 pad)
>  void
>  nfsd4_encode_operation(struct nfsd4_compoundres *resp, struct nfsd4_op *op)
>  {
> +	struct nfs4_stateowner *so = resp->cstate.replay_owner;
>  	__be32 *statp;
>  	__be32 *p;
>  
> @@ -3583,6 +3556,11 @@ nfsd4_encode_operation(struct nfsd4_compoundres *resp, struct nfsd4_op *op)
>  	/* nfsd4_check_drc_limit guarantees enough room for error status */
>  	if (!op->status)
>  		op->status = nfsd4_check_resp_size(resp, 0);
> +	if (so) {
> +		so->so_replay.rp_status = op->status;
> +		so->so_replay.rp_buflen = (char *)resp->p - (char *)(statp+1);
> +		memcpy(so->so_replay.rp_buf, statp+1, so->so_replay.rp_buflen);
> +	}
>  status:
>  	/*
>  	 * Note: We write the status directly, instead of using WRITE32(),
> diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h
> index 7674bc8..13ec485 100644
> --- a/fs/nfsd/state.h
> +++ b/fs/nfsd/state.h
> @@ -355,7 +355,6 @@ 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;
>  };
> @@ -363,7 +362,7 @@ 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 */
>  };
>  
> @@ -477,7 +476,6 @@ 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 put_client_renew(struct nfs4_client *clp);
> -extern void nfsd4_purge_closed_stateid(struct nfs4_stateowner *);
>  
>  /* 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..3b271d2 100644
> --- a/fs/nfsd/xdr4.h
> +++ b/fs/nfsd/xdr4.h
> @@ -623,6 +623,7 @@ extern __be32 nfsd4_test_stateid(struct svc_rqst *rqstp,
>  		struct nfsd4_compound_state *, struct nfsd4_test_stateid *test_stateid);
>  extern __be32 nfsd4_free_stateid(struct svc_rqst *rqstp,
>  		struct nfsd4_compound_state *, struct nfsd4_free_stateid *free_stateid);
> +extern void nfsd4_bump_seqid(struct nfsd4_compound_state *, __be32 nfserr);
>  #endif
>  
>  /*
--
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